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Grapevine Red Blotch Virus in Comparison to Grapevine Leafroll-Associated Virus

By
Justin Tanner | Ph.D., UCCE Viticulture Farm Advisor, San Joaquin and Stanislaus Counties
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Visual symptoms of Grapevine Red Blotch Virus showing in older leaves of an infected vine. Notice healthy vines on either side showing yellowing leaves as the vines prepare to drop the leaves (all photos by J. Tanner, courtesy University of California.)

Grapevine Red Blotch associated Virus (GRBaV) is the causal viral agent responsible for Grapevine Red Blotch Disease. This pathogen negatively impacts grape production by reducing fruit quality and yield. It can cause several physiological changes in vines, including changes in leaf color, reduced ripening speed and decreased fruit quality from reduced sugar and anthocyanin accumulation in the grapes.

This reduction in fruit quality can lead to reduced market value, affecting the profitability of an impacted vineyard. The degree to which GRBaV will impact fruit quality and yield can vary from year to year within a vineyard but increases with the percent of infected vines contributing to the harvest. The exact mechanism by which Red Blotch reduces sugar accumulation in grape berries is still unclear; however, the available evidence suggests the virus affects the expression of genes involved in sugar transport and metabolism as well as in hormone signaling pathways that regulate sugar accumulation in grape berries.

Red Blotch disease was first discovered in Napa Valley, Calif. in 2008 when it was realized to be a new disease separate from leafroll which also causes similar red leaf symptoms as well as a reduction in fruit quality and yield. The similarities between the effects of Red Blotch and leafroll viruses likely played a role at masking the presence of Red Blotch virus until efficient virus screening techniques for GRBaV were commonly employed. At the point of its discovery, Red Blotch disease was not a newly emerged viral disease but rather a viral disease new to our recognition as a viral disease.

Due to the misidentification of GRBaV in symptomatic grapevines, the virus may have been widely spread across California by the time a screening procedure was developed to identify its presence in plant tissues. To this point, Red Blotch virus was detected in herbarium samples collected several decades before the formal recognition of the virus. Red Blotch virus is the only member of the genus Grablovirus within the family Geminiviridae and has been separated into at least two clades of distinct strains of the virus. While originally recognized in California, it has since been found in several grape-growing regions worldwide.

Grapevine Leafroll-Associated Disease, on the other hand, is caused by one of six viruses from the family Closteroviridae. Grapevine Leafroll-associated Virus (GLRaV) is one of the most important viral diseases affecting grape production worldwide. Of the six viruses associated with leafroll disease, GRLaV-3 in the genus Ampelovirus is the most predominant; GLRaV-2 has also been noted as impacting large numbers of California’s vineyards.

Figure 1. Visual symptoms of Grapevine Red Blotch Virus showing in older leaves of an infected vine. Notice healthy vines on either side showing yellowing leaves as the vines prepare to drop the leaves (all photos by J. Tanner, courtesy University of California.)

Leaf Symptoms
Often described as beautiful fall color by visitors to the vineyard around harvest time, the development of red leaves in red grape varieties is a sign the vines are not healthy. The most prominent visual symptoms of Red Blotch are reddish-pink blotches or patches that appear on the leaves of infected red grape varieties. These blotches usually appear later in the growing season, usually after véraison, first appearing on older leaves near the bottoms of shoots and later developing on leaves higher up the shoot. These blotches are irregular in shape and often have a mosaic pattern.

Foliar symptoms of GRBaV and GLRaV are visually similar, and both result in red- or yellow-toned tissue of the leaf blade depending on the grape cultivar. With Red Blotch, the leaf veins also turn red which is in contrast with leafroll in which the veins remain green. Another subtle difference is that Red Blotch does not distort the shape of the leaf causing the leaf blade to remain flat while Leafroll-associated viruses can cause some leaf blades to roll down along the margins, resulting in a downward curl. When a vine has Grapevine Red Botch Virus and a Grapevine Leafroll-associated Virus, leaf symptoms usually present as typically expected for Grapevine Leafroll associated Viruses with leaves showing green veins and some degree of leaf rolling.

Towards the end of the season, symptomatic leaves from either virus may turn completely red, complicating visual diagnosis. In white varieties of grape, both viruses are much less conspicuous as the leaves do not turn red but may present in a subtle, yellow-chlorotic, patchy pattern.

Figure 2. Red leaf virus symptoms on Cabernet Sauvignon. Grapevine Red Blotch Virus (left) showing mosaic pattern of red patches with red leaf veins, Grapevine Leafroll-associated Virus (right) showing red patches and green veins.

Virus Spread Through Infected Material
Both viruses can be transmitted through propagation of infected planting material. The use of CDFA-certified virus-tested vines is an important initial step in excluding viruses in your vineyard. As there is currently no cure for vines once infected with Red Blotch or Leafroll, the use virus-free planting materials and the removal of infected vines is the first line of defense in virus management. Scouting and monitoring vineyards for red leaf symptoms in the fall is essential for early detection.

PCR testing can be used to confirm viral presence in visually identified symptomatic vines if there is any doubt about the symptoms and is especially useful for confirming virus status of white grape cultivars. Once identified, infected vines should be rogued from the vineyard to reduce pathogenic inoculum and prevent them from serving as a source of virus that could inflect healthy vines. Vines identified in the late part of the growing season should be removed before the start of the next season to minimize the spread of the virus by insect vectors.

PCR-based testing methods are the standard for determining virus status of individual vines with a high degree of accuracy but becomes cost-prohibitive at commercial scales. New approaches to virus identification are being developed to allow for screening of vines rapidly and accurately within a whole vineyard. The use of drone-based hyperspectral imaging has been demonstrated to be more accurate at identifying vines infected with Red Blotch or Leafroll compared to visual scouting by experts when coupled with machine learning methods.

Figure 3. Signs of three-cornered alfalfa hopper feeding damage causing leaf girdling (highlighted with arrows.) This sign does not indicate virus infection. Notice the red color of the girdled leaf compared to other leaves on the shoot.

Another approach in development involves the use of dogs trained to detect virus in vines. Other methods in development include non-destructive wavelength transmission and reflection to identify foreign organisms within the vine without damaging the plant.

Virus Spread by Insect Vectors
The three-cornered alfalfa hopper (Spissistilus festinus, TCAH) is currently the only confirmed vector of Red Blotch virus. It is an insect that can feed on many plant species including grapevines and is widely distributed throughout the U.S. Plants such as alfalfa and other legumes serve as the preferred hosts for TCAH; however, as these plants dry up over the season, TCAH will migrate onto less preferred hosts such as grapevine.

This pattern of micro-migration may be particularly problematic in vineyards where annual cover crop decline occurs near the beginning of vegetative growth for grapevines. TCAH can acquire GRBaV from feeding on infected plants and subsequently spread the virus to healthy vines. However, studies investigating the vector-capacity of TCAH have found they are not good at spreading the virus. TCAH is a circulative and non-propagative host where the virus does not replicate within the insect but is transferred into the salivary glands. TCAH requires an extended acquisition period of about 10 days to uptake the virus while feeding on infected vines followed by an extended inoculation access period of about four days of feeding on healthy vines to spread the virus.

As grapevines are not the preferred host, TCAH populations usually remain low within vineyards and are mainly driven by the presence of legumes in cover crops. Timely management of cover crops by tillage before TCAH reaches adulthood may help reduce population sizes and limit virus spread by the alfalfa hopper. Additionally, removing unmanaged grapevines from the perimeter of vineyard areas is helpful as these vines can act as virus reservoirs and are particularly at risk of infection in riparian areas where insect populations may be higher. The work of identifying and confirming insect vectors of Red Blotch is ongoing, and there are many other insects identified as potential vectors currently under investigation.

Figure 4. Vine mealybugs on the trunk of a grapevine revealed after removal of loose bark. Notice how the mealybugs are surrounded by ants.

Due to the feeding nature of TCAH, alternative plant hosts of GRBaV should be identified in California and managed to reduce potential inoculum sources near vineyards. To date, few endemic plant species within California have been tested to see if they can harbor GRBaV. However, researchers tested 13 species of woody, herbaceous plants from riparian areas which tested positive for GRBaV and identified two positive hosts: Himalayan Blackberry and a wild grapevine hybrid (V. californica x V. vinifera). In certain regions of California, a higher number of inoculum sources and alternative hosts for GRBaV may lead to higher pathogen pressure in vineyards with Red Blotch symptoms.

With the potential for other insect vectors being able to transmit GRBaV, it is important to understand which plants in vineyard-adjacent ecosystems can increase risk of Red Blotch transmission into grapevines.

For Leafroll, several species of mealybugs (family Pseudococcidae) and scale insects (family Coccoidea) have been shown to be competent vectors. However, the most important vector of GLRaV is the vine mealybug (Planococcus ficus), an invasive species first detected in California in the mid-1990s which can have up to seven generations in a single growing season. The vine mealybug requires a period of as little as 15 minutes of feeding on an infected vine to acquire Leafroll. Because of the efficiency of virus uptake by the vine mealybug and the rapid nature of its reproductive strategy, in areas where vine mealybug is present, Leafroll has the potential for rapid spread.

The most effective management strategy for vine mealybugs involves an integrated approach which includes the use of biological, cultural and chemical control methods as well as managing ants which protect mealybugs from their natural enemies. The parasitoid wasp Anagryus pseudococci and other beneficial species have been shown to successfully reduce vine mealybug infestations to manageable levels. A detailed guide to this approach is available at ipm.ucanr.edu/agriculture/grape/vine-mealybug/.

In summary, both Red Blotch and Leafroll viruses can cause significant impacts to fruit quality and yield. Both viruses will cause symptoms of red leaves in red grape cultivars; however, slight differences between these symptoms can be visually identified and useful in distinguishing between the two. Once symptomatic vines are identified, PCR testing can confirm virus status. While both viruses can be vectored through the propagation of infected material, there’s great differences in the efficiency of virus spread by insect vectors.

For Red Blotch, the three-cornered alfalfa hopper, requires an unusually long acquisition time of about 10 days of feeding on infected vines before it can spread the virus compared to the alarmingly quick uptake of Leafroll by the vine mealybug in around 15 minutes. Other potential insect vectors of Red Blotch have been identified and are currently under investigation. Additionally, the three-cornered alfalfa hopper usually doesn’t reach high populations within vineyards as the grapevine is not it’s preferred host plant; while the vine mealybug, on the other hand, due to its prolific reproductive strategy has the potential to reach very high numbers if left untreated in the vineyard.

Once infected with Red Blotch or leafroll, there is no cure, and removal of the vine is the only sure way to prevent future spread to neighboring vines. Monitoring GRBaV symptomatic grapevines and removing them from the vineyard quickly may be the best approach to limiting the spread of Red Blotch at the moment. With research ongoing and without a clear understanding of how the virus can rapidly spread, reducing inoculum sources is a proven, preventative strategy.

Leapfrogging from Solar to a Microgrid Domaine Carneros Seeks Energy Independence

By
Pam Strayer | Contributing Writer
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Computer-generated images for Domaine Carnero’s microgrid project. In conjunction with the winery’s solar vendors, a microgrid is not only feasible but also cost effective (photos courtesy Domaine Carneros.)

At 3:20 am on Aug. 24, 2014, a 6.0 magnitude (severe) earthquake shook the Carneros region near Domaine Carneros, located on Duhig Road, just a few miles inland from San Francisco Bay.

Downtown, the classic 1901 Goodman Library, home to the Napa County Historical Society, was significantly damaged. Though only one person died, area damages were estimated at $1 billion. The South Napa Quake was the largest earthquake in the San Francisco Bay Area since the famed 6.9 Loma Prieta earthquake in 1989.

The earthquake hit just two weeks after picking for 2014 vintage sparkling wine was underway.

Importantly from the perspective of the wine industry, the earthquake interrupted power. More than 69,000 people, including many wineries, were without power.

Fast forward to 2017 when a series of fires hit Napa and Sonoma. The 2017 fires alone caused $14.5 billion in damages. In response, in 2018 Pacific Gas & Electric (PG&E) began implementing Public Safety Power Shutoffs (PSPS) when fire danger and winds were high.
Again, wineries were not guaranteed power, especially during critical harvest periods when a lot of power is used for cooling and operations.

A Novel Solution
For Domaine Carneros, a sparkling wine producer owned by the famous French Champagne house Taittinger, the events sparked their interest in finding a more stable energy solution. They had already installed the largest solar array of any winery in the world in 2003. But they did not have a way to store solar energy.

“When we first discussed the project in 2018 and 2019, our motivation was to create energy independence in a power outage having recently experienced the 2014 earthquake and the 2017 fires,” said CEO Remy Cohen, who presented in-depth details about the winery’s analysis and planning efforts April 5 at Beringer Winery during the first day of Napa Green’s six-day climate summit Rise Green.

Working with Stacey Ellis, capital projects manager, the two, in conjunction with their solar vendors, found a microgrid was not only feasible but also cost effective. Initially, they were looking at a payback of 11 years, but subsequent PG&E rate increases and passage of new federal legislation sweetened the pie.

“PG&E has increased rates quicker and more than the model, so we anticipate a shorter ROI now,” said Cohen. The project costs nearly $1.9 million but federal investment tax credits (ITC) and state Self-Generation Incentive Program (SGIP) incentives of $576,000 will kick in, in addition to the winery’s net utility bill savings. The winery will also no longer need to rent a standby generator.

Domaine Carneros CEO Remy Cohen presented in-depth details about the winery’s microgrid analysis and planning efforts at Napa Green’s six-day climate summit Rise Green (photo by P. Strayer.)

“The combination of the existing rooftop solar and the microgrid will allow us to generate 75% to 80% of the winery’s annual energy use,” she said.

The team looked at several alternatives during the planning process.

“The initial thought was to purchase just the generator and transfer switch that would shut off the grid and start up the generator, but that cost was $500,000 to $1 million and would sit most of the time just waiting for an outage and could take years to pay itself back,” she said. “The microgrid is operating and saving us money 365 days a year for an improved ROI and resiliency.”

Projected PG&E tax increases also make the case for a microgrid. Rates increased 16% in 2022 and are projected to rise dramatically over the next few years. Increases are projected to rise 18% in 2023 and more in the next three years, totaling a 32% increase by 2026, according to the PUC’s fact sheet.

While many businesses have used microgrids to lower energy costs by what is called “peak shaving,” or using solar during PG&E’s highest rate periods, typically wineries have shied away from installing a microgrid due to high energy use at harvest.

But Cohen said their new system will be able to carry larger loads with a generator as backup.

“The battery can handle our full energy load for two hours. Therefore, it will operate longer than when we are operating below peak load. So, if the power goes out during harvest and we are operating at peak load, the battery will provide at least a couple hours of our energy demand and then there is a seamless transition to the generator.

“Although we are not completely independent from using a generator, the microgrid and battery will reduce our reliance on the generator and fuel consumption.

“Eventually, the winery may be able to improve the efficiency of our operations,” she added, “or get a battery with more capacity to reduce our generator reliance even further. The generator will handle any loads over the battery capacity. But most of the load will be covered by the solar and battery during the day and the generator will only be needed during the evening and at night when we are ‘islanding.’”

Why do the project now? Cohen said the 30% federal tax credit was one reason. But there are others.

“The battery technology is evolving rapidly so batteries can store more now in a smaller footprint than before,” she added.

Harnessing Beneficial Microbes Injectable Biocontrol Agents Show Promise in Managing Pierce’s Disease Bacterium

By
Vicky Boyd | Contributing Writer
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Blue-green sharpshooters frequent riparian areas near vineyards. Although they are efficient vectors of the Pierce’s disease bacterium, they are not strong flyers (photo by Alex Purcell, UC Berkeley.)

With a dearth of products to manage Pierce’s disease until recently, grape growers instead focused on controlling the insects that spread the disease and removing infected vines.
But federal and California registrations of the biopesticide XylPhi-PD from Palo-Alto-based A&P Inphatec in 2019 gave organic and conventional growers an option that targets Pierce’s disease itself.

The product’s active ingredients are a mix of two bacteriophages, also known as phages, said Josie Hugie, a PCA and consultant to A&P Inphatec. These naturally occurring viruses target and invade specific bacteria, killing them in the process and reproducing more phages. At the same time, they leave other microorganisms, other cells and their hosts unharmed. In the case of PD, the phages target the causal bacterium Xylella fastidiosa.
Ongoing University of California field trials that are examining three naturally occurring bacteria as PD biocontrol agents also are yielding promising results.

The cause for concern is the financial gravity of the disease. In 2014, a UC study estimated Pierce’s disease cost California about $104.4 million per year in vine losses, industry assessments, compliance costs and expenditures by government agencies. Of that, growers bore $56.1 million in lost production and vine replacement expenses.

Texas A&M Research Outcome
Otsuka Pharmaceutical began work for controlling X. fastidiosa in 2007, and in 2010 contacted Carlos Gonzalez, a professor in Texas A&M College of Agriculture and Life Sciences’ Department of Plant Pathology and Microbiology. This led to a collaboration in phage research, which eventually became the first path to isolate phages for X. fastidiosa control.

Gonzalez also is a member of the Texas A&M AgriLife Center for Phage Technology, which is exploring unique therapies to treat bacterial infections of plants, animals and humans.
After conducting extensive greenhouse and field testing, Texas A&M licensed the PD phages to Otsuka Pharmaceutical Co., the parent of A&P Inphatec, to commercialize and market. In addition to being state and federally registered, the product is Organic Materials Review Institute listed for use on certified organic vineyards.

Glassy-winged sharpshooters have a wide host range and are strong flyers. As a result, they can carry the Pierce’s disease bacterium and spread it throughout a vineyard (photo by Reyes Garcia III, USDA-ARS.)

Vine Treatment
Growers inject XylPhi-PD into the xylem using the Pulse Xyleject device that resembles a cattle vaccination gun. The rate depends on the size of the vine. Israel Luna, A&P Inphatect services rep, recommended two injections of 0.08 milliliters each made at the base of the trunk of young vines or replants, staggering the location. For mature vines, he recommended four injections of 0.08 ml each, with two at the base of the trunk and one in each cordon near the trunk.

A 100 ml bottle can treat about 600 young vines or 300 mature vines. Within California, XylPhi-PD is available through Wilbur-Ellis Co. and Helena Agri-Enterprises (except in four counties: Napa, Sonoma, Lake and Mendocino).

Depending on PD pressure, Luna recommended two to three treatments per season spaced four to six weeks apart. The first injection should be given at flowering or 8 to 10 weeks after the vines break dormancy.

“A lot of our current users with blue-green sharpshooter on the coast use it twice per year, but it can be tailored on a case-by-case basis like whether a vineyard has high PD pressure or the vines are near a riparian area,” Hugie said.

But she was quick to point out the bacteriophages are not cure-alls and may not help vines that are too far gone.

Wood on new canes matures irregularly, producing patches of green surrounded by mature brown bark creating “green islands” (photo by Akif Eskalen, UCCE.)

“If you’re treating vines that are already infected, you can’t cure them all,” she said. “Tyloses will block the way for the phages. You have to have realistic expectations.”

But in vineyards that had no PD, Hugie said they’ve successfully protected more than 99% of the vines from new disease symptoms.

Since 2019, several trials have been conducted in North Coast vineyards with XylPhi-PD, said Vincent Avila, A&P distributor sales and technical support representative. One set involved three vineyards on the Russian River and one on Dry Creek that had PD hotspots.
In each vineyard, a block was left untreated for the control, one block received treatments for two years (with no treatment in year one) and a third received treatments for three years.

Matchsticking describes the Pierce’s disease symptom where the leaf withers and drops off but the petiole remains attached to the stem (photo by Akif Eskalen, UCCE.)

After three years, Avila said they saw a 55% reduction in detectable X. fastidiosa for all vines and an 84% prevention efficacy with no new PD cases in the three-year treated group. There was only one new case in the two-year treated group. Visual symptoms were verified using PCR testing, a type of genetic fingerprinting.

Within these trials, a vineyard with PD found a 17% yield increase in vines treated three years and a 10% yield increase for vines treated two years compared to an untreated control.

New leaves become chlorotic between leaf veins, and scorching appears on older leaves (photo by Akif Eskalen, UCCE.)

Hunt for Other Biocontrol Agents
Dr. Akif Eskalen, a UCCE plant pathology professor, began a field trial near Davis in 2021 testing 10 different treatments. Among them are XylPhi-PD and three different biocontrol bacteria injected individually. In addition, each of the three bacteria were injected in combination with the phages. Of the treatments, only XlyPhi-PD is commercially available and registered for use in California grapes.

Eskalen said he decided to focus on organic and biological agents because synthetic products such as antibiotics are inefficient or not feasible at managing xylem-limiting pathogens.

“It’s very difficult to control a systemic pathogen like Xylella because you need something that’s systemic, and many of the pesticides are not systemic and will not move up and down [the xylem],” he said. “Because of that, we were very limited in trying to find alternate applications.”

Dr. Steve Lindow, professor emeritus with UC Berkeley Department of Plant and Microbial Biology, led a team that identified one of the beneficial bacterium, Paraburkholderia phytofirmans. In previous experiments, it appeared to induce disease resistance in grape plants.

The other two beneficial bacteria were discovered by Dr. Philippe Rolshausen with the UC Riverside Department of Botany and Plant Sciences while analyzing beneficial microbes in non-symptomatic grapevines growing in PD-infected symptomatic vineyards.

Eskalen’s trial is being conducted on 12-year-old Cabernet Franc vines in a vineyard with no history of PD located near the UC Davis campus in Solano County.

Pierce’s disease also can cause shrivel of grape clusters (photo by Akif Eskalen, UCCE.)

Except for the untreated control, all of the grapevines were inoculated with X. fastidiosa May 4, 2022. Depending on the treatment, the biocontrol agents were injected either one day before inoculation and/or seven days after inoculation. He also included a treatment that involved no biocontrol agent.

In August, Eskalen visually rated them for percentage PD foliar symptoms for five straight weeks.

One year into the trial, he called the results “interesting.” Vines treated with three injections of XylPhi-PD following label recommendations had 50% fewer foliar symptoms than the inoculated-only vines.

All three experimental biocontrol agents worked better when combined with XylPhi-PD than they did alone. And a combination of biocontrol agent 1/XylPhi-PD and a combination of biocontrol agent 3/XylPhi-PD performed the best of all treatments.

“This is not 100% control,” Eskalen said. “It’s a significant reduction of the infestation, and we’ve seen a reduction in the symptoms in our one-year trial.”

He emphasized the results are preliminary, and he plans to repeat the trial this year and next to see if the trends continue. But Eskalen said they were too promising not to discuss at least as preliminary findings.

Israel Luna of Inphatec shows off the CO2-powered Pulse Xyleject device used to inject the bacteriophages into grapevines (photo by V. Boyd.)

The PD-Sharpshooter Relationship
X. fastidiosa is spread by sharpshooters, a group of leafhoppers that includes blue-green sharpshooters, red-headed sharpshooters and glassy-winged sharpshooters.

As they insert their straw-like stylet to feed in the grapevine’s xylem vessels, or water-conducting tissue, infected sharpshooters inject bacteria. The plants respond with defense mechanisms that include tyloses, which are glue-like substances that dam up vascular tissue to prevent further damage, and gums. Together with the bacteria, they may block the xylem, resulting in wilting and possibly vine death.

During feeding, non-infected sharpshooters also may acquire X. fastidiosa from infected vines that serve as disease reservoirs.

PD symptoms may include marginal leaf scorching, fruit shrivel and “match-sticking” where leaves drop but the petioles remain. Infected plants also may look drought stressed, but a yellow or red-brown band between green and scorched areas on leaves is absent in drought-stressed vines. In addition, symptoms may vary widely, depending on the grape variety and when vines were initially infected.

Blue-green sharpshooters are very efficient vectors of the PD bacterium, but they aren’t strong fliers, said Rodrigo Krugner, a USDA-ARS research entomologist in Parlier. In the North Coast, they frequent riparian areas. As grapevines leaf out, they’ll move into vineyards but typically remain in only the first few rows closest to riparian areas.
Glassy-winged sharpshooters, on the other hand, are not efficient vectors of PD, he said. But they’re strong fliers and have an extensive host range. As a result, PD-infected vines may be found throughout a vineyard.

Pierce’s disease has been reported in California as far back as the 1880s. But it wasn’t until the late 1990s, about 10 years after the glassy-winged sharpshooter arrived in the state likely from the Southeast, that PD began to grab headlines. It turned out the newcomer had the potential to spread X. fastidiosa much farther and faster than native sharpshooters.
Currently, glassy-winged sharpshooters are found mainly in Southern California and the southern San Joaquin Valley.

A Taste of Something More

By
Catherine Merlo | Contributing Writer
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Appointment-only wine tastings have largely replaced visitor walk-ins (photo courtesy Paso Robles Wine Country Alliance.)

Chad Melville wasn’t happy when pandemic restrictions forced his family’s winery in Santa Barbara County to change the way it conducted wine tastings for visitors.

Like businesses everywhere, Melville Winery shut down its public-facing operation in March 2020. Two months later, it was one of the first wineries in California to re-open its tasting business. But instead of welcoming walk-in visitors into its beautiful, Mediterranean-style headquarters near Lompoc, Melville Winery had to limit its tastings to by-appointment only.
Moreover, the scheduled guests couldn’t sit indoors or stand together at the interior L-shaped bar where they might be more vulnerable to contracting COVID-19. Due to social distancing requirements, they had to be seated outdoors in small groups. In the pandemic’s early days, as wine-country tourism slumped, Melville worried.

As the months unfolded, however, he was surprised to discover his visitors were enjoying the new tasting model. The seating on the grass patio gave guests a panoramic view of sky and nearby hills, and they could practically touch the family’s 120 acres of estate vineyards, located in the Santa Rita Hills appellation, whose grapes produced the Pinot Noirs and Chardonnays they were sampling.

Tastings became slower, more in-depth and one-on-one with Melville and his small tasting team. Guests could learn more about the winery’s hand-crafted, organically grown wines. Visits now stretched to 90 minutes, more than twice as long as pre-pandemic walk-in stops.

“COVID forced us to change, but we quickly learned how beneficial the new tasting model was,” said Melville, head winegrower for the family-owned vineyards and winery. “We have a better connection with customers that we didn’t before. That’s huge.”

Wine Tasting Evolves
Wineries across California have made the same discovery. As the pandemic moves into the rear-view mirror, vintners in the nation’s top wine-producing state are adjusting to what they’ve learned about consumer preferences over the past three years. Many wineries have kept the by-appointment-only tastings that emerged during COVID-19 controls. Some have evolved to a hybrid of scheduled and walk-in visits.

At the same time, winemakers are focusing on providing a more specialized experience for discerning wine consumers. Where visitors once stopped in wine country to taste and purchase wine, today’s wine tourists are looking for something more, Rob McMillan noted in the “State of the U.S. Wine Industry 2023” report from Silicon Valley Bank (the bank has since been acquired by First Citizens Bank.)

They’re often staying in nearby lodging, then making only a couple of stops a day at wineries, added McMillan. In turn, wineries are sitting down with their guests for longer, more personalized presentations.

“Tasting has become more high touch,” agreed Chris Taranto, communications director with the Paso Robles Wine Country Alliance. “There’s more time to taste and build a relationship with the winery to learn about its brand and story.

“Wineries like appointment-only tastings,” he added. “Each guest is given attention, and that gives a good experience. And it helps lock in more sales and potential wine-club membership.”

The consumer’s onsite experience is vital to wineries. The average winery today receives more than 30% of its total revenue from tasting room sales, said McMillan.

Direct Access, Deeper Experience
The direct-to-consumer, or DTC, tasting model is especially important to small wineries like Crown Point Vineyards in Santa Barbara County’s Santa Ynez Valley. The winery produces wines for the super-luxury category, where wine sells for $100 to $200 a bottle. Known for its Cabernet Sauvignon, Crown Point produces 2,500 cases of wine each year. That’s considerably smaller than the 5,000-case average among U.S. bonded wineries.

“The tasting experience and engaging with the winery team is still the most important fundamental to the financial well-being of a winery,” said AJ Fairbanks, estate director for Crown Point Vineyards. “Sixty percent of our revenue derives from the DTC model.”
Since its founding in 2013, Crown Point has only offered by-appointment tasting experiences. The extended time visitors spend with Crown Point’s team is a key opportunity to sell its limited production.

The tasting experience is fundamental to a winery’s financial well-being, says AJ Fairbanks of Crown Point Vineyards (photo courtesy Crown Point Vineyards.)

“By-appointment experiences typically outperform walk-ins in terms of customer satisfaction, sales efficiency and member recruitment,” said Fairbanks.

Scheduled tastings make it easier to manage the staff schedule, which helps with employee fulfillment and retention, he said. The winery can thoroughly collect customers’ data before they arrive. It can then slightly personalize the experience to enhance the tasting execution.

The more specialized, intimate tasting experience is “working out extremely well for us,” Fairbanks said. “We saw a 21% increase in traffic from 2021 to 2022.”

Moving Outdoors
At Tablas Creek Vineyard, outside of Paso Robles, pandemic-forced adjustments are now standard in the tasting room.

“The biggest change is that all tastings are now seated flights,” said Jason Haas, general manager, partner and proprietor. “And before, we didn’t do tastings outside.”

Like other businesses, Tablas Creek closed for three months in the spring of 2020. The winery reopened its tasting operation in June of that year with newly set up tasting bars, tables, chairs and umbrellas, all outside. It offered no indoor pourings for over a year.
When the winery was allowed to re-open its indoor tasting room in June 2021, “we decided to replicate the outside experience to inside,” Haas said.

Chad Melville, here at his family’s winery in Santa Barbara County, has learned from pandemic-led changes (photo courtesy Melville Winery.)

During that year of forced outdoor tasting, he and his team had learned that packing people into an inside tasting room, as was typical before the pandemic, hadn’t been all that visitor friendly.

“We hadn’t been taking care of them as much as we thought because we were too busy,” he said. “If people come to a winery, they want more than just a glass of wine; they want the story.”

Tablas Creek’s decision to spend more time with guests comes even as the pandemic’s disruptions are still being felt across the wine-tasting sector. In 2022, Tablas Creek welcomed 28,000 guests, 3,000 less than in 2019. It’s not alone in lower tasting room numbers; most wineries still aren’t back to pre-pandemic levels.

Another reason Tablas Creek sees fewer guests is that it has lowered its tasting accommodation to just 175 visitors per day. It now spaces out its reservations two hours apart. Guests have their own space at either indoor or outdoor tables.

“We have found they enjoy it more,” said Haas. “They buy more wine and are more likely to sign up for one of our wine clubs.”

All that impacts the bottom line at Tablas Creek. One-fourth of its total volume of wine sold and 35% of its total revenue come from wine bought during onsite visits. Even more important, 80% of its wine club signups happen in the tasting room.

“People want more than just a glass of wine” in their tasting experience, says Jason Haas of Tablas Creek Winery (photo by C. Merlo.)

“The tasting room is critical to us,” Haas said. “It’s where we touch the most people. If they leave with a great experience, they’re more likely to buy our wine.”

A Future with More DTC Experiences
Going forward, Napa Valley-based Cakebread Cellars is “looking at more creative ways” to expand its tasting reach, said Misty Roudebush Cain, vice president of direct-to-consumer and hospitality for the winery.

At its main location in Rutherford, for example, Cakebread Cellars has introduced a “library tasting experience” to celebrate its 50th anniversary during 2023. This includes a curated selection of red and white wines from the family’s vault of past vintages as well as current releases, paired with culinary bites.

Misty Cain of Cakebread Cellars says the Napa Valley winery will evolve its virtual wine tastings, which emerged during the pandemic (photo courtesy Cakebread Cellars.)

In addition, Cakebread Cellars has launched a cabernet sauvignon tasting experience “for those serious about the varietal,” Cain said. The winery has also re-introduced a family tasting offering “to help make planning a little easier for those traveling to wine country with children,” she added.

The family-owned vintner has also joined with other Napa Valley wineries in Collective Napa Valley, a philanthropic endeavor that brings people together to enjoy the region’s wines while raising funds for the community.

“If visitor-ship trends do not fully return to pre-pandemic levels, we may see more on-the-road activations or marketing event participations,” noted Cain. “We may also see tasting experiences or tasting room openings in other locations.”

For Cakebread, that’s led to establishing a new tasting room, Mullan Road Cellars, in Woodinville, Washington. The wine project focuses on Bordeaux varieties and is slated to open its doors to tasting guests in late summer 2023.

A line-up of wines in the indoor tasting room at Tablas Creek near Paso Robles (photo by C. Merlo.)

Crown Point’s Fairbanks believes wineries of all sizes will continue to invest more money into their DTC experiences, whether by tasting room enhancements, digital outreach or direct-from-the-winery website purchases. Direct access to the proprietor or winemaker “will always resonate with consumers,” he said.

At Melville Winery, the biggest push in the tasting room will come from elevating visitor hospitality, with more employee training to achieve that. These days, Chad Melville said, too many consumers feel they’re paying more while getting less hospitality, whether they’re at a restaurant, hotel or entertainment venue.

“We’re not trying to be that,” said Melville. “We want to make sure our guests walk away and say, ‘That was an incredible experience.’”

Federal Definition Sought for Biostimulant Products in Agriculture

By
Cecilia Parsons | Associate Editor
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Biostimulant product use in California vineyards is increasing, according to UCCE Viticulture Advisor Joy Hollingsworth (photo by C. Parsons.)

Despite regulatory uncertainty, biostimulant product use in California vineyards is increasing, UCCE Viticulture Advisor Joy Hollingsworth confirms, but growers should be aware of product limitations and carefully read labels.

Match the product with what you want to achieve, said Hollingsworth.

She notes biostimulant products are not intended to be fertilizers though they may contain some nutrient compounds.

Hollingsworth said some biostimulant products could be viewed as an ‘assist’ to fertilizer. The products may contain 1% to 2% nitrogen but are not meant to be a replacement for fertilizer.

Biostimulants are biological products that are applied to plants or soil to achieve improved plant growth. Depending on the type of biostimulant, the products are intended to reduce plant stress or aid in nutrient uptake with increased soil microbe activity. Other claims of benefits achieved with biostimulant use, including carbon sequestration and improving water quality, would depend on timing of application, soil type or other environmental conditions.

As defined in the 2018 Farm Bill, “Biostimulants are a substance or microorganism that, when applied to seeds, plants or the rhizosphere, stimulate the natural processes to enhance or benefit nutrient uptake, nutrient efficiency, tolerance to abiotic stress or crop quality and yield.”

In 2019, an EPA report defined biostimulants in a similar way, but the definition also refers to soil health improvement as a potential benefit rather than crop quality or yield.

That left the products in a recognized but uncertain regulatory state, Keith Jones, executive director of Biological Products Industry Alliance, said. Without a federal definition, he said, they cannot be regulated or sold in the U.S.

Standardize Rules
In March 2023, a bill to standardize rules for plant biostimulants and promote research was introduced in the U.S. Senate. The Plant Biostimulant Act would create a uniform process for approving commercial plant biostimulant use as an alternative to synthetic pesticides and fertilizers according to U.S. Senators Alex Padilla and Mike Braun who introduced the bill.

They claim the use of plant biostimulant technologies has shown promise in sustainability management practices such as carbon sequestration and water quality improvement.

According to USDA and U.S. EPA, the plant biostimulant industry is expected to become a $5 billion global market by 2025, but the path to market for products in the U.S. remains inconsistent. The bill would implement a uniform federal definition and federal guidance from EPA and USDA. The senators noted the lack of standard regulatory definition makes accessing this technology difficult for the agriculture industry.

The act would amend the Federal Insecticide, Fungicide and Rodenticide Act (FIFRA) to establish a consistent national definition for the new agricultural product category of “plant biostimulant” and specifically exclude such products, which are not pesticides, from FIFRA regulation.

The goal of the recently introduced legislation to research and standardize rules for plant biostimulants is not about regulation; it is making the products available for use in crop production, Jones said.

“This bill, and a model bill that states can adopt, is a legitimate pathway to the market for these products,” Jones said.

The model bill, expected as early as 2024, is being written by American Association of Plant Food Control and can be adopted by individual states to allow sale of biostimulant products. Jones said presently in California, a biostimulant product can be modified with nutrient compounds to be registered for use in California as a ‘soil amendment.’ Microbial biostimulants can also be modified to have some pesticidal effect to be registered for use in crop production.

Biostimulant products for crop production generally fall into three categories: acids, including fulvic or humic; microbials, which can be fungi or rhizobium; and extracts or secondary metabolites like polyphenols or botanicals. In addition, there are other types of biostimulant products which do not fit in those three categories. Acid-based products can be applied as a foliar through irrigation systems or directly on the soil. Microbial products may need an incubation period prior to use. Extracts can also be foliar applications through irrigation or soil applied. They have been found to improve soil conditions for roots.

While more growers are using biostimulant products in vineyards, they should be aware that improvements in growth, grape quality or other benefits may not become apparent during the current growing seasons (photo courtesy Lodi Winegrowers Workbook 2nd Edition).

In grape production, most biostimulant product research has been aimed at foliar applications which have the potential for reacting more rapidly with the plant biological processes than if applied to the soil. Foliar-applied biostimulants that have shown benefits in grapes include chitosan, which improved postharvest grey mold infections as well as fungicides. There have also been studies showing improved anthocyanin concentrations in grapes with foliar seaweed applications. Biostimulant product research is ongoing, demonstrating increased interest in their use for plant and soil health.

Growers who use these products in vineyards should look carefully at the label to make sure it can do what is intended. For example, a biostimulant product that claims to improve water holding capacity will not provide much of a benefit in clay soils. Hollingsworth also noted that while more growers are using biostimulant products in vineyards, they should be aware that improvements in growth, grape quality or other benefits may not become apparent during the current growing seasons. In addition, biostimulant products are not intended to prevent pest damage or kill pests. They are also not intended to enhance natural growth behavior of the plant beyond what could be realized under optimal growing conditions.

Barriers to adoption of biostimulant use, according to The Fertilizer Institute, include lack of a clear and consistent definition, confusion about plant nutrient classification and lack of uniform regulatory framework which inhibits research.

Regulatory and Legislative Updates Affecting Vineyards and Wineries

By
Rebecca Scott | Attorney; Realtor, London Properties; Majority Partner, JWAGronomics, LLC
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Regulatory and Legislative Updates Affecting Vineyards and Wineries

Please note the following is not an exhaustive list of all relevant laws. For example, updates to COVID-19-related restrictions are not addressed, nor is any Federal law. In addition, the overview provided here does not include every aspect of each bill. This is intended as a highlight to red flag potential issues. For any area of concern, you are encouraged to reach out to local legal counsel.

SB 19 – Allowing 2nd Licensed Branch Premises for Tastings & Retail Sales – Effective 1/1/2022
The former law prohibited a winegrower or brandy manufacturer from selling wine or brandy to consumers, or engaging in winetasting activities, at more than one licensed branch premise. This bill revises the prohibition to allow a winegrower or brandy manufacturer to sell wine or brandy to consumers, or to engage in winetasting activities, at up to TWO licensed branch premises.

CA Business & Professions Code.

AB 239 – Consumer Provided Containers – Effective 1/1/2022
Under prior law, a winery could not, at its Duplicate Type 02 premises, sell or deliver wine to consumers in containers supplied, furnished, or sold by the consumer. AB 239 amends the Alcoholic Beverage Control Act to allow consumers to provide their own bottles and containers to be filled at a Duplicate Type 02 tasting room premises.

CA Business & Professions Code.

AB 1267 – Advertising Charitable Donations with Sale of Alcohol – Effective 1/1/2022
The Alcoholic Beverage Control Act prohibits a licensee from giving a premium, gift or free goods in connection with the sale and distribution of any alcoholic beverage, except as provided. The bill authorizes a winegrower, a beer manufacturer, a distilled spirits manufacturer, a craft distiller, a brandy manufacturer, a rectifier or a wine rectifier to donate a portion of the purchase price of an alcoholic beverage to a nonprofit charitable organization in connection with the sale or distribution of an alcohol beverage, subject to certain limitations.

Promotion or advertisement of the donation shall not directly encourage or reference the consumption of alcoholic beverages.

This carved out exception sunsets on Jan. 1, 2025.

CA Business & Professions Code.

SB 793 – Alcoholic Beverages & Music Venue Licenses – Effective 1/1/2023
This bill establishes a “music venue license,” to be issued by the Department of Alcoholic Beverage Control, to a music entertainment facility that may be open to all ages. The license will allow alcoholic beverage service to adults only, including beer, wine, and distilled spirits. The license allows consumption on the premises during the time period from two hours before a live performance at the venue until one hour after the live performance.

CA Business & Professions Code.

SB 1370 – Alcoholic Beverage Licenses – Specific to Nonprofit Radio Broadcasting Companies – Effective 1/1/2023
This bill makes nonprofit radio broadcasting companies eligible for a type 64 license, subject to the same licensing fees as nonprofit theater companies. Similar to nonprofit theater companies, a nonprofit radio broadcasting company is not considered a public premises and may sell alcoholic beverages to ticketholders only from two hours before until one hour after a bona fide performance, and the license is only for a single specified premises.

CA Business & Professions Code.

SB 3 (2016) Minimum Wage Increase – Incrementally Effective 1/1/2023
Due to the incremental enactment of SB 3(2016), the California minimum wage increased to $15.50 per hour, effective Jan. 1, 2023 for all employers.

This hourly wage increase adds businesses with 25 or fewer workers to the existing requirements for employers with more than 25 workers.

CA Labor Code.

SB 1162 – Pay Data Reporting & Transparency – Effective 1/1/2023
Re Any employer with 100 or more employees/100 or more labor contract employees. Employers must submit pay data reports to the CA Civil Rights Department within the Business, Consumer Services and Housing Agency on or before the second Wednesday of May 2023, and for each year thereafter on or before the second Wednesday of May. A separate report is required for each individual location.

The Bill requires the pay data reports to include the median and mean hourly rate for each combination of race, ethnicity and sex within each job category. This Bill deletes the provision authorizing an employer to submit an EEO-1 in lieu of a pay data report. The Bill also includes job posting transparency requirements for pay ranges and contains civil penalties for failure to comply.

CA Government Code; CA Labor Code.

AB 1041 – Family Leave – California Family Rights Act– Effective 1/1/2023
For employers of five or more employees, this Bill expands the class of people for whom an employee may take leave to care for to include a designated person, not necessarily related by blood, but by the equivalent of a family relationship. The bill would authorize an employer to limit an employee to one designated person per 12-month period.
The Bill also expands the definition of the term “family member” to include a designated person, which, for purposes of these provisions, would mean a person identified by the employee at the time the employee requests paid sick days, subject to limitation by the employer, as prescribed.

CA Government Code; CA Labor Code.

AB 1949 – Bereavement Leave – California Family Rights Act – Effective 1/1/2023
This Bill makes it an unlawful employment practice for an employer to refuse to grant a request by an eligible employee to take up to five days of bereavement leave upon the death of a family member, as defined. The bill would require that leave be completed within three months of the date of death. The bill would require that leave be taken pursuant to any existing bereavement leave policy of the employer. Under the bill, in the absence of an existing policy, bereavement leave may be unpaid.

For purposes of this Bill, “Employee” means a person employed by the employer for at least 30 days prior to the commencement of the leave and does not include civil service.

CA Government Code.

AB 1066(2016) – Overtime Pay for Agriculture Workers –Incrementally Effective 1/1/2023
In 2016, Assembly Bill 1066 created a timetable for agricultural workers to receive overtime pay so they will gradually receive overtime pay on the same basis as workers in most other industries (after eight hours per day or 40 hours per week.)

Starting Jan. 1, 2023, employers with 25 or fewer employees must pay agriculture workers overtime after 9 hours per day or 50 hours per week. Large employers with 26 or more employees since January 1, 2022, must pay agriculture workers overtime after 8 hours in a day or 40 hours in a week.

Additional increments go into effect 1/1/2024 and 1/1/2025.

CA Labor Code.

AB 2183 – Labor Peace Contracts for Ag Employees – Effective 1/1/2023
Existing law grants agricultural employees the right to form and join labor organizations and engage in collective bargaining with respect to wages, terms of employment and other employment conditions, and authorizes employees to elect exclusive bargaining representatives for these purposes.

This Bill refers to the election by secret ballot process as a polling place election. The bill establishes alternative procedures to the polling place election and authorize a labor organization to be certified as the exclusive bargaining representative of a bargaining unit through either a labor peace election or a non-labor peace election, as prescribed, dependent on whether an employer enrolls and agrees to a labor peace election for labor organization representation campaigns. The Bill establishes a schedule for agricultural employers to indicate to the board whether they agree to a labor peace compact.
This bill prescribes civil penalties to be imposed upon an agricultural employer who commits an unfair labor practice.

CA Labor Code.

SB 1013 – Beverage Container Recycling – Effective 1/1/2024
This bill amends the California Beverage Container Recycling and Litter Reduction Act (Bottle Bill). This bill requires a wine direct shipper permitholder, before sending any shipment to a resident of California, to register with the Department of Resources Recycling and Recovery as a beverage manufacturer and distributor under the California Beverage Container Recycling and Litter Reduction Act. The act requires a distributor to pay a redemption payment for every beverage container sold or offered for sale in the state to the Department of Resources Recycling and Recovery and requires the department to deposit those amounts in the California Beverage Container Recycling Fund. This amendment revises the definition of beverage to include distilled spirits and wine or wine from which alcohol has been removed in whole or in part, whether sparkling or carbonated.
Wine direct shipper permitholders are required to register with CalRecycle as a beverage manufacturer and to comply with the Bottle Bill, including the reporting and payment provisions applicable to the permitholder as a beverage manufacturer and distributor. Failure to comply may result in suspension or revocation of the shipper permit.

A violation of the act is a crime.

Additional labeling requirements go into effect in 2025.

CA Business & Professions Code; CA Public Resources Code.

Micro-Winery Ordinance Specific to Napa County Only – Effective 5/5/2022
The Ordinance streamlines the use permit application process to allow family farm winegrape growers to produce and sell wine at their farms. The application is processed by the zoning administrator, rather than going through the more formal process with the planning commission.

This process is only available to micro-wineries fermenting on-site at least 201 gallons of wine annually but having a capacity for no more than 5,000 gallons annually. Subject wineries must be on parcels of at least 10 acres, and within the Ag Preserve and the Ag Watershed zones. Facilities must be no more than 5,000 square feet, including storage, processing facilities, tasting areas and caves. At least 75% of the grapes used in fermentation on-site are grown on the same property as the micro-winery or contiguous parcels under the same ownership. No more than 20 Average Daily Trips are generated by visitors, employees or deliveries. Tours, tastings and retail sales may be conducted on-site, but only between the hours of 9 a.m. and 6 p.m.

Once micro-winery use permit is approved, no additional or expanded permit will be considered for a two-year period post-approval.

The Ordinance sunsets in May 2025, at which time Napa County will re-evaluate the process.

Napa County Code of Ordinances

References
abc.ca.gov
calcivilrights.ca.gov/family-medical-pregnancy-leave/
dds.ca.gov/rc/vendor-provider/minimum-wage/
dir.ca.gov/
leginfo.legislature.ca.gov/
Botting, M., “California Tied-House Laws.” https://www.californiacraftbeer.com/wp-content/uploads/2016/09/ABC-Tied-House-Law.pdf
Corrigan, J. “7 California Employment Law Changes in 2023.” January 3, 2023. https://www.hcamag.com/us/specialization/employment-law/7-california-employment-law-changes-in-2023/431662
Gardner, D., Bollag, S., “Here are 13 new laws Californians must start following in 2023.” December 5, 2022. https://www.sfchronicle.com/politics/article/new-california-laws-2023-17626931.php
Auerbach Allderdice, L., Haney, J.H., Hill, T.E., Polk, L.N., Stone, S.J, Tellado, T, Vu, M.T., Sahachartsiri, B., “New California Labor & Employment Laws for 2023.” December 29, 2022. Holland & Knight Alert. https://www.hklaw.com/en/insights/publications/2022/12/new-california-labor-and-employment-laws-for-2023
McGuire Woods. “New California Employment Laws Take Effect in 2023.” January 4, 2023. https://www.mcguirewoods.com/client-resources/Alerts/2023/1/new-california-employment-laws-take-effect-in-2023
Neish, S., “New Napa Law Gives Micro-Wineries a Fighting Chance.” June 29, 2022. https://www.thedrinksbusiness.com/2022/06/new-napa-law-gives-micro-wineries-a-fighting-chance/
Tilley-Coulson, E., “California Leave Law Updates.” February 2023. https://www.lockelord.com/newsandevents/publications/2023/02/california-leave-law-updates2023#:~:text=The%20second%20new%20law%2C%20also,months%20of%20a%20qualifying%20death.
Trindad, J., Hobel, B., Mercurio, M., “New Laws Expand Winery Off-Site Tasting Room Privileges and Manufacturer Charitable Donation Advertising.” September 24, 2021. https://www.dpf-law.com/blogs/lex-vini/new-laws-expand-winery-off-site-tasting-room-privileges-and-manufacturer-charitable-donation-advertising/

Raging Bull Vineyards and Winery: A Unique Blend from the Roots Up Orland Couple Learns the Trade from Scratch to Success

By
Julie R. Johnson | Contributing Writer
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Raging Bull Vineyards and Winery produces award-winning wines at the vineyard, tasting room and winery in Orland, Calif. (photo courtesy Raging Bull Vineyards and Winery.)

It’s one of only two of its kind nestled in the rolling foothills of Northern Sacramento Valley’s Glenn County. Raging Bull Vineyard and Winery is the home of Charlie Sullivan and Sharon Shipley, who in partnership with Winemaker Bryan Shaw produce grapes and wines from 20 acres of vineyards against a backdrop of the magnificent Mendocino Mountain Range.

Unlike most vineyards and wineries in the Northstate that have a view of the Mendocino range looking eastward, Raging Bull’s view is unique in that it is looking westward to jagged peaks that on any given evening can silhouette a burning sunset catching the clouds on fire.

90 minutes north of Sacramento and a few miles off Interstate 5, Raging Bull offers peace and quiet with nothing else around except a few mooing bovines grazing the grassy knolls.
“Raging Bull Vineyards and Winery is a small, boutique winery,” Shipley says. “Along with our wonderful wines, it’s the perfect spot for your wedding, reunion, anniversary party or just a get-together with friends.”

She is adamant that Sullivan is the mover and she’s the shaker behind Raging Bull, and together the two can make grapes and wine happen.

Raging Bull’s website states, “What started as a blank-canvas land purchase by Charlie has been morphed by their vision and efforts into what it is today.”

However, while it is Sullivan who owns everything, it is Shipley who puts the fine points and details to Raging Bull’s success.

Her contributions are obvious everywhere you go, from the decorations and stone fire-pit to the custom half-tables in the bar, all done by Shipley, whose previous career was in human resources for 16 years at a copper mine before moving to Northern California. She can be found engaging in all aspects of the winery, from watering, to picking, to crushing.

Standing in front of Raging Bull Vineyards and Winery’s 1900 antique wood-carved bar that lends its tasting room a unique, one-of-a-kind atmosphere, is the owner of the Glenn County business, Charlie Sullivan (photo by J.R. Johnson.)

Origins
A few years ago, about 2016, Shipley said, “Charlie decided what we could grow out here west of Orland to have a little extra spending money for retirement.”

A retired well-driller, previous owner of Sullivan Drilling in the Northstate, Sullivan decided to grow grapes to sell to other vineyards.

“And because of numerous other reasons,” Shipley added. “But the main one is that grapes don’t take a lot of water.”

The couple worked the first five acres of the vineyard, and by the end of that summer, they had about five acres of vines planted.

“We sure didn’t know a lot about growing grapes and we had to learn mighty fast,” Shipley said. “Thanks to many friends and lots of advice and reading on how to train, water, grow and whatever else we needed to get this crop growing, we got it done.”

A couple years after that first summer’s planting, Sullivan and Shipley had produced their first crop and had to find a way to get them harvested.

“So, we read on how to do that and gathered up all the help we could and got the first harvest completed, that was 2019, we harvested the crop, fermented them and made a 2019 blend wine,” Shipley said.

It is the fine points and details at Raging Bull Vineyards and Winery that can be attributed to Sharon Shipley, pictured, whose contributions are obvious everywhere at the facility, from the decorations and stone fire-pit to the custom half-tables in the bar (photo courtesy Raging Bull Vineyards and Winery.)

Not too long after, the couple hired a winemaker, Shaw.

“He told us, ‘Well, you didn’t ruin the wine,’ and we looked at ourselves and said, ‘Really?’” Shipley added.

“Well, as of today, that blended red wine is our No. 1 selling wine, and it just keeps getting better and better.”

The couple agree they have come a very long way and know much more than they ever thought they would.

“And we just keep learning about something we love to know and learn more about,” Shipley said.

Raging Bull Vineyards and Winery is located in Glenn County a few miles west of Interstate 5 and is surrounded by rolling, grassy hills with a backdrop of the Mendocino Mountain Range (photo by J.R. Johnson.)

The operation sits on rolling, grassy hills, speckled with old oaks. The tasting room and winery sit next to a large, fish- and croc-infested (fake of course, I hope) pond where guests can paddle around in canoes. The tasting room extends into an outdoor gazebo overlooking the pond with a view of the vineyard and mountain range.

Inside the 4,560-square-foot barn that houses the tasting room and winery heralds a beautiful carved wood 1900 antique bar that came from Sacramento. The ornate bar is what gives the room its unique atmosphere along with the Texas longhorns mounted above.

Winemaker Bryan Shaw started with Raging Bull in June 2021. He was educated in the viticulture and enology winemaking program at UC Davis and has won multiple silver and gold medal awards for his past vintages of wines at previous wineries (photo by J.R. Johnson.)

“One of only a handful remaining, it’s a beautiful piece of turn-of-the-century craftsmanship unseen in modern building,” Sullivan said.

“This is a perfect place for having a seat and sampling the end result of the production happening all around you,” Shipley said.

With the grapes sitting at the front of the property, Raging Bull boasts an additional 200 acres of land, great for stretching legs, running your dogs, enjoying wildlife and getting a first-hand, up-close view of the vineyard.

Built in 2019, the barn and extended pad behind it serve as most of the grape processing, fermenting and racking space. Two office spaces are on one side and on the other are dual ADA-compliant, four-stall bathrooms. The winery also has three ADA-compliant shower stalls with tiled walls and pebbled floors.

Unique Setting
“We chose to grow grapes in our climate because it is a very consistent climate that is dry,” Shipley said. “The vines tolerate the heat, volcanic rock soil with hillside drainage, and we have plenty of water.”

Sullivan says the uniqueness of the vineyard is that everything is grown and bottled onsite whereas many wineries nowadays either buy their grapes or wine from other wineries that specifically sell and grow the grapes.

“We are also a vineyard that offers guests to come out and watch our process, help if they choose, watch us bottle or harvest, take a tour around the vineyard in our eight-man golf cart and try the grapes that our wines are made from,” Shipley added.

There is only one other winery in Glenn County, and it sets on the east side of the valley.

Wines and Winemaker
“Prefer certain varietals of wine? This vineyard is sure to have something to your tastes,” Sullivan said. Currently planted are Cabernet, Malbec, Syrah, Sauvignon Blanc, Merlot and Grenache Noir.

“When we have guests, we love to tell the story of how we started this and how our wines have evolved to award-winning wines that have even been featured in Sunset Magazine, The Critics Challenge in San Diego and the San Joaquin Valley Wine Challenge,” Shipley said.

The vineyard and winery feature some of the finest equipment for an operation the size of Raging Bull.

“Our wines are made in the mind of old school technology with the most modern equipment,” Sullivan said. “We use the finest yeast and plant-based additives to make the wines and varieties our customers are sure to enjoy.”

Providing water to the vineyard are two 16-inch agriculture wells along with two domestic wells. All four were drilled by Sullivan, who has been drilling water wells for nearly 40 years.

Winemaker Bryan Shaw started with Raging Bull in June 2021.

He was educated in the viticulture and enology winemaking program at UC Davis and has won multiple silver and gold medal awards for his past vintages of wines at previous wineries.

His knowledge in many winemaking styles and fermentation techniques have been incremental to Raging Bull.

“We chose Bryan Shaw, our winemaker, because he has a variety of expertise, knowledge and education that simply makes a good wine,” Shipley said.

Shaw has worked along some of the best winemakers in the country and is very thorough and focused on how to make an award-winning wine, Sullivan added.

“He loves to chat with the customers and entice them with his knowledge on winemaking and will even go so far as to do barrel tasting with them,” Shipley says.

Sullivan adds that the process of winemaking is up to the winemaker and what he wants to achieve with the grapes.

“We use stainless steel tanks and numerous kinds of oak barrels in our processing,” he said. “We go through a fermenting, destemming and crushing process before the wines get into the barrels and tanks.”

The winery bottles twice a year by appointment with a mobile wine-bottling service as is customary these days.

To date, the winery’s award-winning wines are Syrah, earning three gold medals, 2020 Cabernet Sauvignon with three silver medals and 2020 Merlot with one bronze.

New Approach to Ant Control in Vineyards Hydrogel Applications May Become an Option for Growers

By
Cecilia Parsons | Associate Editor
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Sugar-feeding ants are the monkey wrench in a vine mealybug integrated pest management program (all photos courtesy D. Haviland.)

Sugar-feeding ants are the monkey wrench in a vine mealybug (VMB) integrated pest management program.

Not only does their feeding on honeydew secreted by VMB promote sooty mold on grape clusters, ants know their next meal depends on VMB and actively protect this invasive pest from predator insects and parasitoids that provide biological control and are part of a vineyard integrated pest management program.

Vine mealybugs feed by sucking plant juices. They excrete honeydew which attracts sugar-feeding ants. Since the introduction and spread of VMB in California vineyards, the presence of sugar feeding ants in vineyards has become a much larger issue. Chemical and biological IPM strategies can work in controlling vine mealybug, but when sugar-feeding ants are present, biological control efficacy is impacted.

David Haviland, UCCE entomologist in Kern County, said sugar-feeding ants interrupt VMB control measures, protecting this invasive grapevine pest by killing or intimidating VMB predators and parasitoids that exist in the vineyard. Chemical controls for VMB are a challenge as this mealybug species has numerous life stages that can be present at the same time. Adults or nymphs or eggs may be killed, but unaffected stages re-populate grapevines. Ants can also help VMB survive by moving them under bark to escape contact insecticides.

Hydrogels have potential to control sugar-feeding ants in vineyards as the solution requires a fraction of chemical pesticide use compared to foliar applications.

Presence of sugar-feeding ants in a vineyard minimizes impact of an integrated pest management plan, Haviland confirmed.

There are different species of ants that cause the same problem for VMB control throughout all grape growing regions of California.

The sugar-feeding invasive Argentine ant is the most prevalent ant species in coastal vineyards. It is about 3 millimeters in length, is uniformly deep brown to black and does not bite or sting. It has one hump between the thorax and abdomen. Worker ants forage during the day. Their populations peak in mid-summer and early fall. Ants nest usually within 2 inches of the soil surface.

In the San Joaquin and Coachella valleys, sugar-feeding native gray ants are most prevalent. These ants are 7.5 millimeters in length and, like the Argentine ant, have one hump. Gray ants nest in the topsoil or under rocks or vineyard debris. They move in an irregular, jerky motion and generally do not travel along trails or sting. Different sub species are found in the San Joaquin and Coachella Valley. The thief ant is the smallest sugar-feeding species and is found primarily in the Coachella Valley.

Other ant species may be found in vineyards, but they are primarily protein feeders.

Control Has Become Harder
Haviland said control of ants in vineyards has become problematic due to loss of the effective chlorpyrifos and increased demand by markets for use of sustainable farming practices. Integrated pest management fills that need, but without ant control is less effective.

Prior to the loss of the organophosphate insecticide Lorsban, it could be used to knock back ant populations in vineyards, Haviland said. An added emphasis on biological control methods in grape production has led growers to encourage native predator populations or to purchase parasitoids to distribute in vineyards.

David Haviland, UCCE entomologist in Kern County, said sugar-feeding ants interrupt vine mealybug control measures, protecting this invasive grapevine pest by killing or intimidating vine mealybug predators and parasitoids that exist in the vineyard.

To preserve the viability of these biological controls, a search began for innovative ant control measures.

Haviland, who spoke about innovations in ant control at the Southern San Joaquin Valley Grape Symposium, said the granular ant baits are more attractive to protein feeding ant species and fail to cut into sugar-feeding ant populations.

Varying environmental conditions in all California grape growing regions also pose difficulty for ant control measures. Liquid baits placed in bait stations are used in vineyards but have not been widely adopted, Haviland said, due to costs. The number of stations needed to be effective and the labor required to maintain them are challenges. High summer temperatures also cause the water portion of the bait to evaporate, and the concentrated bait left is no longer attractive to ants, compared to their diet of VMB honeydew.

Hydrogel Bait as a New Solution
In exploring other options for ant bait delivery, Haviland turned to hydrogels.
There is no shortage of hydrogel definitions in scientific publications, but the easiest to understand is that a hydrogel is mostly a mixture of porous, permeable solids at least 10% by weight or volume of interstitial fluid composed completely or mainly by water. Hydrogels have three-dimensional network structures which can absorb relatively large amounts of fluid (think diapers).

Haviland said sucrose absorbed by hydrogels makes “artificial honeydew.” Very small amounts of pesticide are added to the mix for ant control.

“The amount needed is 100 times lower than is used on foliage for pest control,” Haviland said. The concentration of pesticide is one-tenth of normal use of product. Trials have done applications at rates of 10 gallons of hydrogels per acre, and in some trials, it was effective at 5 gallons per acre.

There are a lot of different types of hydrogels, and Haviland said UC Riverside Entomologist Mark Hoddle’s research found polyacrylamide gels, which have a high level of degradability, are suited for carrying a pesticide mixture.

After hydrogels absorb the sucrose and pesticide mixture, they can be broadcast across a vineyard floor with a broadcast spreader. Haviland explained ants are attracted to this sugar source with a ‘Jello’ consistency that is wet on the outside.

This bait delivery system is experimental, Haviland stressed, but is showing promise in field trials. There is also an example of use of hydrogels to successfully eradicate Argentine ants. At Channel Islands National Park, Argentine ants were threatening populations of native birds. Hydrogel baits were used, and over time, ants were eradicated from Channel Islands.

Haviland said this technology is currently not registered for use as hydrogel delivery is not on any insecticide label. The process to supplement current insecticide labels for use in hydrogel delivery has started, he said. This would involve a 24-C petition to use a pesticide in a different manner than what is noted on the label.

When this ant bait delivery system is approved, Haviland said the window to apply in San Joaquin Valley vineyards would be March 15 to May 1. Honeydew isn’t being produced in large quantities before May, he said. The expected program would be two applications of hydrogels a month apart in valley locations. Timing would be adjusted for coastal or desert areas.

The Increasing Importance of CAWG in an Ever-Changing Industry and Political Landscape

By
Natalie Collins | President, California Association of Winegrape Growers
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The California Association of Winegrape Growers represent the collective voice of growers at the state, federal and regulatory levels to advocate for policies and practices that support the sustainability and growth of the winegrape industry.

California is home to some of the most sought-after vineyards in the world, and for good reason. The combination of our unique climate, diverse geography and experienced growers makes it possible to produce world-class grapes that go into exceptional wines.
While the fickle whims of the weather continue to cause challenges, grape growers must also navigate the equally unpredictable terrain of the political climate, where policies and regulations can make or break their livelihoods.

Natural phenomena such as weather events are beyond our control, but the political climate can certainly be influenced through actions and advocacy. With this in mind, the California Association of Winegrape Growers (CAWG) was established in 1974 with the mission to promote the interests of California winegrape growers, giving them a unified voice in the policy-making process. Almost 50 years later, CAWG continues to represent the collective voice of growers at the state, federal and regulatory levels to advocate for policies and practices that support the sustainability and growth of the winegrape industry.

From Passion to Presidency
Growing up surrounded by the vibrant agricultural landscape of the San Joaquin Valley sparked my passion for the industry. Active involvement in organizations like 4-H and FFA further fueled my enthusiasm, leading me to pursue a degree in agricultural business from California State University, Chico and launch a career in agriculture.

In 2015, I joined CAWG as the director of member relations, leading our grower outreach, education and membership efforts. Following a brief period as interim president, I was officially appointed as president of the association in late 2022. I am thrilled to carry on the legacy of robust leadership, working collaboratively with our 27 elected grower board members and exceptional staff. With this shared dedication, CAWG will continue to serve as a powerful advocate for California winegrape growers.

State Sponsored Legislation
The year has kicked off with a flurry of activity as we delve into both state and federal matters. Lawmakers have introduced more than 2,600 bills this year, the highest number in over a decade. While we will take a stance on several bills that affect growers, we are also sponsoring and co-sponsoring the following legislation.

SB 659 – Groundwater Recharge
CAWG is sponsoring SB 659 (Ashby, D-Sacramento). The intent of this bill is to create the statutory framework and a statewide focus on the most impactful solution to address the water management challenges presented by climate change in California.

Unless there is a substantial shift in the approach to water supply, California’s water resources will eventually be depleted. This is an undeniable fact. According to Governor Newsom’s Water Supply Strategy released in August 2022, California is projected to lose around 7.5 million acre-feet annually by 2040. However, it is worth clarifying that California is not running out of water. Recent storms have demonstrated the immense potential of collecting stormwater for groundwater replenishment. This indicates that we must adopt a new paradigm for water management. This is a critical juncture that necessitates prompt action.

Following a brief period as interim president, Natalie Collins was officially appointed as president of the California Association of Winegrape Growers in late 2022 (all photos courtesy N. Collins.)

By creating a goal of 10 million acre-feet of new groundwater annually by 2035, SB 659 moves past the promise of a strategy, and we can begin the real work on groundwater recharge projects that are shovel-ready. By placing this requirement in law, that statutory goal would need to be a consideration in rulemaking and funding decisions by all state agencies having authority over water.

AB 54 – Research Funding: Winegrape and Smoke Exposure
With the unprecedented losses growers and wineries suffered in 2020 due to wildfire smoke, CAWG and Wine Institute are co-sponsoring AB 54 (Aguiar-Curry, D-Winters). Under this bill, the California Department of Food and Agriculture (CDFA) would allocate funds toward smoke research. These research dollars would facilitate efforts to explore precise way of measuring smoke compounds, methods to mitigate the damage that can occur from exposure to smoke, and methods to prevent smoke damage to winegrapes and wine.

AB 54 would also require CDFA to establish an advisory committee of specified members to provide recommendations for funding research proposals submitted to the department under these provisions. The bill asks the legislature to set aside $5 million in the state budget for this research.

SB 375 – COVID-19 Tax Credit
CAWG is sponsoring SB 375 (Alvarado-Gil, D-Jackson) to provide employers with financial relief from the cost of compliance with the new COVID-19 workplace safety standards that took effect on February 4.

SB 375 would provide an annual credit against state payroll taxes to reimburse employers for costs such as testing, masking, ventilation systems, exclusion from work and other pandemic-based regulatory compliance costs.

CAWG and our members appreciate the commonsense leadership displayed by Senator Alvarado-Gil in authoring this much-needed legislation. SB 375 will support California employers and growers throughout the state who are still recovering from the pandemic and alleviate the burden put onto employers for a community-spread virus.

Autonomous Agricultural Equipment
CAWG is leading the push toward amending California regulations to allow for the full utilization of self-driving tractors, robotics and other autonomous farm equipment. This involves industry partners from all aspects of agriculture, academia and manufacturers. Our goal is to increase awareness of the advantages of precision viticulture for the environment, workforce and growers, and to apply that information and science to cleaning up California law which is based on technology developed 80 years go. That law severely restricts the full utilization of that equipment.

2023 Farm Bill Priorities
The Farm Bill is a comprehensive piece of federal legislation passed every five years by Congress. It covers a wide range of agricultural and rural development policies, including crop insurance, commodity programs, conservation, nutrition assistance, research and development, and rural development programs.

CAWG’s priorities in the 2023 Farm Bill include:
Mechanization and Automation Research: CAWG is advocating for the strengthening of research provisions geared towards new technologies, equipment and systems that alleviate concerns with labor availability and vineyard access.

Crop Insurance and Disaster Assistance: The 2020 wildfires dealt a severe blow to growers, underscoring the crucial role of crop insurance. Although there is room for improvement in the program, it remains an essential safeguard against devastating financial losses. CAWG is committed to advocating for ongoing enhancements to the Federal crop insurance program while promoting disaster relief programs.

Pest and Disease Investment: Our growers appreciate the level of support and attention given to the Animal and Plant Health Inspection Service and pest and disease efforts in the previous Farm Bill. The allocated funds have been effective in addressing several critical issues that, without such support, could have had devastating consequences. Going forward, CAWG strongly advocates for continued emphasis on research and development, tools and strategic measures to protect the agricultural industry from invasive pests and diseases.

Wildfire Smoke Research: And finally, there are always new research priorities that arise. It is crucial for the Farm Bill research title to provide access to funding for the industry to address emerging issues like the impact of wildfire smoke on winegrapes.

CAWG plays a critical role in the success and sustainability of the winegrape industry in California. Through advocacy and education, CAWG helps to ensure that winegrape growers have the support they need to thrive in an ever-changing industry and political climate.
The strength of the association lies in the support it receives from growers and industry partners. Joining CAWG can help you stay informed, connected, and competitive in the dynamic and rapidly changing California winegrape industry. If you are a grower or industry provider looking to improve your business, expand your network, and stay up to date on the latest industry trends, joining CAWG is a wise business investment.

Spatial Roguing: A Novel Leafroll Disease Management Response

By
Marc Fuchs | School of Integrative Plant Science, Cornell University
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Fruits of a healthy ‘Cabernet franc’ vine (all photos courtesy M. Fuchs.)

Leafroll is the most widespread and devastating viral disease of grapevine worldwide. It reduces yield, delays fruit ripening, increases titratable acidity, lowers sugar content in fruit juices, modifies aromatic profiles of wines and shortens the productive lifespan of vineyards. The economic cost of leafroll is estimated to range from $12,000 to $92,000 per acre of ‘Cabernet Sauvignon’ in California (Ricketts et al. 2015).

Grapevine leafroll-associated virus 3 (GLRaV 3) is the most dominant virus in leafroll-diseased vineyards. This virus is phloem-limited and transmitted by vegetative propagation and grafting as well as by several species of mealybugs. Mealybugs are sap-sucking insects and pests of grapes. At high densities, mealybugs can cause complete crop losses, rejection of fruit loads at wineries and death of spurs, although small infestations may not inflict significant direct damage. Several mealybug species feed on grapevines in California vineyards, including vine mealybug (Planococcus ficus), grape mealybug (Pseudococcus maritimus), obscure mealybug (Pseudococcus viburni) and longtailed mealybug (Pseudococcus longispinus) (Daane et al. 2012). Vine mealybug is an invasive species and the most damaging of the mealybugs that occur in California vineyards. Unassisted, mealybugs have limited mobility, but immature instars (crawlers) can be dispersed over long distances by wind and other means.

GLRaV-3 is acquired within one hour or less when instar mealybugs feed on infected grapevines. The virus is transmitted in a similar short time to healthy grapevines (Tsai et al. 2008). Following inoculation of healthy grapevines, it takes at least three months for GLRaV-3 to be detected in inoculated grapevines using laboratory-based diagnostic assays and one year for inoculated vines to exhibit typical leafroll disease symptoms in the vineyard (Blaisdell et al. 2016). In most diseased vineyards, the dynamics of leafroll spread is influenced by virus incidence and mealybug population density (Arnold et al. 2017, Cooper et al. 2018). In addition, the two adjacent vines to an infected vine are more likely to become infected over time than their counterparts located across the row, suggesting a predominant within-row virus spread and a spatial dependence for secondary spread (Bell et al. 2018).

Current Management Options
There is no cure for leafroll in diseased vineyards. However, the disease can be managed by reducing the number of infected vines and by controlling mealybug vector populations. For example, the elimination of diseased vines (a strategy known as roguing) and their replacement with clean vines derived from virus-tested nursery stocks that test negative for economically relevant viruses, including leafroll-associated viruses, reduce the incidence of GLRaV-3 and limit its secondary spread in vineyards (Bell et al. 2018, MacDonald et al. 2021).

Fruits of a ‘Cabernet franc’ vine infected with GLRaV-3.

Spatial Roguing, a New Response to Leafroll
Modelling leafroll disease spread in relation to economic factors predicted when roguing diseased vines, if disease prevalence is less than 25% (Ricketts et al. 2015) and two immediate within-row neighboring vines on each side, regardless of their disease status (for a total of five vines in the case of one infected vine), a strategy referred to as spatial roguing is more effective at reducing the level of virus inoculum in a diseased vineyard than roguing only diseased vines (Atallah et al. 2015). This strategy was inspired by the fact that 1) mealybug crawlers are more efficient vectors of leafroll viruses than adults; 2) crawlers are more likely to move along rows than between rows; 3) leafroll spread predominantly occurs at a short spatial scale; 4) a healthy-looking vine that is adjacent to a diseased vine may be infected without exhibiting disease symptoms; and 5) disease symptoms are only apparent at least one year after inoculation by viruliferous mealybugs (Blaisdell et al. 2016). Predictive models suggested that spatial roguing targeting symptomatic vines and their four immediate neighbor vines, two on each side, would be of statistically significant greater economic value than spatial roguing targeting symptomatic vines and their two immediate neighbor vines, one on each side. Simulations further predicted that a nonspatial strategy targeting only diseased vines is less effective and more costly than spatial roguing (Atallah et al. 2015).

We applied spatial roguing in a ‘Cabernet franc’ vineyard with overall low leafroll virus prevalence (5%) and a low grape mealybug population density in New York and tested its effectiveness at reducing the incidence of leafroll disease and slowing virus spread (Hesler et al. 2022). Four treatments were applied to select vine panels from 2016 to 2021: (1) spatial roguing only, (2) spatial roguing in combination with insecticide applications targeting grape mealybugs, (3) insecticide applications only (no spatial roguing), and (4) no spatial roguing and no insecticide intervention (the untreated control). Results showed that virus incidence was reduced from 5% in 2016 to less than 1% in 2020 to 2021 in both spatial roguing treatments. Among vines in the insecticide-free, non-rogued control treatment, virus incidence increased from 5 to 16% from 2016 to 2021 (Hesler et al. 2022). Insecticides applied in 2016 to 2021 helped significantly reduce grape mealybug populations to near zero annually, while populations in the untreated control vines were 57- to 257-fold higher during the same period (Hesler et al. 2022). This work validated spatial roguing as a leafroll disease management response in a vineyard with low disease incidence and low grape mealybug abundance.

A pair of grape mealybugs on the trunk of a ‘Cabernet franc’ vine.

Spatial roguing adds to the overall cost of vineyard maintenance. Revenue losses directly related to spatial roguing were estimated in our study at $5,565 per acre over six years (Hesler et al. 2022). These estimates agreed with earlier predictions and underscored the economic value of spatial roguing, despite added costs relative to the costs of maintaining a healthy vineyard, particularly when considering a scenario of no intervention, for which $10,000 to $15,750 losses per acre were calculated over a 25-year lifespan of a ‘Cabernet franc’ vineyard in New York (Atallah et al. 2012). The cost/benefit analysis of roguing may need to be evaluated by individual vineyard owners who are willing to adopt this leafroll disease management strategy. Critical to the success of roguing is the health status of the replants. Replants should be sourced from nursery vine stocks (scions and rootstocks) that have been extensively tested for viruses, including leafroll viruses, and shown to be clean (Bolton 2020).

In the future, it would be interesting to test the effectiveness of spatial roguing in California vineyards where mealybug population densities are consistently higher than in New York vineyards. Similarly, it would be interesting to compare the efficacy of spatial and nonspatial roguing approaches as a response to leafroll disease management. Of equal interest would be a study to test whether a sequential roguing strategy based first, for instance, on spatial roguing to drastically reduce sources of virus inoculum, and then on nonspatial roguing to limit secondary spread would be of value. If carried out in different vineyards with distinct disease prevalence, rate of spread and mealybug species and abundance, such research would inform the best approach for leafroll disease management both from a biological and economical perspective.

A six-year experiment in a commercial ‘Cabernet franc’ vineyard with low disease prevalence and low-density grape mealybug populations in New York showed that spatial roguing and the combination of spatial roguing and insecticides significantly reduced the percentage of infected vines. By comparison, virus incidence among vines in the untreated control vine panels where roguing was not implemented and no insecticides were applied increased from 5% to 16% during the same period. This study was the first to demonstrate the effectiveness of spatial roguing at reducing the incidence of leafroll disease and limiting its spread. It will be interesting to see whether our results on spatial roguing are reproducible in other vineyards of New York, and in vineyards of other grape growing regions of the world, including in California, where many more mealybug species, including the vine mealybug, are of concern and reside at higher populations.

References
Arnold K, Golino DA and McRoberts N. 2017. A synoptic analysis of the temporal and spatial aspects of grapevine leafroll disease in a historic Napa vineyard and experimental vine blocks. Plant Dis 107:418-426.
Atallah S, Gómez M, Fuchs M and Martinson T. 2012. Economic impact of grapevine leafroll disease on Vitis vinifera cv. Cabernet franc in Finger Lakes vineyards of New York. Am J Enol Vitic 63:73-79.
Atallah S, Gómez M, Conrad JM and Nyrop JP. 2015. A plant-level, spatial, bioeconomic model pf plant disease diffusion and control: grapevine leafroll disease. Am J Agri Econ 97:199-218.
Bell VA, Hedderley DI, Pietersen G and Lester PJ. 2018. Vineyard-wide control of grapevine leafroll-associated virus 3 requires an integrated response. J Plant Pathol 100:399-408.
Blaisdell GK, Cooper ML, Kuhn EJ, Taylor KA, Daane KM and Almeida RPP. 2016. Disease progression of vector-mediated Grapevine leafroll-associated virus 3 infection of mature plants under commercial vineyard conditions. Eur J Plant Pathol 146-105-116.
Bolton SL. 2020. What every winegrower should know: viruses. Lodi Winegrape Commission. pp. 138.
Cooper ML, Daugherty MP, Jeske DR, Almeida RPP and Daane KM. 2018. Incidence of grapevine leafroll disease: effects of grape mealybug abundance and pathogen supply. J Econ Ent 111:1542-1550.
Daane KM, Almeida RPP, Bell VA, Walker JTS, Botton M, Falladzadeh M, Mani M, Miano JL, Sforza R, Walton WM and Zaviezo T. 2012. Biology and management of mealybugs in vineyards. In Arthropod Management in Vineyards: Pests, Approaches, and Future Directions, N.J. Bostanian, ed. (Springer), pp. 271-307.
Hesler S, Cox R, Loeb G, Bhandari R, Martinson T and Fuchs, M. 2022. Spatial roguing reduces the incidence of leafroll disease and curtails its spread in a ‘Cabernet franc’ vineyard in the Finger Lakes region of New York. Am J Enol Vit 73:227-236.
MacDonald, SL, Schartel TE and Cooper ML. 2021. Exploring grower-sourced data to understand spatiotemporal trends in the occurrence of a vector, Pseudodoccus maritimus (Hemiptera: Pseudococcidae) and improve grapevine leafroll disease management. J
Ricketts KD, Gómez MI, Atallah SS, Fuchs MF, Martinson T, Smith RJ, Verdegaal PS, Cooper ML, Bettiga LJ and Battany MC. 2015. Reducing the economic impact of grapevine leafroll disease in California: identifying optimal management practices. Am J Enol Vit 66:138-147.
Tsai C-T, Chau J, Fernandez L, Bosco D, Daane KM and Almeida RPP. 2008. Transmission of grapevine leafroll-associated virus 3 by the vine mealybug (Planococcus ficus). Phytopathol 98:1093-1098.

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