For the first time many growers are facing the dilemma of what to do with fruit that will not be sold. Although wine inventories have been slowly building over the past few years, 2019 is the first year in which a number of growers are feeling the effects of excess supply due to the large 2018 crop.
Given that yields thus far for most growers have been “average” or better and there is significant unsold inventory of bulk wines, custom crushing uncontracted grapes in 2019 may not be a viable option. Hopefully there will be buyers as the harvest continues but in this market, the prices offered are likely to be less than the cost of production.
Allowing unsold fruit to remain on the vines may seem unthinkable yet with no income from those blocks, it makes sense. This means not dropping clusters by hand and not running a harvester in the vineyard to get the berries off.
From the perspective of a plant pathologist:
clusters that decompose over the winter - either on the vine or on the ground -
are not likely to have a noticeable effect on fungal disease pressure the following year given common vineyard floor management practices.
All common grapevine fungal pathogens exist inside vineyards. For example, fallen petioles, rachises that remain on the vine after mechanical harvest, pruning debris and woody tendrils that cling to trellis wires all support the growth of fungi. These fungi act as sources of inoculum that can infect wounds caused by pruning and suckering, and infect berries at bloom and other green tissue.
The fungi that colonize decaying berries include the same fungi seen growing on damaged berries before harvest including Botrytis cinerea and Cladosporium and Aspergillus species which are associated with Botrytis bunch rot, Cladosporium rot and sour rot respectively. Fungi can infect then colonize the ripening berries when spores enter through the slightest opening in the berry cuticle caused by sunburn or the presence of diffuse, unseen powdery mildew. Berries are an overwintering structures for these fungi and others.
Botrytis cinerea spores are ubiquitous given the fungus can survive on dead tissue as well as infect living tissue. It grows on dead calyptras (flower caps) and stamens after bloom and will infect a young berry through the wounds left when the cap is shed. In various studies, Botrytis sporulation in the lab occurred on petioles and rachises collected on the ground and remnants of rachises collected from canes after pruning.
- Eliminating pruning debris will remove the inoculum formed on decomposing clusters and pieces of canes prior to bud break. Vineyard access to alternate rows is required to incorporate last year's wood and cluster remnants while maintaining resident vegetation or a sown cover crop in the non-tilled rows.
All common grapevine fungal pathogens exist inside vineyards and the relative importance of allowing unsold fruit to remain on the vines should be put into perspective of other vine tissues that are also decomposing. Clusters that remain in the vineyard are not likely to have a noticeable effect on disease the following year if common vineyard floor management practices are followed.
Acknowledgement: Valuable input provided by Dr. Akif Eskalen, Cooperative Extension Plant Pathologist, UC Davis.
- Author: Karen Giovannini
We are pleased to welcome Cindy Kron, PhD as our Area Wide IPM Advisor for Sonoma, Napa, Mendocino and Lake counties.
Cindy has conducted research on a variety of insects including:
- two-year vineyard study on the population dynamics of Virginia creeper leafhopper, western grape leafhopper, and variegated leafhopper
- dissertation research projects investigating the biology and behavior of the three-cornered alfalfa hopper and their relationship with vineyards
- the effects of temperature on the developmental rate of the invasive European grapevine moth
- rearing brown marmorated stink bugs for USDA fumigation studies
Between UC Davis and UCCE, Cindy continued her study of the three-cornered alfalfa hopper as a Research Entomologist for USDA in their Crop Disease, Pests, and Genetics research unit. She tested additional cover crop species as feeding and reproductive hosts of the three-cornered alfalfa hopper in addition to testing commercially available biocontrol agents against the different life stages of the treehopper. She collaborated with a UC Davis colleague to create a degree day model that predicts the ideal timing to implement cultural control measures with the greatest impact on treehopper populations.
“My experiences have motivated me to help growers, stakeholders, and the industry solve agricultural pest management problems through applied research by identifying IPM strategies and tactics that are economically feasible and implementable while having the lowest environmental impact.”
When she is not working with insects, Cindy loves wine tasting, gardening, cooking and canning. She's come to the right place for ALL of that.
Welcome to Wine Country, Dr. Cindy Kron!
- Author: Rhonda Smith
- Editor: J. M.
Planting a vineyard with vines that are not infected with common grapevine viruses is essential to the bottom line. It can be challenging enough to keep over 1000 vines per acre relatively free from the normal canopy and trunk diseases such as grapevine powdery mildew and Eutypa dieback. Those diseases are caused by infections that occur naturally after vines are planted and can be controlled with proper farming practices.
Grapevine leafroll virus is an example of a common virus that can be avoided – at least initially – by planting certified vines. It is one of the viruses that cause the leaves of red-berried varieties to turn red in the fall. (The red “fall color” seen in photos of grapevines is not a good sign.) In white-berried varieties visual symptoms are more difficult to identify because the leaves do not turn red. Leafroll disease is widespread throughout the world and prevents the normal ripening process from occurring.
Unknowingly planting vines infected with leafroll virus is possible and very damaging because the virus is spread by mealybugs and scale insects. Starting with infected vines makes a bad situation worse because the incidence of diseased vines in a block quickly increases. Growers invest significant resources to control the insect vectors of leafroll, remove diseased vines and replant with clean stock.
UC Davis Foundation Plant Services
Starting out with “clean” vines is critical. And clean in this context means not infected with grapevine viruses that are known to reduce grape yield or quality. So it is important to plant a vineyard with vines that are far less likely to be infected on the day they are planted. In reality virus-free cannot be guaranteed.
To obtain the cleanest plants possible using normal nursery production practices, most growers purchase certified vines from grapevine nurseries and the source of those vines can be traced back to Foundation Plant Services (FPS) at UC Davis.
Vines are planted into Foundation Blocks at FPS only after undergoing a battery of virus tests – some of which can take two or more years - as prescribed by the CDFA regulations as well as pass other evaluations. The FPS lab continually tests for viruses in the Foundation Blocks; each vine is tested every three years. For nematode transmitted viruses, each Foundation vine is tested every two years.
Nearly 10 years ago, FPS began to develop a new Foundation Block that met newly established national standards for grapevine foundation plants in the US. The Russell Ranch Vineyard (RRV) at UC Davis contains Foundation vines which have all been propagated using a technique called microshoot tip culture – in which a 0.19 inch (0.5 mm) or smaller slice of the growing tip of a shoot is used as the starting material for a grapevine. These vines start out in small boxes on growth media. After a vine has grown large enough for tissue to be collected and tested for viruses, it must test negative for over 30 grapevine viruses.
Why so many? Because other countries have grapevine viruses that we don't have in the US, thus creating a testing protocol that includes those viruses helps to insure they are not in US Foundation Blocks. The testing protocol used to establish the RRV is known as “Protocol 2010” and it was made possible by funding in the 2008 Farm Bill that established the National Clean Plant Network (NCPN).
National Clean Plant Network
The purpose of the NCPN is to protect plants of economic value by diagnosing for plant pathogens, curing those plants, and to protect starter plants and make them available to industry. The goal of the NCPN is to sustain national funding for clean planting stock programs of key horticultural crops. There are five Grape Clean Plant Centers and they are located at UC Davis, Florida A&M University, Missouri State University, Cornell University and Washington State University. Clean Plant Centers also exist throughout the US for fruit trees, berries, citrus, hops, sweetpotatoes and roses. UC Davis FPS is also a Clean Plant Center for fruit trees, sweetpotatoes and roses.
“The National Clean Plant Network is an association of clean plant centers, scientists, educators, state and federal regulators, large and small nurseries and growers of specialty crops that work together to ensure that plant propagation material is clean and available.”
For more information on the National Clean Plant Network, visit nationalcleanplantnetwork.org
To learn more about Foundation Plant Services at UC Davis, visit fps.ucdavis.edu
Three of the twelve awards announced for the upcoming International IPM Symposium will be given to UC Integrated Pest Management Program members including Lucia Varela and Rhonda Smith from UCCE Sonoma.
The European Grapevine Moth Team was selected for an IPM Team Award for achieving the eradication of European grapevine moth only six years after its discovery in 2009. Team members helped growers in infested counties to monitor the pest and apply control measures on a timely basis. The team's research and extension efforts helped growers avoid losses to the pest every year until it was finally eradicated in 2016.
The European Grapevine Moth Team includes Lucia Varela, UC IPM advisor for the North Coast; Monica Cooper, UC Cooperative Extension viticulture advisor in Napa County; Walter Bentley, UC IPM entomologist emeritus; Larry Bettiga, UC Cooperative Extension advisor in Monterey County; Kent Daane, UC Cooperative Extension specialist in UC Berkeley Department of Environmental Science, Policy and Management; Rhonda Smith, UC Cooperative Extension advisor in Sonoma County; Robert Van Steenwyk, UC Cooperative Extension specialist in UC Berkeley ESPM; Joyce Strand, UC IPM academic coordinator emeritus; and Zalom.
The winners will receive their awards and recognition at the 9th International IPM Symposium March 19-22, 2018, in Baltimore, Md.
- Author: Karen Giovannini
2014 Annual Report letter from Stephanie Larson, County Director and Livestock & Range Management Advisor:
As we move into the next 100 years of Cooperative Extension, we continue to value the public/ private partnerships that have been the foundation of our organization, raising the bar by supporting the County of Sonoma Initiatives on local agriculture and healthy communities. UCCE advisors are critical partners with local farmers and ranchers, providing scientific-based information on techniques that can be used to increase production and thus increase economic stability, while addressing environmental concerns.
This past year, UCCE conducted research and provided educational programs to help commercial row crop farmers and livestock producers in Sonoma County deal with drought and climate change. Our frost tower research in vineyards evaluated methods for making the most of local water resources through increased irrigation efficiency. Water conservation programs are also focused on the urban gardener, partnering with the Sonoma County Water Agency to educate the public on how to use less water; and with the Agricultural Preservation and Open Space District to develop an evaluation tool for documenting ecosystem services that have been maintained or increased through implementing conservation easements and proper rangeland management.
We partnered with other county departments to increase access to healthy, local, sustainable food. One outcome was the County Land for Food Production (CLFP) project; which allowed UCCE to work on creating an incubator farm on county land. These efforts are aimed at increasing access to land for food production, and the number of farmers and ranchers growing local food, respectively. The goals align with the Sonoma County Healthy and Sustainable Food Action Plan. Our Agricultural Ombudsman played a critical role in assisting individuals who want to create or expand their farming and ranching enterprises, and is currently working with PRMD to address local poultry processing.
Learn about these programs and more in our 2014 Annual Report.