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April 2018 WINES&VINES 25 VINEYARD VIEW Biopesticides are used by grow- ers participating in the National Organic Program and Biodynamic farming because they are the only pesticides that meet the require- ments of their respective certifica- tion standards. Since the acreage enrolled in these programs is in- creasing, the use of biopesticides is increasing as a result. Further- more, there are several sustainable winegrowing certification pro- grams in California, Oregon and New York that encourage the use of reduced-risk pesticides, making biopesticides a good fit. The acres of vineyards enrolled in these pro- grams continue to increase, which should also increase the use of biopesticides. In talking with university ex- tension farm advisors, there still seems to be a learning curve for some growers when using biopes- ticides. They do not realize that timing of treatment in relation to the pest life cycle or disease pres- sure is much more critical than with conventional pesticides. Many growers have the "once burned, twice shy" attitude to- ward pesticides, so a bad experi- ence affects their choice of pesticide for a long time. One significant case study that demonstrates the efficacy of properly used biopesticides is in the successful eradication of the E u r o p e a n g r a p e v i n e m o t h (EGVM) in Napa Valley. Eradica- tion of an introduced pest, par- ticularly one as prolific as EGVM, is very challenging for many reasons, and success is rare. Nev- ertheless, some growers partici- pating in the eradication efforts used a range of biopesticides including materials containing Bacillus thuringiensis and spi- nosad. Growers using these tools were very aware of their shorter residual effects compared to con- ventional pesticides and there- fore timed their applications to match the predicted life cycle of EGVM, particularly in the first generation. They were also will- ing to make the numerous neces- sary applications to maximize efficacy. Pheromone confusion was also part of the management programs used by some growers. It was concluded that growers using biopesticides played a critical role in the successful eradication of EGVM. Even though the overall use of biopesticides in U.S. vineyards is still only a very small portion of the total pounds of active in- gredients applied for pest-man- agement control, it is clear they play an important role in specific situations where reduced-risk pesticides are either required or fit into the philosophy and strat- egy of sustainable wine grape growers. Cliff Ohmart, Ph.D., was a senior scientist for SureHarvest for 8 years and author of View from the Vineyard: A Practical Guide to Sustainable Wine Grape Grow- ing. Previously he served as research/ IPM director at the Lodi-Woodbridge Winegrape Commission. He has been writing about sustainable winegrowing issues for Wines & Vines since 1998. BIOPESTICIDES COME IN TWO CLASSES B iopesticides are naturally occurring chemi- cals or micro-organisms that control pests through various modes of action. They come in two basic classes: 1) microbials, which are microorganisms such as fungi, bacteria, viruses, protozoans and nematodes; and 2) biochemicals, such as pheromones and plant extracts that are not directly toxic to the pest, or fatty acids and soaps. Microbials used to control arthropods (e.g. insects, spiders, and mites) have a range of modes of action, depending on the type and species of microbe. Some produce a toxin that kills the pest when ingested, such as Bacillus thuringiensis (Bt). Some bacteria and viruses are ingested by an arthropod, reproduce inside it, killing it through production of toxins such as nuclear polyhedrosis viruses (NPVs). Some fungi enter an arthropod and produce mycelia that literally fills up the body cavity of the host, killing it. Other microbes do not kill their host but render it ineffective as a pest. I encountered my favorite example of this type in my days as a forest entomologist: It is a nematode para- site of a woodwasp pest of Monterey pine. It enters the female wasp larva, feeding inside the tree trunk and migrating to where the ovaries will form when the wasp larva pupates. It then produces young nematodes that enter the wasp eggs when they are forming in the ovaries of the adult wasp. Instead of laying viable eggs, the female woodwasp lays eggs that contain a nematode rather than a wasp embryo. The nematode emerges from the egg, finds new female woodwasp larvae to infest, and the cycle starts all over again. The nematode does not kill the woodwasp larva or adult but sterilizes the adult female. Microbials effective in controlling fungal diseases do so using a range of modes of ac- tion that are specific to the microbe species. Some prevent disease by colonizing the plant surface—causing no damage to the plant, while preventing the target pathogen from getting established on the plant surface. Other microbe species produce compounds that interfere with germination of the spores or growth of the pathogen. Pheromones are volatile compounds released by females of many of insect species for the purpose of attracting their male counterparts for mating. Chemists have identified the chemi- cal makeup of the pheromone for some insects such as vine mealybug, European grapevine moth and omnivorous leafroller, and developed a process for synthesizing them. It can then be put in the dispensers for pheromone traps and pheromone confusion programs. Fatty acids and soaps such as Kaligreen and M-pede kill arthropods by dissolving the cuticle on the outside of their bodies, causing them to lose moisture and desiccate. Another group of naturally derived biochemicals, called SARs, which stands for systemic acquired resistance, stimulate a treated plant to produce biochemi- cal, reducing its susceptibility to pests, sort of like creating an immune response. PESTICIDE USE IN CALIFORNIA WINE GRAPE VINEYARDS Pesticide Active Ingredient (AI) Pounds Applied in 2005 Pounds Applied in 2015 Pyrethin 194 217 Bacillus amyloliquefaciens (Double Nickel) Not registered 19,216 Bacillus thuringiensis (Dipel) 8,088 6,306 QST 713 Bacillus subtilis (Serenade) 21,596 42,821 Bacillus pumilus (Sonata) 1,126 2,366 Spinosad 804 313 Total pounds of biopesticides applied to wine grapes 31,808 71,239 Total pounds of AIs applied to wine grapes 29,796,746 29,022,331 Pounds of sulfur dust applied to wine grapes 25,038,184 21,929,487 Pounds of all AIs minus sulfur dust applied to wine grapes 4,758,562 7,092,844 Percent biopesticides minus sulfur dust 0.67% 1.00% Source: California Department of Pesticide Regulation