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After nearly 35 years of helping Central Coast growers battle invasive pests and diseases, Bill Coates, UC Cooperative Extension farm advisor and county director for San Benito County, will retire June 29.

Coates serves as an advisor for growing tree fruits and nuts in San Benito, Santa Cruz, Santa Clara and Monterey counties. He is internationally renowned for his expertise in walnut husk fly management, but has contributed to advances in pest control and growing practices for many crops.

Coates has been “indispensible,” said Vince Gizdich, a Santa Cruz County grower. “He’s a walking encyclopedia with all those years of knowledge.”

“He’s been able to save farmers from catastrophe,” Gizdich said, recalling the time when Coates alerted him to symptoms of European canker so he was able to eradicate the disease before it destroyed his apple trees.

“I have worked with hundreds of farmers and I appreciate the chance to help them,” Coates said. “In lots of cases, they helped me by bringing problems I hadn’t observed to my attention, problems that ended up as research projects. It’s a mutually beneficial relationship.”

Much of Coates’ research has been aimed at reducing the amount of pesticides needed by precisely timing applications. For apricots, his research revealed that post-bloom sprays were effective in controlling leafrollers. He has also helped develop new chemical control measures for codling moth in both walnuts and apples, by themselves or combined with pheromone mating confusion.

The walnut husk fly has been a nemesis for most of his career. Coates developed a method that has become the industry standard for estimating the economic impact of walnut husk fly damage to English walnut quality. With UC Berkeley colleague Bob Van Steenwyk, Coates has tested pesticides and developed effective organic materials and techniques for controlling the walnut husk fly.

“Bill has been on the front line testing organic materials with Bob Van Steenwyk, and now we have a lot certified for organic farmers,” said Al Bonturi, who has grown apricots, prunes and grapes in addition to walnuts in San Benito County.

“He’s the guy who got the blackline resistant variety program in gear,” said Bonturi, a former San Benito County Farm Bureau president. Spread by contaminated pollen, walnut blackline disease can eventually choke the life out of walnut trees.

For most of his career, Coates has worked with growers to evaluate which new walnut varieties that are resistant to walnut blackline disease will grow best on the Central Coast. Coates compares blooming dates, harvest dates, nut quality and quantity of the different varieties.

“With late varieties, we end up harvesting in rain so we want early varieties,” Bonturi explained. “Now we’ve got 10 to 12 varieties that are resistant, but UC hasn’t released any yet.”

In 2009, a new insect, spotted wing drosophila, began infesting cherries in Santa Clara County. Coates was instrumental in helping to identify the culprit and worked with other UC scientists to develop emergency control measures to limit the damage.

Growing up in Bakersfield, Coates became interested in growing plants while working with his father in the family’s vegetable garden.

“I was in charge of the fruit trees in my yard,” Coates recalls. His high school didn’t offer agriculture classes, but he learned how to grow fruits and vegetables from publications that he bought from the local UC Cooperative Extension office.

During college, he worked for UC Cooperative Extension postharvest specialist Gordon Mitchell and staff research associate Gene Mayer in the UC Davis Pomology Department for five years.

After earning his bachelors in plant science and master’s degrees in horticulture from UC Davis, Coates began his career with UC Cooperative Extension in 1976 as a farm advisor for tree fruit, nuts, grapes and vegetable crops in San Benito County. In the 1980s he added Monterey County to his responsibilities, leaving grapes and vegetable crops to other farm advisors. In the 1990s, after other farm advisors retired, his area expanded to include Santa Cruz and Santa Clara counties.

In 1986, Coates became county director for UC Cooperative Extension in San Benito County, serving until 1999. He was asked to be county director again in 2007.

Gizdich praised Coates’ newsletter “Tree Topics” for keeping growers apprised of what to look out for in the coming season.

““Tree Topics” always has wonderful information – spray tips, good information about chemicals – important stuff one would have to go to college to get, we get in the newsletter when it’s necessary,” he said.

During retirement, Coates, who has been granted emeritus status by UC, plans to continue working on three major research projects – spotted wing drosophila, walnut husk fly and blackline-resistant walnut varieties.

Coates said, “I would like to continue to develop new research and assist local growers as my time allows.”