George M. Leavitt, Jr., UC Cooperative Extension viticulture advisor emeritus for Madera County, passed away in Paso Robles on April 21, 2025. He was 79.
Leavitt served as the UCCE viticulture farm advisor for Madera County from 1975 until his retirement in 2006. During his 34-year UCCE career, he was recognized as an exceptional plant pathologist specializing in grapevine trunk diseases like Botryosphaeria, Eutypa and Phomopsis dieback.
Prior to becoming a UCCE viticulture farm advisor, Leavitt worked as a staff research associate for the distinguished UCCE viticulture specialist Fred Jensen. While finishing up his master’s degree at Brigham Young University, Leavitt found it was the perfect job because Jensen led a busy lab focused on evaluating plant growth regulators and cultural operations for table grape production.
Leavitt would go on to use the trial methodology in his own large field trials that became popular with Madera County growers. After Jensen’s retirement, Leavitt would check in with him regularly to discuss industry issues over lunch, which often included Larry Bettiga, UCCE viticulture farm advisor in Monterey County and former Jensen staff research associate.
“George arranged a lunch meeting every year and we continued to meet annually after Fred’s passing for a Jensen memorial luncheon,” Bettiga said.
In the early 1980s, Leavitt began work on his Ph.D. He took a sabbatical to complete his course work at UC Riverside and returned to Madera to continue and finish his field work, which was focused on grapevine canker diseases, under the tutelage of Donald E. Munnecke, Ph.D., at UC Riverside, whose philosophy was that fieldwork made the researcher. Leavitt had been working with growers to identify the cause of dying cordons and noticed the symptoms varied greatly and didn’t fit the traditional tattered leaf symptoms that E. lata is known to cause.
Leavitt took Munnecke’s adage to heart and collected numerous samples from California, Arizona and northern Mexico vineyards, documenting symptoms, collecting samples, spending hours in the laboratory, plating them on auger plates and looking through a microscope to identify the different fungi. His hard work paid dividends, because he determined that Botryosphaeria theobromae was the other fungus infecting grapevines, causing “Bot canker.”
After retirement, Leavitt mentored early-career plant pathologists working on canker diseases who brought a different set of skills and approach to working on grapevine cankers, which was primarily focused on lab research. However, he would gently remind them of the importance of collecting their own field samples.
Growers regarded Leavitt as a consummate professional and educator. “You could always count on learning something from him,” said Kip Green, a former vineyard manager and current Pest Control Adviser and Certified Crop Adviser. “George was generous with his time and always made sure you had the information to make the right decision in the vineyard.”
Leavitt held monthly grower meetings at the Howard School building in Madera, which was turned into a restaurant by local caterer, Dino Petrucci, who renamed it “Old School House.” Petrucci, a grape grower himself, made sure his grower colleagues didn’t go hungry, serving up tri-tip sandwiches, potatoes, beans, salad and dessert for $10! Growers would meet for lunch and receive one hour of continuing education credit to maintain their Private Applicator License.
Leavitt would often present a topic, but would also have his UC ANR colleagues give talks on relevant grape issues, like insect pests or weeds. A grower once said “You never leave George’s meeting hungry or bored. The discussion is always lively.”
In addition to working on grapevine trunk diseases, Leavitt also conducted powdery mildew fungicide trials at a local grower’s vineyard. The trials were extensive, often having 30-plus treatments that included multiple combinations of registered and experimental fungicides. Grape growers from Bakersfield to Modesto would attend the field day to learn about the latest products.
Stephen Vasquez, a former UCCE viticulture advisor who served in Fresno County for 14 years, attended the field days and described them as a “who’s who of the grape industry.” “Everyone wanted the information so they could prepare for the next season,” Vasquez said.
Tome Martin-Duvall, a former UC technician who worked for Leavitt and oversaw the powdery mildew trials, mentioned that 50 to 100 growers would attend the field days.
“Bad mildew the previous season would result in increased attendance the next season,” said Martin-Duvall. “You could often meet up with other UCCE farm advisors, too, because they wanted to share the trial data with their growers.”
After retiring in 2006, Leavitt remained involved in the grape industry and research. He supported UC colleagues by presenting at their local meetings on grapevine disease management. He also worked with international colleagues on separating grapevine fungal pathogens using DNA technology.
“He never lost interest in viticulture research,” said Vasquez. “He always wanted the newest information so he could share it with his grower friends in the San Joaquin Valley.”
Leavitt made significant contributions to California viticulture and was recognized by the University of California, the California Association of Pest Control Advisers and the San Joaquin Valley Winegrowers Association for his research and extension program.
Leavitt is survived by his wife Annette, seven children, 36 grandchildren and six great-grandchildren.
Funeral services for Leavitt will be held on Saturday, May 3, 2025, at 11 a.m. at The Church of Jesus Christ of Latter-Day Saints, 2600 Ramona Road, Atascadero, California. Those wishing to honor Leavitt’s life can make donations to Court Appointed Special Advocates San Luis Obispo at slocasa.org.