Strategies to Manage Bot in Pistachios and Walnuts

Because prices for pistachios and walnuts are still relatively good this season, growers will be able to get the most out of their existing orchards, and some growers may plant more pistachios. When there’s an opportunity to make a profit, growers should fine-tune their fungicide programs to optimize quality and yield.

“Botryosphaeria disease [bot] concerns are amplified when spring precipitation is plentiful,” says Themis Michailides, Ph.D., plant pathologist at the University of California’s Kearney Agricultural Research and Extension Center in Parlier. “Bot infections should be managed diligently by pistachio and walnut growers. Even a light sprinkling can facilitate the spread of Botryosphaeria panicle and shoot blight in pistachios and Botryosphaeria blight and canker in walnuts.”

Fungicide Efficacy for Bot in Pistachios
Research conducted at the University of California has demonstrated the benefits of a spring and early summer fungicide program. “For example, DuPont™ Fontelis® fungicide is an excellent spring option for controlling bot in pistachios,” says Jeff Pacheco, a DuPont Crop Protection technical sales agronomist. “Although control of bot is more difficult in walnuts, growers can significantly reduce disease incidence with foliar applications of fungicides applied in mid-May, mid-June and mid-July.”

Practice Smart Resistance Management
“Fungicide resistance does not appear to be a problem with Botryosphaeria in pistachios or walnuts, but we still recommend rotating fungicides,” says Michailides. “In pistachios, it’s important to remember that alternaria late blight resistance can be a concern in some orchards with certain classes of fungicides. It’s wise to tank-mix fungicides with different modes of action or use rotation as part of a resistance management program for this particular disease.”

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