California Pistachios: Timing This Year’s NOW Sprays

    Navel Orangeworm. Photo: USDA

    Hey, did you hear about the two pistachio farmers who pulled their pickups next to one another to ask what the price of worms was this year? The answer is up to 20 cents more per pound from base price for super quality.

    We have to have clean nuts to run the marketing program, folks. One processor had 400 of their 700 employees on the belts looking for infested nuts last year. Until we can come up with a more sophisticated identification process, this is what processors have to do to keep consumers buying an expensive product.

    Research by USDA’s Dr. Joel Siegel suggests that 1700, 2200 and 2700 Degree Days from January 1 are key times for evaluation of your NOW population, since they mark rises in NOW activity. Evaluation does not mean blanket spraying.

    But NOW Can Work Even Faster Than That

    Dr. Siegel’s research confirms that NOW cycles much faster on new pistachios – so much so that they can actually complete a generation in 500-600 DDs.

    Dr. Martin Barnes (“Dr. NOW” of the 1970’s at UC Riverside) also reported this back in the 1970’s. Hence, Dr. Siegel suggests orchards under high NOW pressure may require re-treatment at 2200 and 2700 DD0 from January 1.

    The need to do this in your orchard is a decision between you and your crop consultant, SO you need to get together with your crop consultant NOW to discuss what they are seeing and what they recommend you do. According to the Degree Day monitoring service Dow AgroSciences, the overwintering NOW generation just ended about June 18.

    Take Into Account The Spillover From Almonds

    This is six days later than last year. The beginning of the second generation is going to fall right on top of the early suture development in almonds, which could increase that crop’s insect pressure.

    It could also spill over into pistachios later when the almonds are harvested, so try to stay abreast of what your almond neighbor is doing to protect his crop.

    The impact of the second flight greatly increases in pistachios with the occurrence of early pea split nuts. Pea split nuts allow the overwintering generation of NOW to transition onto the “new crop”, and thus develop at a faster rate, due to the improved food source.

    Pea splits typically do not occur before the first week in July. Don Thomas, a crop scout for 30 years, tells me that 25 pea splits found in three minutes spells big trouble, so get out in the orchard and monitor for these! Don’t ask your crop advisor to do it all.

    Feet On The Ground – Including The Grower’s

    There is no way they can spend the time scouting your field the way you can. Help them out, so you can help yourself get that 20 cent premium.

    Dr. Siegel has developed an outstanding table to assist growers in their NOW management decisions. His table does NOT constitute a recommendation! Use this very valuable tool in your discussions with your crop advisor to customize your pest management program.

    In order to provide this table for this article, Dr. Siegel agreed to share this draft with us. Changes to this table will be posted on my Kings County web page.

    How Much Longer Can We Count On Pyrethroids?

    Dr. Siegel also reminded me of published research by University of Illinois in cooperation with entomologist Brad Higbee (formerly with Wonderful, and now with Trece) that showed pyrethroid resistance development. At the time of the study, NOW’s tolerance to pyrethroid was reportedly as high as 16 times the control group. I am told that field failure can begin when tolerance reaches 20-fold.

    Dr. Siegel’s colleagues at the University of Illinois also showed resistance remained stable for at least 10 NOW generations under laboratory conditions. Although pyrethroids are still effective in the field today, our heavy reliance upon them may come to an end due to resistance.

    Dr. Siegel states that there is also no new chemistry within the pyrethroid class to explore. This information makes timing and execution of treatments all the more important. Between the difficulty in thoroughly winter sanitizing pistachios, and the thousands of acres of nut crops now present in the southern San Joaquin Valley with varying degrees of NOW management, it is no surprise that attempts to apply IPM principles prove very difficult.

    For that reason, I hope to see mass mating disruption in pistachio and almond before I take my last breath.

    Click Table To Enlarge

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