Navel orangeworm is still the pest to beat this season. Although many growers have sufficiently low NOW pressure to require only two sprays, many growers exposed to high populations have applied five or more sprays for both plant bug and NOW. The 2700 DD timing occurred about August 1.
Dr. Joel Siegel, USDA-ARS, says there is enough additional degree days for possibly a fifth generation of NOW in the fall, so be sure to survey what is left in the trees after harvest, and get it on the ground if you can early to reduce your overwintering population. We are also seeing a substantial number of fully developed early split nuts this year, so now is the time to walk your orchards and look for egg laying, even if you applied a spray at 2700 DD.
Carry a hand lens and look in the crevices of the split for white and salmon colored eggs. Go to the UCIPM website for egg photos to reference. Also be on the lookout for newly hatched larva, which tells you the egg was laid about four days earlier.
Weekly monitoring of split and mature nuts during harvest is a must. The research data shows pistachio worm damage can increase by one-third to one percent per week, depending upon the season. Aerial applications have looked good in Joel’s research as cover sprays during harvest. Be sure to use a material that kills adults.
Remember that prompt harvest is one of the BEST control methods for NOW! Dr. Siegel’s NOW infestation rate curve for Kings County suggests growers have about 21 days from the very beginning of harvest before NOW damage goes off right a Saturn rocket. Review of the payment penalty now assessed by most processors for offgrade, including insect, shows how costly wormy nuts become.
The buyers are also looking for a way to beat back the pricing structure on pistachios, so do all you can to deliver clean crop!