Survival of navel orangeworm (Lepidoptera: Pyralidae) during pistachio processing

The potential survival of the navel orangeworm, Amyelois transitella (Walker), in pistachios after commercial processing was estimated by sampling nuts from 2 different driers. In total, 1,980 kg of pistachios (approximate to 880,000 open nuts) were sampled over 3 yr. No live navel orangeworm were found and only 1 dead adult was discovered. Samples from drum driers, which received floaters, had an average of 10.7 dead navel orangeworm per Idiogram of nuts, whereas samples from the fan driers had an average of 1.9 dead navel orangeworm per kilogram of nuts. The occurrence of moths in traps baited with virgin, laboratory-reared females suggests that some navel orangeworm survive processing, but it was not possible to determine the source of the moths. Commercial pistachio drying was simulated in a forced-air oven with an air temperature of 90 degrees C. Nut temperatures during laboratory oven drying exceeded 60 degrees C after 45 min, when nut moisture levels were >26%. Nut temperatures were >60 degrees C for 2.25 h before nut moisture content approached appropriate storage levels. Limited survival of navel orangeworm eggs (2.82%) and pupae (3.33%) occurred after 30 min of oven exposure, when not all nut temperatures had exceeded 60 degrees C. No navel orangeworm survived oven exposures of 1 h or longer. Our results show that survival of navel orangeworm in processed pistachios is very low and should not be of major concern to processors.