ARS | Publication request: Use of Low Temperature to Control Postharvest Indianmeal Moth

Submitted to: Australian Nutgrower
Publication Type: Trade Journal
Publication Acceptance Date: May 20, 2009
Publication Date: June 10, 2009
Repository URL: http://hdl.handle.net/10113/36417
Citation: Johnson, J.A. 2009. Use of Low Temperature to Control Postharvest Indianmeal Moth. Australian Nutgrower. 23(2):6-8.

Interpretive Summary: Insects often pose a significant challenge to nut producers, not only in the orchard, but in the processing plant and warehouse. Historically, the most common method to disinfest product of insects is to use chemical fumigants, but concerns over worker and environmental safety has generated great interest in non-chemical alternative methods. Because insects are cold-blooded their body temperature varies with that of the ambient environment. Consequently, manipulation of the temperature in storage environments may be a useful technique to manage populations or disinfest product. The Indianmeal moth is often the most serious pest of postharvest tree nuts, and has been the target of numerous studies examining the possible use of temperature for its control. Eggs are the least tolerant of low temperatures. Non-diapausing larvae are a little less tolerant than pupae at 0C and 5C, but larvae show a much greater tolerance than pupae at 10C. Diapausing larvae require much lower temperatures before mortality occurs. At -10C exposures of 17-20 days were required to kill 95% of diapausing larvae, while exposures of one day or less were needed at -15C and -20C. Low temperature storage at 10C was effectively combined with short-term disinfestation methods such as low-oxygen treatments in a pest management strategy for California postharvest almonds and walnuts. Storage of tree nuts at 10C prevented Indianmeal moth populations from building up to detectable levels. At 10C, the life span of adult Indianmeal moths is extended. Average adult lifespan is about 2 weeks at 27C, while it is roughly 50 days at 10C, with some adults surviving to 80 days. However, female moths exposed to 10C for 25 days or longer either before or after mating produced less than half as many eggs as normal, and only 10% of the eggs produced were viable.

Technical Abstract: The restrictions on the use of fumigants for product disinfestation due to worker safety or environmental concerns has increased interest in non-chemical alternatives. The Indianmeal moth is often the most serious pest of postharvest tree nuts, and has been the target of numerous studies examining the possible use of temperature for its control. Eggs are the least tolerant to low temperatures. Non-diapausing larvae are a little less tolerant than pupae at 0C and 5C, but larvae show a much greater tolerance than pupae at 10C. Diapausing larvae require much lower temperatures before mortality occurs. At -10C exposures of 17-20 days were required to kill 95% of diapausing larvae, while exposures of one day or less were needed at -15C and -20C. Low temperature storage at 10C was effectively combined with short-term disinfestation methods such as low-oxygen treatments in a pest management strategy for California postharvest almonds and walnuts. Storage of tree nuts at 10C prevented Indianmeal moth populations from building up to detectable levels. At 10C, the life span of adult Indianmeal moths is extended. Average adult lifespan is about 2 weeks at 27C, while it is roughly 50 days at 10C, with some adults surviving to 80 days. However, female moths exposed to 10C for 25 days or longer either before or after mating produced less than half as many eggs as normal, and only 10% of the eggs produced were viable.