Author
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Johnson, Judy |
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Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 5/19/2007 Publication Date: 8/1/2007 Citation: Johnson, J.A. 2007. Survival of Indianmeal moth, Plodia interpunctella, and navel orangeworm, Amyelois transitella, (Lepidoptera: Pyralidae) at low temperatures. Journal of Economic Entomology. 100(4)1482-1488. Interpretive Summary: A major problem in the storage of California dried fruits and tree nuts is infestation by postharvest insect pests, including field pests such as navel orangeworm, and common stored product pests like Indianmeal moth. Currently, processors depend on fumigation with methyl bromide or phosphine to disinfest large volumes of incoming product after harvest, and to control insects during storage. Recent concerns over resistance, regulatory action and the needs of the organic industry have generated a renewed interest in developing non-chemical alternative treatments. Low temperatures have been used to control other stored product insects, and show potential for postharvest dried fruit and nuts. We determined the susceptibility of various life stages of Indianmeal moth and navel orangeworm to 0, 5, and 10C at different humidity levels, and also examined the response of diapausing Indianmeal moth larvae to -10, -15 and -20C. Eggs of both species were the most susceptible to low temperatures. At 0 and 5C pupae were most tolerant, but at 10C, non-diapausing larvae of both species were very tolerant, requiring 127 and 100 days exposure for 95% mortality of Indianmeal moth and navel orangeworm, respectively. Diapausing Indianmeal moth larvae were very tolerant to -10C, with 17-20 days needed for 95% mortality, but were far less tolerant at lower temperatures. At -15 95% mortality occurred at 14-23 hours, and at -20C 95% occurred at 6-7 hours. Refrigeration at 0-5C should be useful in disinfesting product of non-diapausing insects, with estimated storage times of 3 weeks needed for adequate control. Relatively brief storage in commercial freezers (-18C), provided the temperature throughout the product was below -15C for at least 48 hours, also shows potential as a disinfestation treatment, and is necessary when diapausing Indianmeal moth larvae are present. Technical Abstract: Concerns over insect resistance, regulatory action and the needs of organic processors have generated renewed interest in developing non-chemical alternative postharvest treatments to fumigants used on dried fruits and nuts. Storage at low temperatures has been identified as one such alternative for the Indianmeal moth, Plodia interpunctella (Hubner), and navel orangeworm, Amyelois transitella (Walker), common postharvest pests in California dried fruits and nuts. The response of eggs, non-diapausing larvae and pupae of both species to exposure to low temperatures (0, 5 and 10C) was evaluated. Eggs of both species were the least tolerant to low temperatures. At 0 and 5C pupae were most tolerant, but at 10C, non-diapausing larvae of both species were most tolerant, with LT95s of 127 and 100 d for Indianmeal moth and navel orangeworm, respectively. The response of diapausing Indianmeal moth larvae to sub-freezing temperatures was also evaluated. Diapausing larvae were very cold tolerant at -10C, with LT95s of 20 and 17 d for long-term laboratory and recently isolated cultures, respectively. Diapausing larvae were far less tolerant at lower temperatures. At -15 LT95s for both cultures were <23 h. and at -20C LT95s were <7 h. Refrigeration temperatures of 0-5C should be useful in disinfesting product contaminated with non-diapausing insects, with estimated storage times of 3 wk needed for adequate control. Relatively brief storage in commercial freezers, provided that the temperature throughout the product was below -15C for at least 48 h, also shows potential as a disinfestation treatment, and is necessary when diapausing Indianmeal moth larvae are present. |
