Author
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Johnson, Judy |
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Submitted to: International Conference on Methyl Bromide Alternatives and Emissions Reductions
Publication Type: Proceedings Publication Acceptance Date: 9/16/2008 Publication Date: 11/11/2008 Citation: Johnson, J.A. 2008. Vacuum treatments for California tree nuts. International Conference on Methyl Bromide Alternatives and Emissions Reductions. 71.1-4. Interpretive Summary: California walnuts, almonds and pistachios must be free of insect infestation to meet consumer demands and export requirements. Fumigants such as methyl bromide are used to disinfest tree nuts of field pests such as codling moth and navel orangeworm, and storage pests such as Indianmeal moth. The development of inexpensive, portable, flexible containers facilitates the use of vacuum treatments as a non-chemical alternative to methyl bromide and other fumigants. Because the method by which vacuum treatments cause death is partially dependent on drying, product moisture has an effect on treatment efficacy. Also, Indianmeal moth and codling moth overwinter as diapausing larvae, which often are more resistant to fumigants and other disinfestation treatments. The current laboratory study showed that high humidity resulting from high moisture products may reduce effectiveness of vacuum treatments by reducing water loss in target insects. The study also shows that moisture loss in diapausing Indianmeal moth is less than in nondiapausing larvae, and may account, in part, for increased tolerance to vacuum found in diapausing larvae. Field studies showed that successful treatments were obtained after 48 hour exposures at 50 mm Hg, but target pressures were sometimes difficult to reach due to small leaks. Preventing rodent damage may also be very important to overall success of this treatment. Treatment success should be improved by including product moisture levels and increased tolerance of diapausing insects when developing treatment schedules. Technical Abstract: California walnuts, almonds and pistachios must be free of insect infestation to meet consumer demands and export requirements. Fumigants such as methyl bromide have long been used to disinfest tree nuts of field pests such as codling moth and navel orangeworm, and storage pests such as Indianmeal moth. The development of flexible, inexpensive, portable containers has made possible the use of vacuum treatments as a non-chemical alternative. Because the mechanism of vacuum treatments is partially dependent on the drying effect of reduced oxygen and low atmospheric pressures, product moisture has an effect on treatment efficacy. The current study showed that high humidities resulting from high moisture products may reduce efficacy of vacuum treatments by reducing water loss in target insects. Treatment success should be improved by including product moisture levels in developing treatment schedules. Our study also shows that diapausing Indianmeal moth are able to reduce their moisture loss when compared to nondiapausing larvae. This ability accounts in part for the increased tolerance to vacuum found in diapausing larvae. Field studies showed that successful treatments were obtained after 48 hour exposures, but that obtaining target pressures were sometimes difficult due to small leaks in the bags caused by wear. Preventing rodent damage may also be very important to overall success of this treatment. |
