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United States Department of Agriculture

Agricultural Research Service

Title: Response of postharvest tree nut lepidopteran pests to vacuum treatments

Authors
item Johnson, Judy
item Zettler, James

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 17, 2009
Publication Date: October 5, 2009
Repository URL: http://hdl.handle.net/10113/36433
Citation: Johnson, J.A., Zettler, J.L. 2009. Response of postharvest tree nut lepidopteran pests to vacuum treatments. Journal of Economic Entomology. 102(5):2003-2010.

Interpretive Summary: A major problem in the storage and marketing of California tree nuts is infestation by a variety of postharvest insect pests, such as navel orangeworm, codling moth, and Indianmeal moth. To avoid invasion by these pests, importing countries may require phytosanitary inspections or treatments before allowing California nut products entrance to their markets. Currently, tree nut processors depend on fumigation with methyl bromide or phosphine to disinfest large volumes of incoming product after harvest, and to control infestations during storage. Regulatory actions against methyl bromide as well as insect resistance to hydrogen phosphide may make these fumigants costly or unavailable to the nut industry. Also, as the organic industry expands the need for non-chemical postharvest insect control methods increases. These concerns have generated a renewed interest in developing non-chemical alternative treatments. One possible non-chemical alternative is the use of low atmospheric pressures (vacuum), to disinfest product. Flexible polyvinyl chloride containers developed for temporary grain storage have utility as vacuum treatment containers, making the treatment more economical and practical. This paper investigates the potential of vacuum for disinfesting postharvest tree nut pests by first determining the relative tolerance to low pressures of different life stages of target pests, and then conducting field tests with almonds treated under vacuum in 5 MT PVC containers. Navel orangeworm eggs were most tolerant to vacuum. Diapausing codling moth and Indianmeal moth larvae were similar in tolerance to egg stages, and non-diapausing codling moth larvae were the least tolerant stage tested. Field tests using PVC containers to treat shelled almonds in bins at vacuum levels of 18-43 mm Hg at average winter temperatures (6-10C) showed that diapausing codling moth larvae were the most tolerant, and that exposures of 7-13 days provided incomplete control. Summer field tests treating inshell almonds in bags at average temperatures of 25-30C provided complete control with 48 h exposure to average vacuum levels of 50 mm Hg, and navel orangeworm eggs were the most tolerant stage.

Technical Abstract: Industry concerns over insect resistance, regulatory action, and the needs of organic processors have renewed interest in nonchemical alternative postharvest treatments to fumigants used for California tree nuts. The development of inexpensive polyvinyl chloride containers capable of holding low pressures has increased the practicality of vacuum treatments for durable commodities such as tree nuts. To develop vacuum treatment protocols, we determined the relative tolerance to vacuum (50 mm Hg) at 25 and 30°C of different life stages of three postharvest pests of tree nuts; codling moth, Cydia pomonella (L.), navel orangeworm, Amyelois transitella (Walker), and Indianmeal moth, Plodia interpunctella (Hübner). Navel orangeworm eggs were most tolerant to vacuum (LT95s = 26.9 and 26.1 h at 25 and 30°C, respectively). Diapausing codling moth and Indianmeal moth larvae were similar in tolerance to egg stages, and non-diapausing codling moth larvae were the least tolerant stage tested. Field tests using GrainPro Cocoons to treat shelled almonds in bins at vacuum levels of 18-43 mm Hg at average winter temperatures (6-10°C) showed that diapausing codling moth larvae were the most tolerant, and that exposures of 7-13 days provided incomplete control. Summer field tests treating inshell almonds in bags at average temperatures of 25-30°C provided complete control with 48 h exposure to average vacuum levels of 50 mm Hg, and navel orangeworm eggs were the most tolerant stage.

Last Modified: 4/16/2014
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