Author
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Johnson, Judy |
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Valero, Karen |
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Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 8/8/2003 Publication Date: 12/1/2003 Citation: Johnson, J.A., Valero, K.A. 2003. Use of Commercial Freezers to Control Cowpea Weevil, Callosobruchus Maculatus (Coleoptera: Bruchidae), in Organic Garbanzo Beans. Journal of Economic Entomology. 96 (6): 1952-1957. Interpretive Summary: A serious postharvest pest of stored beans and peas is the cowpea weevil, Callosobruchus maculatus (F.) (Coleoptera: Bruchidae). Cowpea weevil larvae feed hidden within the seeds of many different legumes, and populations may grow unnoticed to severely damaging levels. Within the U.S., cowpea weevil infestations in postharvest legumes are controlled with the chemical fumigants methyl bromide and phosphine. Regulatory loss of methyl bromide, the possible restriction of phosphine, and the rising popularity of organic product lines, has created interest in non-chemical disinfestation treatments. One alternative is the use of cold storage. A bean processor with ready access to a nearby commercial cold storage facility has successfully used 30-day exposures to -18 degrees C to disinfest organic garbanzo beans of cowpea weevil. We believed that a 30 day exposure might be unnecessarily long. To develop more useful recommendations, we determined the most cold tolerant stage of the cowpea weevil, and the exposure times needed for control of cowpea weevils in bulk-stored garbanzo beans under commercial freezer conditions. We found the egg stage was most tolerant to -18 degrees C, and that adults were most susceptible. To examine the efficacy of cold storage disinfestation, bags of blackeyed peas infested with cowpea weevil eggs were buried within garbanzo bean bins placed in a commercial cold storage facility kept at about -18 degrees C and removed after 7, 14 and 21 days. Survival was highest in eggs located at the center of the bins, and coincided with the slowest cooling rate. Although temperatures within the bins did not reach -18 degrees C until after 14-19 days, egg mortality was estimated to be >98% after just 7 days of exposure. Complete mortality of eggs occurred after 14 days of cold storage. A 2 week treatment regimen may be sufficient for control of cowpea weevil in organic legumes. Technical Abstract: One California processor of organic garbanzo beans, unable to use chemical fumigants, relies on 30 days of storage at -18 degrees C to disinfest product of the cowpea weevil, Callosobruchus maculatus (F). To determine if the storage period may be shortened, the most cold tolerant life stage of the cowpea weevil was identified. Laboratory studies showed that the egg stage was most tolerant to -18 degrees C, and that adults were most susceptible. To examine the efficacy of cold storage disinfestation, bags of blackeyed peas infested with cowpea weevil eggs were buried within garbanzo bean bins placed in a commercial cold storage facility kept at about -18 degrees C and removed after 7, 14 and 21 days. Survival was highest in eggs located at the center of the bins, and coincided with the slowest cooling rate. Although temperatures within the bins did not reach -18 degrees C until after 14-19 days, egg mortality was estimated to be >98% after just 7 days of exposure. Complete mortality of eggs occurred after 14 days of cold storage. A 2 week treatment regimen may be sufficient for control of cowpea weevil in organic legumes. |
