Submitted to: Journal of Economic Entomology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 8/19/1999
Publication Date: 6/20/2000
Citation: Yokoyama, V.Y., Miller, G.T. 2000. Response of omnivorous leafroller (lepidoptera: tortricidae) and onion thrips (thysanoptera: thripidae) to low temperature storage. Journal of Economic Entomology. Volume(93):1031-1034. Interpretive Summary: Omnivorous leafroller is a pest of regulatory concern in California table grapes limiting exports to foreign markets where the insect is not found. Onion thrips is normally found as a field pest, but can cause damage and losses in onions stored after harvest. Low temperature storage has potential to control these postharvest pests in commodities that can be stored at about 0C for several weeks. The objective of this investigation was to evaluate the response of each pest to low temperature storage as an alternative to chemical pesticides. In laboratory tests a six week exposure to 0-1C caused 99.7% or greater mortality of omnivorous leafroller eggs and larvae. However, the immature stages of omnivorous leafroller that survived the exposure later developed to reproductive adults. The same low temperature treatment caused 99.8% mortality of onion thrips. The findings suggest that low temperature storage has potential to control both pests for quarantine and postharvest purposes. The effectiveness of the treatment may be enhanced by combining other control techniques in the field and packinghouse to further lower the pest populations to levels that are acceptable to either importing countries or producers and consumers.
Technical Abstract: Mean percentage survival to the adult stage of omnivorous leafroller, Playnota stultana Walshingham, eggs and 1st-5th instars was 60.7-95.2% for non-exposed immatures and 14.5-54.3% for immatures exposed to 1 wk at 0-1C Two to 5 wk exposures resulted in 0.6-7% survival and a 6 wk exposure caused <1% survival of all stages tested. A significant reduction in survival occurred between 0 and 1 wk and between 1 wk and 2-6 wk exposures for all larval stages. Survival of eggs after 0 to 1 wk exposures was significantly differed than survival after 2-6 wk exposures. The 2nd instar was the least susceptible stage to low temperature storage. Adults that were exposed to low temperature for 1 wk in the 3rd through 5th instars laid a mean of 120-289 eggs per female and the mean percentage viability of the eggs ranged from 56.2 to 71.4%. Mean percentage survival of onion thrips, Thrips tabaci Lindeman, adults and nymphs was inversely related to the duration of exposure from 1 through 3-6 wks at 0.1 and 5C and was lower at 0-1 (0.2-52.5%) than 5C (17.6-66.6%). Exposure to 0-1C for 4 wk attained 91.2% control which increased to 99.8% after 6 wks. Low temperature storage has potential to control omnivorous leafroller in table grapes, Vitis vinifera L., and onion thrips in onions, Allium cepa L.