KBTT Wijerathne, DMSK Dissanayaka and LKW Wijayaratne*
Department of Plant Sciences, Faculty of Agriculture, Rajarata University of Sri Lanka, Puliyankulama, Anuradhapura, Sri Lanka
Abstract
Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) and Sitophilus oryzae (L.) (Coleoptera: Curculionidae) are serious pests of stored food. Exposure to high or low temperatures is effective in controlling these two species but accompany limitations. Spinosad, derived from bacterium Saccharopolyspora spinosa, is an effective insecticide but synergistic effect on heat- or cold-acclimated insects has not been reported. The objectives of this study were to determine if spinosad affects the mortality of T. castaneum and S. oryzae adults under temperature acclimated and unacclimated conditions. Adult insects were exposed to spinosad or water, acclimated at 35 0C and 40 0C, and finally held at 45 0C for 0-30 h for T. castaneum and 0-12 h for S. oryzae. The mortality of adults at different
durations was recorded and LT50 values were calculated. Exposure to spinosad before heat exposure reduced the
heat tolerance of T. castaneum and S. oryzae adults. Acclimation at intermediate temperatures 35 0C and 40 0C increased the heat tolerance of both S. oryzae and T. castaneum adults. Further study is needed to determine the
effect of spinosad on the heat tolerance and heat acclimation of other stored-product insect species.
Key words:
Heat acclimation, Heat tolerance, LT50, Spinosad, Stored-product insects
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* - Corresponding Author
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