Document Type : Original Article
Authors
1
Department Plant Protection, Faculty of Agriculture, Sanaa University, Sanaa, Yemen
2
Department of Stored Product Pests, Plant Protection Research Institute, Agricultural Research Center, Sabahia, Alexandria, Egypt
3
Department of Pesticides Chemistry, Faculty of Agriculture, Alexandria University, 21545-El-Shatby, Alexandria, Egypt
10.21608/jpces.2009.459546
Abstract
A study was conducted to evaluate the efficacy of eight monoterpenes namely (-)-carvone, 1-8-cineole, cuminaldehyde, (L)-fenchone, geraniol, (-)-limonene, (-)-linalool and myrcene against two major stored-grain insects on wheat seeds in the laboratory. Insect species tested were the rice weevil, Sitophilus oryzae (L.), and the rust red flour beetle, Tribolium castaneum (Herbst). Wheat seeds were treated with monoterpenes at 0.5, 1 and 5 mg/g for controlling the two insect species. Out of the eight monoterpenes, (-)-carvone was the most toxic compound against both insects at the three tested application rates after one and two weeks of treatment. Geraniol and cuminaldehyde were among the most effective compounds against both insects. Four of the tested monoterpenes (carvone, cuminaldehyde, geraniol and (-)-linalool) caused complete mortality to the adults of S. oryzae after one week at the rate of 5mg/g, while all of the tested monoterpenes except myrcene and (-)-linalool caused complete mortality of T. castaneum adults at the same application rate. Comparing the toxicity of monoterpenes toward the two insects indicated that, (-)- limonene, (L)-fenchone and cuminaldehyde had approximately the same activity on both insects. On the other hand, myrcene, geraniol, (-)-carvone and 1-8-cineole were more toxic against T. castaneum than S. oryzae, while (-)-linalool was more toxic towards S. oryzae than T. castaneum. All of the tested compounds except for myrcene showed significant reduction in progeny production of S. oryzae after 6 and 12 weeks of treatment compared with control. (-)-Carvone was the most effective in reducing the progeny production at the three tested application rates, followed by geraniol, cuminaldehyde and (-)-linalool. These four monoterpenes provided complete suppression of progeny production at the rate of 5 mg/g after 12 weeks. At the rates of 1 and 5mg/g. the majority of monoterpenes significantly reduced weight loss of treated wheat and complete protection was observed in wheat treated with (-)-carvone, geraniol, cuminaldehyde and (-)-linalool at 5 mg/g. These strong insecticidal activities of monoterpenes particularly (-)-carvone, geraniol, cuminaldehyde and (-)-linalool indicate that these monoterpenes can used for control S. oryzae and T. castaneum in stored wheat.
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