Abstract
The rice weevil Sitophilus oryzae (L.) (Coleoptera: Curculionidae), is an important pest of stored grains throughout the world. Different biopesticides and synthetic insecticides have been used for a long time to minimize the rice weevil infestation but their efficacy is not satisfactory yet. The climate and storage conditions are highly favorable for quick progeny which may be responsible for lower efficiency of insecticides and higher level of infestation. Insect growth regulators (IGRs) like buprofezin are the semi-synthetic insecticides, mimic the insectproduced hormones and don’t kill the insects directly but reduces pest populations by affecting mating behavior, reproduction, egg viability, pre and post embryonic development etc. Laboratory experiments were conducted from August to November 2012, to evaluate the efficacy of buprofezin on the mortality and the suppression of progeny production of rice weevil. Ten adult rice weevils were exposed on three types of rice grains (long, medium and short) treated with buprofezin at 100, 200 and 300 ppm. Mortality was counted at 15, 21 and 28 days after treatment while adult progeny was counted at 6, 7 and 8 weeks after buprofezin treatment to get a new generation. The data showed that buprofezin had no direct effect on the mortality of rice weevils regardless the concentrations. Buprofezin at 300 ppm in rice grains significantly inhibited progeny production while lower doses (200 and 100 ppm) had no significant effect but virtually reduces progeny number. Types of grains were not factor for increasing or decreasing the rice weevils populations. In conclusion, buprofezin caused decreasing progeny productivity by S. oryzae (L.) with increasing concentrations regardless the types of rice grains.
Highlights
Stored grain pests are a great problem in Bangladesh and about 5-8% of the food grains, seeds and different stored products are lost annually due to stored pests infestation [1]
Data clearly showed that buprofezin had no significant effect on the mortality of adult rice weevil in comparison with that in the control
Compared to the control the mean mortality level was gradually increased with the increase of concentration while the highest mortality was recorded from 300 ppm for all grain types but the differences were not significant between control and buprofezintreated rice grains
Summary
Stored grain pests are a great problem in Bangladesh and about 5-8% of the food grains, seeds and different stored products are lost annually due to stored pests infestation [1]. About 13 species of insects have been recorded from Bangladesh which loss about 15% of stored rice [2]. Rice weevil, Sitophilus Oryzae (L.) (Coleoptera: Curculionidae) that is widely distributed, is one of the most destructive insect pests which cause severe economic loss. Rice weevils can cause losses to grain in storage, either directly through consumption of the grain or indirectly by producing ‘hot spots’ causing loss of moisture and thereby making grain more suitable for their pests [3]. The effective control of this insect has long been the goals of entomologists [4]. Storage with debris, poor sanitation and inappropriate storage facilities encourage insect attack. In tropical countries like Bangladesh, the climate and storage conditions are highly favorable for insect growth and development [5]
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