Population dynamics of Micraspis discolor (Coleoptera: Coccinellidae) in rice and its susceptibility to insecticides [in Bangladesh]
1991
Rahman, M.H. | Sardar, M.A. | Hoque, M.R.
Population density of the coccinellid beetle, Micraspis discolor (Fabricius) on rice in boro (Nov-May), aus (March- August) and aman (July-December) seasons, as well as toxic effects of malathion and dichlorvos on this predator were studied. Increasing number of M. discolor was noticed at the flowering stage of rice and adults were more numerous than larvae. M. discolor was more abundant in aus season that in the other two seasons of rice. In this season, population peaked in the last week of June on variety BR21 (Nizami) and second week of July on BR1 (Chandina). Among the different varieties of rice, lowest population density occurred on local variety (Nizarshail) during aman season. The feeding of larvae and adults on the pollen grains of newly emerged panicles indicated that M. discolor might choose rice ears as alternate food source. Malathion and dichlorvos sprays in field cages with released M. discolor on BR1 rice at flowering stage during aus season showed an equal toxicity, killing 100, 60-63 and 53% of adults at 0.075, 0.050 and 0.025% a.i. respectively.
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