Effect of paddy variety, milling status and aeration on the progeny emergence of Sitophilus oryzae L. (Coleoptera: Curculionidae)

Abstract

In Sri Lanka, insects cause enormous losses in stored paddy; the rice weevil Sitophilus oryzae is a devastating insect. The magnitude of losses in stored paddy caused by insects varies with characteristics of paddy but has not yet been fully investigated. Due to the increased concerns on the use of synthetic chemicals, safer alternative pest management strategies for stored paddy are needed. Objectives of this study were to determine the effect of paddy variety, milling status and nature of aeration on the progeny emergence of S. oryzae. The experimental design was a three-factor factorial, completely randomized design (CRD).Freshly emerged S. oryzae adults were introduced to un-milled paddy or milled/polished rice belonging to traditional and improved varieties. The samples were maintained either open or airtight, and the progeny adults emerged was determined at monthly intervals. Progeny emergence was lower in the traditional varieties, un-milled paddy and under air-tight condition compared to improved varieties, milled/polished rice and aerated samples, respectively. Overall, the improved variety Bg 300 exhibited the maximum resistance to infestation by S. oryzae. Furthermore, white-colour and long-grain varieties produced lower progeny of S. oryzae than red-colour and short-grain varieties, respectively. It is concluded that the maximum protection in paddy/rice from insect infestation during storage can be achieved by using traditional varieties, stored as un-milled paddy (without dehusked) under airtight condition.