Damage Potential, Effect on Germination, and Development of Sitophilus oryzae (Coleoptera: Curculionidae) on Wheat Grains in Northwestern Himalayas.

The present investigation was carried out to study the biological parameters and orientation of Sitophilus oryzae (L.) toward wheat cultivar HPW-236 and mixed grains of different cultivars (HPW-155, HPW-236, HPW-249, HPW-349, HPW-360, HS-490, and VL-892). The incubation period, larval period, pupal period, and total life cycle period of S. oryzae was longer when fed on mixed grains as compared to HPW-236. Also, the weevils were more oriented toward HPW-236 and lower germination rates were observed from HPW-236 than mixed cultivars when exposed to S. oryzae. We also evaluated quantitative losses caused by S. oryzae in different cultivars of wheat recommended in the northwestern Himalayas under free-choice conditions. The weevil inflicted greater damage and weight loss in grains of HPW-236 while it was negligible in the case of HPW-360 and HPW-249. HPW-236 which is the most cultivated variety of wheat in northwestern Himalayas proved to be highly susceptible to the weevil and provided a more suitable environment for weevil's development. Therefore, this particular cultivar can be avoided for prolong storage and the farmers should prefer cultivars such as HPW-360 and HPW-249, which proved to be least affected the weevil.

Influence of Different Plant Powders as Grain Protectants on Sitophilus oryzae (L.) (Coleoptera: Curculionidae) in Stored Wheat.

ABSTRACT: Sitophilus oryzae (L.) is the most widespread and destructive insect of stored wheat throughout the world. The main aim of the study was to find ecofriendly alternatives to chemical fumigants and synthetic insecticides for the control of weevils in stored wheat. The leaf powder of Ageratum conyzoides proved to be the best treatment against the weevil that resulted in maximum mean cumulative mortality (96.67%), the lowest monthly population increase (18.33), and the least grain damage (12.61%) and weight loss (1.75%) during 6 months of storage. The next best treatments were the drupe powder of Melia azedarach, followed by Vitex negundo and Ocimum sanctum. A. conyzoides, Melia azedarach, and O. sanctum were found effective even 3 months after preparation. The leaf powder of Murraya koenigii resulted into the lowest mean cumulative adult mortality (14.23%), the highest monthly population increase (132.78), and the highest grain damage (47.50%) and weight loss (11.07%), thus proving to be the least effective.