Insecticidal Activity of Plant Powders against Rice Weevil

Abstract

Laboratory studies were conducted to study the effect of five leaf powders viz. Justicia adhatda (Adathodai), Azadirachta indica (Neem), Carica papaya (Papaya), Ocimum tenuiflorum (Tulsi) and Annona squamosa (Annona) on rice weevil Sitophilus oryzae L. infested rice in storage. The experiment was laid out in a completely randomized design (CRD) with five replications. Five grams of each plant powder were used to treat 100 g of rice grains. A control treatment having no any botanical was set up to compare the results in order to choose effective plant powder to control the rice weevil in storage. Six pairs of rice weevils were introduced to each treatment. The cumulative mortality percentage of adult weevil in different botanical treatments was recorded at two weeks interval. It was revealed that the use of powders from the selected indigenous botanical plants increased adult mortality of the rice weevils. Annona leaf powder recorded 100% mortality of the weevils at 10th week after the treatment and showed significantly (p<0.05) highest efficacy in controlling the adult weevils among the botanicals tested. Furthermore, Annona was followed by Tulsi to kill the weevils effectively in rice storage. Moreover, Adathodai had no significant (p=0.05) influence on the mortality of rice weevils. Therefore, the resource poor farmers can use ground botanicals namely, Annona and Tulsi in controlling rice weevils as they may not afford to buy chemical pesticides due to high cost.
Keywords: Botanical insecticides; Insect mortality; Rice weevil; Storage pest