Management of whitefly, Bemisia tabaci (Gennadius) in bushy Lac host, Flemingia semialata at Thrissur, Kerala

Abstract

Flemingia semialata is an established host plant of lac insects and is widely grown to promote lac cultivation in India. One of the most destructive pests that can cause significant yield loss in many crops is a sap sucking whitefly, Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae), which is also found to infest the Flemingia sp. They cause vast damage to the host plants during feeding by reducing the rate of photosynthesis through the excretion of honeydew and by transmitting a large number of plant pathogenic viruses. Although there are several methods to control whitefly infestation, the commonly adopted practice is the application of chemical pesticides, owing to their efficiency in whitefly control. This study focused to test the effectiveness of two chemical: Thiamethoxam 25% WG (Actara®) and Phosmet 70 % WP (Imidan®) and an organic pesticide: Neem Oil, in whitefly control on F. semialata. The experimental design consisted of two different concentrations of each pesticide i.e., Phosmet 0.5 ml/L, 1ml/L, Thiamethoxam 0.25g/L, 0.5 g/L, Neem oil 1ml/L, 2ml/L applied on 21 test plants in sets of three and also on three regions of the test plants i.e, upper, middle and lower. The number of whiteflies was counted after 6, 12 and 24 hours of pesticide application. The results revealed that, among all the treatments, Thiamethoxam 0.5mg/L was found to be the most effective with highest percentage of reduction over control in the number of whiteflies in all the time intervals. The leaves in the middle and lower regions of the test plants showed relatively higher loads of whiteflies than those in the upper region throughout the experiment. Although, Neem oil is an environment friendly natural pesticide, Thiamethoxan has negligible volatilization properties and high degradation rates in the soil and therefore could be successfully and safely applied on the lac insect host plants during the pre-inoculation stages to lessen the whitefly attack.