EFFECTIVENESS OF NEWER CHEMISTRY INSECTICIDES AGAINST CITRUS LEAFMINER (Phyllocnistis citrella) INFESTING JARA LEMON IN SYLHET REGION

Abstract

The study on the effectiveness of newer chemistry insecticides against Citrus leafminer (Phyllocnistis citrella) was conducted in the farmer’s Jara lemon field at Bagerkhal under Fatehpur Union, Jaintapur Upazilla, Sylhet during January to August, 2016. The insecticide treatments were imidacloprid (Sapta 70 WG) (T1) applied at 0.5 g L-1 of water, bioneem plus (Azadirachtin 1 EC) (T2) applied at 1 ml L-1 of water, spinosad (Tracer 45 SC) (T3) applied at 1.25 ml L-1 of water, chlorfenapyr (Intrepid 10 SC) (T4) applied at 1 ml L-1 of water and untreated control (T5) with four replications. The treatments were randomly assigned to each replication and applied at 20-day intervals. Data of leaf infestation were collected from four canopies of one tagged plant. Each of four canopies was selected respectively from north, east, west and south direction of the tagged plant. The numbers of infested leaves were counted at 20-day intervals. The infestation rate was calculated from the mean data of four replicates for each treatment. The results revealed that highest leaf infestation reduction (22%) was obtained from the plant treated with bioneem plus (Azadirachtin 1 EC) (T2) followed by spinosad (Tracer 45 SC) (T3) (29.25%). The results indicate that bioneem plus and spinosad are most effective for the management of leafminer infesting Jara lemon. Bioneem plus treated plants offered highest fruit yield of Jara lemon (1.82 t ha-1), closely followed by spinosad (1.71 t ha-1). As regard to economic analysis, the highest Marginal Benefit Cost Ratio (MBCR) (9.55) was obtained from the treatment bioneem plus (T2), closely followed by spinosad (T3) (8.21). Based on crop protection level and economic returns, bioneem plus and spinosad may be recommended for the management of leafminer in Jara lemon.