Bioefficacy and Economic Evaluation of Selected Insecticides against Lablab Bug, Coptosoma cribraria Fabricius in Dolichos Bean (Lablab purpureus (L.) Sweet)

Abstract

Dolichos bean (Lablab purpureus (L.) Sweet) is an important pulse-cum-vegetable crop cultivated extensively in India, and the pod-sucking bug, Coptosoma cribraria Fabricius, is a major field constraint. A field experiment was conducted during kharif 2015-16 and 2016-17 at the Horticultural Garden, College of Agriculture, Rajendranagar, Hyderabad, Telangana, to evaluate the bioefficacy and economic returns of selected insecticides against C. cribraria. The experiment was laid out in a randomised block design with nine treatments and three replications. Eight insecticidal treatments and an untreated control were evaluated, and three foliar sprays were applied at 10-day intervals beginning at 50 per cent flowering. Observations were recorded at 1, 3, 5 and 7 days after spraying, and pooled analyses were used to assess pest suppression, green pod yield and incremental cost-benefit ratio (ICBR). During the first spray, profenophos 50 EC @ 400 g a.i. ha-1 recorded the highest reduction of C. cribraria over the control, with 70.97, 77.03, 86.20 and 75.22 per cent reductions at 1, 3, 5 and 7 days after spraying, respectively. Beta-cyfluthrin + imidacloprid 300 OD @ 30 g a.i. ha-1 and imidacloprid 17.8 SL @ 25 g a.i. ha-1 were the next effective treatments. The highest pooled green pod yield was obtained with flubendiamide 480 SC (3316.0 kg ha-1), followed by chlorantraniliprole 20 SC (3101.5 kg ha-1) and profenophos 50 EC (2826.5 kg ha-1), compared with 1060.5 kg ha-1 in the untreated control. Profenophos 50 EC recorded the highest ICBR (1:13.72), followed by lambda-cyhalothrin 5 SC (1:7.61). The findings indicate that profenophos 50 EC was effective and economically advantageous for managing C. cribraria in Dolichos bean under the study conditions.