Effect of insecticides sprays on the field population of predators in okra crop

Abstract

Pre-mix insecticide fipronil 4% + acetamiprid 4% SC (750, 1000, 1250 ml ha−1) and three other insecticides viz. emamectin benzoate 5% SG (170 g ha−1), acetamiprid 20% SP (75 g ha−1), pyriproxyfen 5% + fenpropathrin 15% EC (750 ml ha−1) were evaluated for combating pests in okra crop and effect on predators. These insecticides were sprayed twice at 10 days interval. The investigation results showed that predators’ populations decreased sharply after one day of each spray and increased gradually afterwards in subsequent days. However, populations in the sprayed plots at 10 DAS1 (Days after first spray) and 10 DAS2 (Days after second spray) were consistently less than the unsprayed control plots. Sprays of fipronil 4% + acetamiprid 4% SC (750 ml ha−1) caused minimum reduction in predators’ population at 10 DAS2 over pre-treatment (30.28%) and unsprayed control (50.60%) followed by pyriproxyfen 5% + fenpropathrin 15% EC (750 ml ha−1) with respective reductions of 35.56, 55.67% over pre-treatment and unsprayed control, respectively. On the other hand, sprays of fipronil 4% + acetamiprid 4% SC (1000, 1250 ml ha−1), emamectin benzoate 5% SG (170 g ha−1), acetamiprid 20% SP (75 g ha−1) caused 45.07 -49.62 and 55.74 -65.99% reductions in predators’ populations over pre-treatment and unsprayed control, respectively during the same time. In the mean time, the unsprayed control plots recorded overall 74.54% higher population of predators at 10 DAS2 over pre-treatment. By and large, amongst evaluated insecticides, fipronil 4% + acetamiprid 4% SC (750 ml ha−1) and pyriproxyfen 5% + fenpropathrin 15% EC (750 ml ha−1) appeared to be comparatively safer to prevalent predators in okra crop.