NSECT PESTS OF LETTUCE AND THEIR BIORATIONAL MANAGEMENT

Abstract

The experiment was conducted in the experimental field of Sher-e-Bangla Agricultural University, Dhaka, Bangladesh during the period from 10 November, 2019 to 20 February, 2020 to record the insect pests of lettuce and to evaluate their biorational management practices. The experiment was laid out in Randomized Complete Block Design (RCBD) with four replications. There were six treatments viz.; T 1 = Abamectin @ 1.0 ml/L of water, T 2 = Bacillus thuringiensis and abamectin @ 1.0 ml/L of water, T 3 = Spinosad @ 0.5 ml/L of water, T 4 = Azadirachtin @ 1.0 ml/L of water, T 5 = Potassium salt of fatty acid @ 1.0 ml/L of water and T 6 = untreated control were used at 7 day interval. Flea beetle (Monolepta signata Olivier), Tobacco caterpillar (Spdoptera litura Fabricius), Aphid (Lipaphis erysimi Kaltenbach), Jute hairy caterpillar (Spilosoma obliqua Walker), Grasshopper (Oxya velox Fabricius) and Red pumpkin beetle (Raphidopalpa foveicollis Lucas) were recorded. The lowest percent of leaf infestation (10.70, 4.67, 4.76, 5.07, 5.03 and 8.74% respectively) of Flea beetle, Tobacco caterpillar, Aphid, Jute hairy caterpillar, Grasshopper and Red pumpkin beetle were observed in T 3 (Spinosad 45SC) treatments as against the highest (26.93, 18.81, 18.22, 37.67, 24.70 and 26.93%) was observed in T 6 treatment (untreated control). The highest single (0.91 kg plant ii

-1 ) and healthy plant weight (0.76 kg plant -1 ) and highest yield (16.43 ton ha -1 ) were observed in the same treatment (T 3 ). In contrast, the highest leaf infestation (21.50%), the lowest single plant weight (0.24 kg), healthy plant weight (0.29 kg plant -1 ) and lowest total yield (7.08 ton ha -1 ) were obtained from T 6

(untreated control). Spinosad 45SC @ 1.0 ml/L of water at 7 days interval gave the highest performance against insect pests of lettuce compared to all other treatments and may be used for the management insect pests of lettuce.