BIORATIONAL MANAGEMENT OF MAJOR INSECT PESTS OF BLACKGRAM

Abstract

A field experiment was guided by RCBD trial with three replications during the period from September to November, 2019 at the Research Farm of Sher-e-Bangla Agricultural University (SAU), Dhaka to study the biorational management of major insect pests of blackgram. Blackgram variety BARI mash-3 (Hemantoo) was used as planting materials for the study. The experiment consists of seven treatments as T 1 = spinosad @0.5 ml/l of water at 10 days interval, T 2 =emamectin benzoate @1.0 ml/l of water at 10 days interval, T 3 = lufeneuron @0.2 g/l of water at 10 days interval, T 4 = matrine @1 ml/l of water at 10 days interval at, T 5 = thiamethoxam @0.5g /l of water at 10 days interval, T 6 = neem seed kernel @5 g/l of water at 10 days interval & T 7 = Untreated control. Major insect pests found were aphid, white fly, stemfly, stink bug, jassid, flea beetle and pod borer. The lowest number of aphid per plant (3.30) was found from T 1 , while the highest (16.53) from T 7 . The lowest number of whitefly per 10 leaves (4.03) was found from T 5 , whereas the highest (13.60) from T 7 . The lowest number of stemfly infestation per plant (2.10) was found from T 1 , while the highest (7.70) from T 7 . The lowest number of stink bug per plant (1.10) was found from T 1 , while the highest (4.33) from T 7 . The lowest number of jassid per 10 leaves (1.07) was found from T 1 , while the highest (4.33) from T 7 . The lowest number of flea beetle per plant (2.30) was found from T 1 , while the highest (9.40) from T 7 . The lowest number of flea beetle infested leaf (2.00) was found from T 1 ii , while the highest (9.90) from T 7 . At early pod development stage, the lowest infestation (2.59%) was recorded in T 1 treatment, whereas the highest infestation (15.60%) in T 7 treatment. At late pod development stage, the lowest infestation (3.31%) was recorded in T 1 treatment but the highest (14.19%) in T 7 treatment. The highest yield (1.84 ton/ha) was recorded in T 1 treatment, whereas the lowest (1.16 ton/ha) in T 7 treatment. The highest benefit cost ratio (2.31) was estimated for T 1 treatment, while the lowest (1.28) from T 4 treatment. Neem seed kernel @5 g/l of water at 10 days interval treatment was less effective against most of the insects in terms of number of insects and percent reduction of insect pests but it showed better performance than some of the chemical insecticide. It reduced 63.31% aphid, 33.7% whitefly,34.39% stemfly infestation, 14.26% stink bug, 75.30% jassid, 40.38% flea beetle, 44.67% flea beetle infested leaf, 18.38% pod borer infestation at early stage and 45.94% pod borer attack at late pod development stage. It was revealed that Spinosad @0.5 ml/l of water at 10 days interval was more effective against the major insect pests of blackgram.