Evaluation of novel insecticides against diamondback moth and natural enemies in cabbage ecosystem

Aim: Insect pest infestation is the major limiting factors for commercial cultivation of cabbage. Diamondback moth (DBM) is the most notorious insect pest responsible for yield loss of cabbage in most of the cases. The objective of the present study was to evaluate some new insecticides having different novel mode of action against this pest. Methodology: Field experiments were conducted at C-Block Farm, Bidhan Chandra Krishi Viswavidyalaya (BCKV), West Bengal, India during 2011-12 to 2013-14. The field experiments were laid out in randomized block design comprising eight treatments including control with three replications. The treatments viz. pyridalyl 10 EC, indoxacarb 14.5 SC, chlorfenapyr 10 SC and chlorpyriphos 20 EC were applied twice at fifteen days interval. Pre-treatment counts of DBM larvae were recorded from randomly selected 5 tagged plants/plot, and subsequently post treatment observations were recorded on 1, 7 and 14 days after each spraying. Coccinellid complex and spiders were recorded during each observation after spraying. Healthy cabbages (weight basis) were recorded separately from each replication for yield data.Results: Chlorrenapyr @ 200 g a.i. ha(-1) was effective in reducing mean larval population of diamondback moth (1.21 larvae per plant) with 85.81 % reduction over untreated control. Next best treatment was yridalyl @ 150 g a.i ha(-1) with 82.71% reduction followed by indoxacarb @ 150 g a.i. ha(-1) (78.44% reduction). Recommended doses of pyridalyl (75 g a.i. indoxacarb (75 g a.i. ha(-1)) and chlorfenapyr (100 g a.i. ha(-1)) were also found to be effective treatments in reducing the larval population of diamondback moth. Highest cost-benefit ratio (1:10.94) was recorded in pyridalyl at recommended dose (75 g a.i. ha(-1)) followed by chlorpyriphos 250 g Interpretation: Chlorfenapyr, pyridalyl and indoxacrb were found to be effective insecticides against diamondback moth. Pyridalyl and indoxacarb were found to be relatively safe insecticides towards coccinellid beetles and spider population in cabbage ecosystem. [GRAPHICS] .