Benefit-cost ratio evaluation for management of Brevicoryne brassicae L. in canola (Brassica napus L.) crop production

Canola is an important oilseed crop. It is attacked by different insect pests. Cabbage aphid (Brevicoryne brassicae L.) is one the most destructive sucking insect pests of this crop. Its infestation affects the yield and quality of seed. Three different levels of nitrogen fertilizers, i.e., 120, 60 and 30 kg/hac, two environmentally safe insecticides i.e., emamectin benzoate and imidacloprid at three different application intervals i.e., 4, 8 and 12 days after first application (DAFA) were tested for management of cabbage aphid in canola. The experiment was laid out in a sub-sub plot design keeping nitrogen fertilizer levels as main plot, insecticides as sub plot and insecticide application intervals as sub-sub plots. Number of aphids per plant and canola seed yield for each combination was recorded. Total expenses from crop production till harvest were calculated on market rates of 2019. Benefit-cost ratio for each treatment combination was calculated. Lowest aphid infestation was fond for 4DAFA. Highest benefit-cost ratio (2.57) was recorded for imidacloprid applied at 4DAFA with 120 kg/ha nitrogen fertilizer. But for the management of cabbage aphid in environment friendly manner we recommend emamectin benzoate at 8DAFA with nitrogen level of 60 kg/hac giving slightly lower BCR (2.37).