Effect of application time of insecticides on cabbage aphid, Brevicoryne brassicae population and yield of canola crop

Canola is an important oilseed crop in the world. Cabbage aphid, Brevicoryne brassicae is one of the most important pests of canola crop in Iran. In this study, the effect of chemical control of cabbage aphid was investigated in autumn and spring on Hyola 401 cultivar. For this purpose, spring and autumn sprayings with imidacloprid and pirimicarb at 1/1000 concentrations and insecticidal soap at 2.5% concentration were assessed using a randomized complete block design. The experiments were conducted during two growing seasons, 2011 and 2012 in Qazvin province. The results showed that, both autumn and spring spraying is necessary for pest control. Autumn and spring sprayings with imidacloprid caused 99.5 ± 0.4%, 94.5 ± 2.4% and 95.4.1 ± 1.0% mortality in 2011 and 99.1 ± 0.5, 86.9 ± 2.7 and 93.1 ± 5.5% mortality in 2012, three, seven and 15 days after treatment, respectively. Highest yield achieved at imidacloprid treatment and was 3533.00 kg/ ha. If not controlled, the damage would be 66.18, 69.35 and 78.0% at spring, autumn and spring-autumn treated plots.