Effect of insecticide stress on physiological and biochemical indicators of Brassica campestris L.

The effect of four insecticides (Bacillus thuringiensis, Abamectin, Fipronil, and Beta-cypwrmethrin) on five principal physiological and biochemical indicators (chlorophyll, soluble sugar and free amino acid content, and SOD and POD activity) of B.campestris was researched. The results show that chlorophyll content declines compared with the control treatment 14 days after insecticide application. After three weeks of insecticide application, each treatment shows a significant difference in chlorophyll content in the order as follows: Fipronil treatment > Beta-cypwrmethrin treatment > Abamectin treatment > Bacillus thuringiensis treatment > control treatment. Soluble sugar content is relatively high after 7 days in Fipronil and Beta-cypwrmethrin respectively,while in Abamectin, is significant higher than that in other treatments 21 days after insecticide application. In comparison with the control treatment, THR, ILE and PHE contents are markedly high, while VAL and HIS contents are markedly low three weeks after insecticide application. On the whole, the effect of insecticide stress on free amino acids in the leaves of B.campestris relatively intensifies after 14 days with light Fipronil stress effect, but serious Beta-cypwrmethrin stress effect. Seven days after insecticide application, SOD activity in Abamectin treatment and BT treatment significant increases over that in other treatments. SOD activity is simply highest in Abmectin treatment after two weeks, while all treatments have less SOD activity than the control three weeks after application. POD activity rises on the average, and the range of increase in Fipronil treatment and Abamectin treatment is a little high, reaching 598% and 247% respectively. This study provides an important theoretical and practical basis for reasonable selection of insecticides to control B.campestris pests.