Abstract:

The physiological and biochemical indexes of Malus micromalus and the biological parameters of Aphis citricola and its predator Harmonia axyridis were investigated after Abamectin, a pesticide treatments. The results showed: 1) Leaves from M. micromalus displayed lower leaf wax content, chlorophyll content and superoxide dismutase (SOD) activity, and higher total aminophenol content and soluble sugar content, compared with the control. The various trends of these indexes were showed as the pesticide concentration increased. 2) A. citricola, an aphid reared on leaves of M. micromalus after Abamectin treatments displayed significantly longer longveity and higher fecundity than those of the control . With increasing of the pesticide concentration, the longveity prolonged, while the fecundity decreased. 3) H. axyridis, who fed the aphids after 8 000 and 10 000 times Abamectin treatmeats had a significantly higher daily predacious number of the aphids, while those fed aphids after 4 000 times Abamectin treatment displayed lower daily predacious number , compared with the control. H. axyridis, who fed aphids after 4 000 and 8 000 times Abamectin treatments, were longer preoviposition period, whereas those fed aphids after 10 000 times Abamectin treatment were shorter preoviposition period, compared with the control. H. axyridis fed aphids after Abamectin treatments showed a significantly lower fecundity and incubation rate than those of the control. Our results indicated that Abamectin could affect A. citricola and its predator H. axyridis through the food chain.

Key words: Abamectin, Malus micromalus, Aphis citricola, Harmonia axyridis