Cotton aphids very commonly damaged Lagerstroemia speciosa trees in the Southeast of Vietnam. Specially aphids could damage seedlings in the nursery
the leaves become curved, economic value is lost, therefore the plan for seedling propagation could be fail. A female A. gossypii has in total 37 - 47 nymphs, and 3.62 - 3.83 nymphs per day. There were four nymphal instars, the first instar lasted 1.07 - 1.14 days, the second lasted 1.03 - 1.09 days, the third lasted 1.25 -1.31 days, the fourth lasted 1.36 - 1.40 days, before producing offsprings it lasted 0.42 - 0.46 day, adult longevity lasted 7.67 - 8.83 days and the life cicle lasted 5.13 - 5.37 days on average. On tials of chemical and biological insecticides showed that Abamectin 0.004 percent, Bementent 0.166 percent, PSO 0.5 percent, Rotenone 0.02 percent, Thiamethoxam 0.0031 percent controlled the cotton aphid A. gossypii well.