Study on characteristics of hyperparasitic parasitism on aphid parasites in different tobacco plant positions

Aphidius gifuensis is the main parasite enemy of tobacco aphid.However,the manipulative effect of A.gifuensis to aphid is greatly influenced by hyperparasitoid.Tobacco plants were divided into upper position,middle position,and lower position after topping.The hyperparasite rate of A.gifuensis to tobacco aphid at different positions,parasitism activities,and regularity of hyperparasitoids were preliminary studied.Results showed that the hyperparasitic rates in lower tobacco plant position were higher than that in the middle and the upper position at the beginning of tobacco growth.In the middle and late period,the hyperparasitic rate in the tobacco field was up to 40 percent,and the hyperparasitic rate in the middle and upper positions were remarkbaly higher.There were two kinds of hyperparasitoids in Xiangyun tobacco district of Dali,which were Pachyneuron aphidis(Bouche) and Phaenoglyphis sp.P.aphidis was the dominant species,and Phaenoglyphis sp in Yunnan have not yet been reported.The hyperparasitic rate in tobacco field reached its peak in early August.