Effect of Host Plants on the Potential of Aschersonia aleyrodis for Controlling Bemisia tabaci

The contact responses of egg parasitoid Trichogrammatoidea bactrae Nagaraja to the kairomones of its host diamondback moth(DBM),Plutella xylotella were bioassayed in laboratory.The attractive effect of 13 hydrocarbons,viz.pentadecane,hexadecane,heptadecane,nonadecane,2,6,10,14-tetramethyl pentadecane,heneicosane,docosane,pentacosane,heptacosane,octacosane,triacontane,pentatriacontane,hexatriacontane on T.bactrae were carried out.The results showed that the total exposure frequency of T.bactrae to the eggs cards treated with heptacosane was 74.71,the highest of all,and the highest parasitism of 53.83% was observed in the eggs cards treated with 2 000 ng/cm2 of heptacosane,which indicated the eggs cards treated with heptacosane was the most attractive to T.bactrae.In contrast,the eggs cards treated with hexadecane showed the weakest attractive to T.bactrae,and the total exposure frequency of T.bactrae against them was only 7,the least of all,and the lowest parasitism as 0.67% of T.bactrae was also observed in the eggs cards treated with the hexadecane.The parasitism of T.bactrae over 20% was found in the eggs cards treated with 2,6,10,14-tetramethyl pentadecane,pentacosane,heptacosane and hexatriacontane,and the parasitism under 5% was found in the eggs cards treated with hexadecane and docosane.In conclusion,the parasitoid T.bactrae showed the higher exposure frequency and parasitism in the eggs cards treated with hydrocarbons concentration between the concentrations 0.2 and 2×103 ng/cm2.