Defense reactions of the grape aphid, Aphis illinoisensis (Hemiptera: Aphididae) to parasitoid species Lysiphlebus testaceipes (Hymenoptera: Braconidae) and Aphelinus albipodus (Hymenoptera: Aphelinidae)

Developmental periodsof thegrapevine aphid, Aphis illinoisensis Shimer (Hemiptera: Aphididae) on the grape, Vitis vinifera L., and its two parasitoid species, Lysiphlebus testaceipes (Cresson) (exotic) (Hymenoptera: Braconidae: Aphidiinae) and Aphelinus albipodus Hayat and Fatima (indigenous) (Hymenoptera: Aphelinidae) were studied at two constant temperatures (۲۰ and ۲۵ ± ۲ oC), ۷۰ ± ۵ % R.H. and a photoperiod of ۱۴ L: ۱۰D. The life cycle of A. illinoisensis attained ۱۴.۷ and ۷.۱ days at ۲۰ and ۲۵ oC, respectively. The developmental period was shorter as temperature increased. Developmental time from egg to adult of L. testaceipes was shorter than that of A. albipodus Hayat and Fatima at both ۲۰ and ۲۵ oC. Parasitized aphids were dissected daily to determine the percentage of parasitim, number of encapsulated eggs of L. testaceipes and the number of dead larvae of A. albipodus. The percentage of parasitism of aphid by L. testaceipes was ۲۶% and ۱۲.۵% of parasitoid eggs were encapsulated, while ۵۲% of aphids were parasitized by A. albipodus of which ۳۲ % was dead larvae. Therefore, A. illinoisensis has a mechanism for defense against parasitoids and it should be noted that this aphid is not a suitable host for rearing either of the two tested aphid parasitoid species in the laboratory.

Keywords:

Aphis illinoisensis , Aphelinus albipodus , Lysiphlebus testaceipes , developmental period , Defense