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 (20 and 25 ± 2 oC), 70 ± 5 % R.H. and a photoperiod of 14 L: 10D. The life cycle of A. illinoisensis attained 14.7 and 7.1 days at 20 and 25 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 20 and 25 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 26% and 12.5 % of parasitoid eggs were encapsulated, while 52% of aphids were parasitized by A. albipodus of which 32 % 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.