Abstract:

The egg parasitoids Trichogrammatoidea bactrae Nagaraja and Trichogramma confusum Viggiani are potential biological control agents for the diamondback moth (DBM), Plutella xylostella (L.). In this study, the olfactory response of two parasitoids to saturated hydrocarbons from host egg shells and adult scales of P. xylostella were measured using a Y-tube olfactometer. The results indicated that the percentages of mated females of T. bactrae entering the treatment arms of 2,6,10,14-tetramethyl-pentadecane, pentadecane and heptadecane were 80.65%, 68.75% and 66.67%, respectively, significantly higher than those entering the control arms, suggesting that these three compounds could stimulate an intensive search behavior by T. bactrae. However, the parasitoid did not respond to other 10 hydrocarbons. The percentages of mated females of T. confusum entering the treatment arms of 2,6,10,14-tetramethyl-pentadecane, pentatriacontane and pentadecane were 84.38%, 70% and 62.16%, respectively, significantly higher than those entering the control arms, revealing that T. confusum were significantly attracted by those three compounds. While the numbers of T. confusum entering the treatment and control areas had no differences in the tests with other 10 hydrocarbons. In the case of unmated males of T. bactrae and T. confusum, there was no significant difference in entering numbers of wasps between the treatment and control arms for all 13 saturated hydrocarbons.

Key words: Trichogrammatids, Trichogrammatoidea bactrae, Trichogramma confusum, Plutella xylotella, kairomones, olfactory response