Application of olfactory response of natural enemies for species selection in biological control: a comparative study on Trichogramma evanescens West. and T. brassicae Bezd.

The olfactory responses and biological attributes of Trichogramma evanescens (Te) and T. brassicae (Tb) were studied at laboratory conditions. Odor treatments included Carob moth eggs and healthy and infested pomegranate crown and seed and healthy and artificially damaged leaves. The olfactory apparatus consisted of a Y shape glass tube with 30° angle. Ninety mated females (0–24 hrs. old) of each species were exposed to the selected odor and clean air in 3 replications (each 30 wasps as one replication). In addition, biological characteristics of wasps were determined on Carob moth eggs using two sex age–staged life table approach. Olfactory results revealed that Te wasps significantly responded to the odors of Carob moth eggs and healthy and infested pomegranate crown and seed over clean air. In contrary, Tb wasps did not respond positively toward any tested odor. Considering biological trait investigations, Te male and female immature stage took 10.70 and 10.52 days being significantly shorter compared with that of Tb male (11.20 days) and female (10.95 days), respectively. Adult female Te had 3 days longevity which was one day longer than that of Tb wasps (2 days). The net reproductive rate and intrinsic rate of population increase of Te and Tb wasps were 16.56 offspring and 0.2337 day–1 and 15.20 offspring and 0.2220 day–1, respectively. Eventually, the transformation rate of host to parasitoid egg (Qp) was equal to 1 for both species. In order to select superior natural enemy candidates for biological control programs, the possibility of using fast olfactory tests instead of time consuming biological studies is discussed.