Ovipositional preference of Trathala flavoorbitalis Cameron (Hymenoptera: Ichneumonidae), a larval parasitoid of eggplant fruit and shoot borer, Leucinodes orbonalis Guenee (Lepidoptera: Pyralidae), with notes on its biology
2009
Solleza, M.O., Philippines Univ. Los Baños, College, Laguna (Philippines). Crop Protection Cluster
The ovipositional preference of Trathala flavoorbitalis Cameron (Hymenoptera: Icheneumonidae) for eggplant fruit and shoot borer (EFSB) Leucinodes orbonalis Guenee larvae in four instars was determined in the laboratory. Given free choice, first and second instar larvae were not selected by T.flavoorbitalis for oviposition but host mutilation was apparent. Third and fourth instar larvae were more preferred. Females more readily oviposited in borer larvae with fresh fecal matter than on those with no fecal matter. No choice experiment resulted in high parasitism in both third and fourth instar larvae. Field parasitism in different sampling areas ranged from 16.70 to 25.88% with an average of 21.54%. Higher parasitism was recorded on eggplant borer larvae collected from the fruits (19.35%) as compared with larvae collected from the shoots (12.28%). Other larval parasitoids that emerged included a scelionid wasp and Cotesia sp. Cocoon of unparasitized larva was significantly bigger than that of parasitized larva. Laboratory results showed an average of 15.98% parasitism. T.flavoorbitalis is a larval parasitoid. Life cycle of Trathala from oviposition to successful parasitoid emergence was about 20-24 days. It undergoes three-larval instars. Adult longevity was shortened (2.82 + or - 0.85 days) when adult parasitoid was not provided with food. When fed with honey, Trathala adult lived for about 9.64 + or - 2.46 days. Multiple stinging is one of the characteristics of this insect. This however, does not necessarily lead to parasitoid development but can help reduce eggplant borer population. Successful parasitization on eggplant borer in the absence of male in the laboratory confirms that this parasitoid is a parthenogenetically thelytokous species. For the present study, Trathala is classified as thelytokous since significant number of collected parasitoids were all female. This parasitoid, being parthenogenetically thelytokous species with satisfactory levels of parasitism and can be reared in the laboratory, has good potential as a biological control agent against the eggplant fruit and shootborer.
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