ABSTRACT
Trichogramma chilonis, an egg parasitoid that is being augmentatively released against various sugarcane borers in Pakistan, failed to significantly parasitize sugarcane top borer, Scirpophaga nivella, which has a thick covering of scales on its egg masses. A scelionid wasp Telenomus dignus was found parasitizing the pest eggs but not providing effective control. However, female wasps disturbed the scales layer on the egg masses, facilitating Trichogramma parasitism. Field observations were made on parasitism and pest population levels where releases of each parasitoid species were made separately and where both T. chilonis & T. dignus were combined. The results were compared with the control where no releases were made. A significant reduction in pest population occurred in the fields with augmentation of both parasitoids. Parasitism remained less than 1% throughout the year in the control. Parasitism by T. chilonis increase in the fields where it was released with T. dignus, and reached a peak of 37% in September, compared with maximum 4% parasitism in the field where it was released alone. Results of laboratory studies supported the field trials.
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