Evaluation of corn leaf aphid (Rhopalosiphum maidis; Homoptera: Aphididae) honeydew as a food source for the egg parasitoid Trichogramma ostriniae (Hymenoptera: Trichogrammatidae)

The effect of honeydew produced by the corn leaf aphid, Rhopalosiphum maidis (Homoptera: Aphididae), on the longevity and parasitism performance of the egg parasitoid Trichogramma ostriniae (Hymenoptera: Trichogrammatidae) was evaluated in a series of experiments conducted on corn (Zea mays) plants under controlled laboratory conditions. Wasps confined in bioassay cages on corn leaves with either honey or aphids survived on average 212.0 h and 206.7 h, respectively, which was significantly greater than the mean survival of wasps confined with only a corn leaf (29.1 h) or with nothing (28.5 h). To measure parasitism, wasp cohorts comprising one male and four females were confined on corn leaves either with or without aphids, and allowed to parasitize eggs of the European corn borer, Ostrinia nubilalis (Lepidoptera: Crambidae). Wasps with access to aphid honeydew parasitized significantly more egg masses per day and a significantly higher proportion of eggs within each mass than wasps confined with only corn leaves. The total number of progeny produced by each wasp cohort per day and the proportion of progeny that were female were also significantly higher for the wasps provided with honeydew. Feeding treatment had no effect on the number of progeny emerging from each parasitized egg. We conclude that aphid honeydew has the potential to be an important within-field food resource that may impact the success of augmentative control of O. nubilalis by T. ostriniae released into cornfields.