Colonization of Six Exotic Parasites (Hymenoptera) Against Diatraea grandiosella (Lepidoptera: Pyralidae) in Corn

Abstract

Sixexotic parasites, Trichogramma atopavirilia Oatman & Platner, Allorhogas pyralophagus Marsh, Cotesia flavipes Cameron, Macrocentrus prolificus Wharton, Digonogastra kimballi Kirkland, and Pediobius furvus (Gahan), were colonized in commercial corn fields in the Texas High Plains against Diatraea grandiosella Dyar from 1985 to 1987. Colonization sites were monitored to estimate parasitization, dispersal, and parasite overwintering. D. kimballi , an external parasite of late instars, dispersed farther than other species and was the only parasite to demonstrate a propensity for overwintering. The pupal parasite, P. furvus , was capable of causing seasonal parasitization as high as 50.0% within 10 m of the colonization locus and showed the strongest numerical increase. The egg parasite, T. atopovirilia , caused 33.6% parasitization within 2 m of the colonization locus but was not recovered at greater distances. Parasitization by A. pyralophagus , which attacks medium sized larvae, never exceeded 3.6% in any year of the study. Seasonal parasitization of C. flavipes , a parasite of late instars, was 0.0–14.5%, but the potential of this parasite as an effective natural enemy of D. grandiosella is limited by apparent encapsulation in the hosts and inability to overwinter. The polyembryonic larval parasite, M. prolificus , was not recovered during the 3-yr study. An aggregative response to host density was not detected for any of the parasites. The results of this study suggest that D. kimballi may be able to establish in the Texas High Plains, and that P. furvus may have potential as a biological control agent in a seasonal inoculative or inundative approach.