Helicoverpa zea (Lepidoptera: Noctuidae) Dynamics and Parasitism in Maryland Soybeans

Abstract

Larval populations of the corn earworm, Helicoverpa zea (Boddie), were surveyed in soybeans from 1995 to 1997 to catalogue larval parasites and quantify rates of parasitism. In addition, the relationship between moth captures in black-light traps and larval densities in soybeans was examined. Parasitism was consistently high throughout the region averaging 80.3, 82.3, and 73.1 for all dates in 1995, 1996, and 1997, respectively, and appeared to suppress H. zea populations. The predominate parasite species was Microplitis croceipes (Cresson) with some parasitism by Cotesia marginiventris (Cresson), Meterous autographae Meusebeck, and Winthemia rufopicta (Bigot). The date of the peak weekly capture of moths explained 99.7 of subsequent larval densities in soybeans, while the average weekly moth catches did not. The earlier moth peak in 1995 corresponded with higher populations of larvae, while the later peaks in 1996 and 1997 were followed by very low, sub-economic larval populations. Departures from normal for precipitation and temperature during August explained 99.8 and 95.3, respectively, of the variation in the date of peak moth capture.

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