Mortality of the Corn Earworm (Lepidoptera: Noctuidae) on Sorghum Panicles in Georgia

Abstract

The mortality of the corn earworm, Helicoverpa zea (Boddie), on sorghum panicles in Georgia was determined in a 2-yr study. Percent total real mortality (rx) of H. zea exceeded 99% for each year and planting date. Percent total real mortality was highest for eggs followed by 1st instars. Parasitization and predation were the primary mortality factors for eggs on sorghum panicles. Larval mortality was due in part to predation, parasitization, and infection by pathogens. Trichogramma pretiosum Riley was the only egg parasitoid observed on sorghum panicles. Orius insidiosus (Say) was the predominant predator of H. zea. Other predators observed feeding on H. zea included the big-eyed bug, Geocoris punctipes (Say), the spined soldier bug, Podisus maculiventris (Say), green lynx spiders, Peucetia viridans (Hentz), and lady beetles (mainly Hippodamia convergens Guérin-Méneville). A variety of parasitoids attacked larvae on sorghum. The braconid Cotesia marginiventris (Cresson) parasitized small to medium-sized larvae. The tachinids Eucelatoria rubentis Coquillett and Archytas marmoratus (Townsend) parasitized large larvae. Two pathogens, HzNPV, a naturally-occurring nuclear polyhedrosis virus of H. zea, and the fungus, Entomophthora aulicae (Reichardt) G. Winter, caused mortality of larvae. In conclusion, biological control by natural enemies of H. zea on sorghum panicles resulted in significant mortality for this pest.