Professor & Extension Specialist North Carolina State University Plymouth, North Carolina
Helicoverpa zea (Boddie), also known as bollworm, corn earworm and tomato fruitworm, is a polyphagous pest that has causes serious damage on crops such as soybeans Glycine max (L.). In both determinate and indeterminate soybeans, H. zea larvae are most commonly found on leaves, compared to blooms, stems, and pods and are distributed evenly throughout the plant canopy. In contrast, H. zea adults prefer to oviposit near the upper part of the plant canopy in soybeans with a determinate growth habit. Ovipositional preferences are unknown for soybeans with an indeterminate growth habit. We hypothesized that H. zea vertical distribution might differ between soybean growth habits because reproductive tissue availability varies between growth habits. Field and greenhouse experiments were planted with varieties sharing the same maturity group (two MG5.2 varieties and two MG 5.9 varieties), but having different growth habits. Field experiments relied on natural infestations, while greenhouse experiments relied on artificial infestations. We counted the number of H. zea eggs and neonates on each plant tissue type was recorded from each of three equal parts in the plant canopy: upper, middle and lower. Eggs and neonates were most common at the top of the plant and on leaves in both types of growth habits in both the field and greenhouse experiments. These results improve our understanding of H. zea ecology in soybeans and demonstrate that ovipositional choice is likely independent of reproductive tissue availability between growth habits. Finally, this information may help improve recommendations for managing H. zea in soybean.