Comparative Damage and Leaf Area Consumption By the Tobacco Budworm and Corn Earworm on Maryland Tobacco12

Abstract

Field and field cage studies were conducted in 1978 to compare larval injury of the tobacco budworm, Heliothis virescens (F.), and corn earworm, H. zea (Boddie), to Maryland variety 609 tobacco plants. Results of the field study showed that for both species, nearly 100% of all damage (defoliation and topping damage) was attributed to the 4th and 5th instars. Of the total number of leaves lost via defoliation, 66.56 and 91.88% were caused by 5th-instar budworm and earworm, respectively. Loss assessment was measured two ways, i.e., actual leaf loss (LLa) (area of damaged leaf vs. predicted whole leaf area) and observed defoliation (Dab) (leaf loss vs. remaining leaf area), and measurements indicated that plants compensated for leaf loss by increasing the laminal area of damaged leaves. Results from the field cage study showed that no significant differences existed between species for many damage parameters. However, the budworm significantly damaged more leaves ( P < 0.029), consumed more foliage ( P < 0.05), and was responsible for a greater loss in leaf guality than the earworm. The results suggest that in formulating management decisions, population estimates should be confined to the last two instars of both species.