Components of seasonal soybean infestation by Heliothis zea in eastern Virginia, with emphasis on multivariate analysis of field susceptibility

Heliothis zea (Boddie) (Lepidoptera: Noctuidae) density, development, and relationships with host crops were studied in eastern Virginia. Six instars occur. The larval population in corn is the reservoir for the generation in soybeans. An estimator, based on the reservoir population, permitted calculation of the larval density in soybeans. An index, based on blacklight trap and emergence data, permitted precise timing ot peak moth flight to soybeans.

Regression analyses of biotic and abiotic factors revealed that soybean plant morphometrics best explained corn earworm densities.

Discriminant analyses on empiricala priori soybean field susceptibility categories (described by plant morphometrics) classified five levels of anticipated maximum larval densities 80 - 98 percent correctly. Development of highest larval densities was synchronized with overall plant growth and specific pod development: third and fourth instars were present during rapid pod elongation, while fifth and sixth were present during rapid pod volume increase.