Susceptibility of Populations of Anticarsia gemmatalis (Lepidoptera: Noctuidae) from Brazil and the United States to a Nuclear Polyhedrosis Virus1

Abstract

Populations of velvetbean caterpillar, Anticarsia gemmatalis Hübner, were sampled in different regions of Brazil (Dourados, Londrina, Rancho Alegre, and Passo Fundo) and the United States (Texas and Louisiana). Laboratory colonies were established in each respective country, and larvae were bioassayed with a nuclear polyhedrosis virus (NPV), isolate LD-79, obtained in Londrina, PR, Brazil, in 1979. Log-dose-probit regression lines and associated parameters were used to compare susceptibility of the populations to the NPV. The Brazilian A. gemmatalis populations did not differ significantly from one another based on overlap of 95% confidence limits of median lethal concentrations (LC50). However, the LC50 was positively correlated with the number of years that field sites had been sprayed with NPV. Two A. gemmatalis populations from the United States did not differ significantly in their susceptibility to the virus.