Effects of Heat-Sensitive Agents, Soil Type, Moisture, and Leaf Surface on Persistence ofAnticarsia gemmatalis(Lepidoptera: Noctuidae) Nucleopolyhedrovirus

Abstract

In a laboratory experiment, persistence of Anticarsia gemmatalis Hubner nucleopolyhedrovirus (AgNPV) was significantly lower in marsh soil than in agricultural soil. AgNPV was inactivated significantly more quickly in soil at −0.3 bar water potential than in soil at water potentials of 0 bar or −5 bar. Loss of AgNPV activity was significantly faster in unautoclaved soil than in autoclaved soil. AgNPV stored in unautoclaved marsh water lost 99% of its activity within 64 d, whereas AgNPV in distilled water or autoclaved marsh water remained 98–99% active after the same time period. The soil and marsh-water results indicate that 1 or more heat-sensitive agents, perhaps microorganisms, were inactivating AgNPV. The persistence of AgNPV was examined on foliage of soybean, Glycine max (L.) Merrill, versus deer pea, Vigna luteola (Jacq.) Benth, a wild host plant of A. gemmatalis. AgNPV sprayed on upper leaf surfaces lost ≥60% of its activity within 2 d, whereas the virus sprayed on the underside of foliage lost ≤13% in the same time period, regardless of host plant. The results of the soil and water persistence experiments indicate that classical biological control of A. gemmatalis with AgNPV is less likely to succeed in wild, coastal legumes than in the soybean agroecosystem.