Effects of heat-sensitive agents, soil type, moisture, and leaf surface onpersistence of Anticarsia gemmatalis (Lepidoptera : Noctuidae) nucleopolyhedrovirus

In a laboratory experiment, persistence of Anticarsia gemmatalis Hubner nuc leopolyhedrovirus (AgNPV) was significantly lower in marsh soil than in agr icultural soil. AgNPV was inactivated significantly more quickly in soil a t- 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 t han in autoclaved soil. AgNPV stored in unautoclaved marsh water lost 99% o f 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 exam ined on foliage of soybean, Glycine mar (L.) Merrill, versus deer pea, Vign a luteola (Jacq.) Benth, a wild host plant of A. gemmatalis. AgNPV sprayed on upper leaf surfaces lost greater than or equal to 60% of its activity wi thin 2 d, whereas the virus sprayed on the underside of foliage lost less t han or equal to 13% in the same time period, regardless of host plant. The results of the soil and water persistence experiments indicate that classic al biological control of A. gemmatalis with AgNPV is less likely to succeed in wild, coastal legumes than in the soybean agroecosystem.