Application of a Baculovirus of Pseudoplusia includens to Soybean: Efficacy and Seasonal Persistence 1

Abstract

A baculovirus of the soybean looper, Pseudoplusia includens (Walker), was applied at a rate of 247 LE/ha to soybean. Larval population levels, virus induced larval mortality and viral concentration in the soil and on the foliage were monitored from August 1975 until August 1977. Viral applications resulted in epizootics in soybean looper populations reducing larval numbers. A significant reduction in larval numbers did not occur until 12 to 13 days after treatment. The virus persisted at high concentrations in soil from 2 weeks posttreatment through the fall. Viral concentration in the soil was reduced by November 1975. In 1976–1977, viral concentration in soil remained high (1.13 × 1014 PIB/ha) through May, after which it declined. Viral concentration in soil was not sufficient to initiate an epizootic in P. includens the following summer. By 72 h after treatment, viral concentration on foliage was low when compared with concentration immediately after virus application. After a substantial proportion of larvae had died, 6 to 7 days after treatment, high viral concentrations were detected on the foliage.