Norman Marston

Natural and induced epizootics of Nomuraea rileyi in soybean caterpillars

Abstract A heavy application of Nomuraea rileyi conidia significantly altered the epizootic pattern normally associated with soybean caterpillars. The initial detection and peak incidence of infected caterpillars from treated plots was advanced at least 14 days compared with untreated plots. The peak therefore occurred prior to and during the stages of soybean growth that were most sensitive to defoliation by caterpillars (R-8, R-9). In untreated plots the peak incidence of infection occurred after the damage had been done. Low populations of susceptible caterpillars (less than 1/row-ft) that are infected with N. rileyi may produce sufficient conidia to regulate incipient pest populations. The half-life of conidia applied to soybean foliage was 2 days, and only 3% of the original conidia activity was present after 9 days.