Mortality and Production of Occlusion Bodies in<i>Spodoptera frugiperda</i>Larvae (Lepidoptera: Noctuidae) Treated with Nucleopolyhedrovirus

Abstract

The fall armyworm (FAW), Spodoptera frugiperda is the main corn pest in Latin America. As an alternative to chemical insecticide applications, one isolate of Spodoptera frugiperda nucleopolyhedrovirus from soil of an experimental field in Saltillo, Coahuila, Mexico was evaluated. Egg masses of the pest were superficially inoculated by the immersion method, with different nucleopolyhedrovirus concentrations expressed as occlusion bodies/mL (OBs/mL). Artificial diet was also inoculated with different viral concentrations and used to conduct bioassays on first to sixth instar larvae to determine the number of OBs produced per larva. Another assay was performed under greenhouse conditions to evaluate four baculovirus formulations. The use of the immersion method on egg masses caused the highest mortality rates recorded in the larval stage (74.37%), mainly in the first instar, with 64.05% mortality. The number of OBs produced per larva ranged from 5.15 × 106 to 2.3 × 109, where fifth and sixth instar larvae produced the highest amount. OBs produced by weight unit of larva were registered and higher values were found in the last larval instars. In the baculovirus formulations tested under greenhouse conditions, the mixture with maize flour and starch resulted in significantly increased mortality rates.