Biological characterization of two Spodoptera frugiperda nucleopolyhedrovirus isolates from Mexico and evaluation of one isolate in a small-scale field trial

Abstract

This study describes the biological activity of two Spodoptera frugiperda multiple nucleocapsid nucleopolyhedrovirus (SfMNPV) isolates recovered from the soil of maize crops in the states of Yucatán and Chiapas, Mexico (Sf-YUC and Sf-CHI). The biological activity was determined for four Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae) field populations: Sf-Motozintla, Sf-Erongaricuaro, Sf-Abasolo, and Sf-Culiacancito. As a reference, a laboratory colony (Sf-Lab) was used. Biological characterization was compared with that for a characterized SfMNPV isolate from Nicaragua (Sf-NIC). The LC50 values for both the Sf-NIC and Sf-CHI isolates did not differ in any of the insect populations tested. In contrast, the Sf-YUC isolate was less active than the Sf-NIC isolate in the Sf-Motozintla population, but this isolate was more active in the Sf-Erongaricuaro and Sf-Abasolo populations. The killing speed and OB productivity were variable among isolates in each insect population. A small-scale field trial was performed to evaluate the degree of pest control achieved by the Sf-YUC isolate, applied at a rate of 3 × 1012 OBs/ha, in maize grown in central Mexico. The larval mortality caused by the virus was 58%, 78%, and 84% at 2, 5, and 7 d post application, respectively. At 7 d post application, the incidence of insect parasitoids in the virus treatment was significantly lower than in the control. In conclusion, the insecticidal characteristics of both Mexican isolates (Sf-CHI and Sf-YUC) varied according to their insect population. In addition, the Sf-YUC isolate may be suitable as the basis for a biopesticide for the control of S. frugiperda in Mexico.