Influence of temperature on occlusion body production in a Mexican isolate of Spodoptera exigua multiple nucleopolyhedrovirus

In vivo production of baculoviruses requires optimisation studies for each host-virus system. Considering the potential of a Mexican isolate of Spodoptera exigua multiple nucleopolyhedrovirus (SeSIN6) for developing a biopesticide, here, a compartmentalised tray system and a cool-textured diet were used to determine the effect of incubation temperature on the pathogenicity, speed of kill, and production of occlusion bodies (OBs). All measurements were compared with a characterised American nucleopolyhedrovirus isolate (SeUS2). Incubation of fourth instar S. exigua at 20, 25, and 30°C did not significantly affect the mortality caused by either isolate, although a delay in virus infection was observed at 20°C. The OB production of both isolates in infected larvae was significantly lower at 20°C than at 25 and 30°C. At all temperatures, the OB production of the SeSIN6 isolate was higher than the SeUS2 isolate. The production of OBs per mg larva was significantly higher at 30°C for both isolates. A positive correlation was observed between larval weight gain and the production of OBs/larva at all temperatures, whereas a negative correlation was observed between larval gain weight and OBs/mg of larval weight in most of the treatments. We conclude that incubation temperatures of 25 and 30°C are optimal for OB production per larva in both isolates tested. Further studies are needed to examine other factors that can improve the production of Mexican SeMNPV isolates.