Combination of a Baculovirus with biorational compounds for the control of the fall armyworm.

Abstract

The toxicity of azadirachtin and methoxyphenozide, alone and in interaction with the Spodoptera frugiperda Nucleopolyhedrovirus (SfMNPV) was evaluated with a future vision for the control of this lepidopteran called the fall armyworm. Ingestion bioassays were carried out where the third-stage larvae were fed with diet mixed with a range of seven (0.316 to 316 mg a.i./kg of diet) and five concentrations (0.0316 to 3.16 mg a.i. / kg) of azadirachtin and methoxyphenozide, respectively. For the combinations of the virus with the compounds, three concentrations of the pathogen were used: 5.4 × 102, 4.62 × 104, and 8.81 × 105 occlusion bodies (o.c./ml), which were inoculated through the drop ingestion method. Inoculation was carried out before exposure to the diet contaminated with the insecticides. S. frugiperda was susceptible to all the compounds, although to a greater degree to methoxyphenozide (9.3-fold) compared to azadirachtin. The combination of the highest concentration of SfMNPV with two concentrations of azadirachtin caused an increase in larval mortality. The bioassay of  fMNPV - methoxyphenozide decrease in mortality compared to virus alone in the two lowest concentrations of this insecticide. Combination trials of AZA and MET with SfMNPV could be considered as SfMNPV enhancing agents.