Efficacy of optical brightener formulations of Spodoptera exigua multiple nucleopolyhedrovirus (SeMNPV) as a biological insecticide in greenhouses in southern Spain

Abstract

Abstract The efficacy of optical brightener formulations of a native Spanish isolate of Spodoptera exigua multiple nucleopolyhedrovirus (SeMNPV) was determined for control of S. exigua on greenhouse grown sweet pepper (Capsicum annuum) in Almeria, Spain. In laboratory bioassays involving diet surface contamination, the 50% lethal concentration in fourth instars was reduced 25-fold and 5731-fold, compared to SeMNPV occlusion bodies (OBs) alone, or in mixtures with 0.1% and 1% of the stilbene-derived optical brightener leucophor AP, respectively. The efficacy of spray applications of 1 × 1012 OBs/Ha SeMNPV alone, or in mixtures with 0.1% leucophor AP, was tested in a greenhouse planted with sweet pepper. The prevalence of virus infection in larvae collected at intervals post-application and reared on artificial diet in the laboratory was very high (62–97% mortality). Compared to the treatment involving SeMNPV OBs alone, OBs applied in mixtures with leucophor AP resulted in a significant increase in the prevalence of infection in larvae collected at 2 days post-application, but not in insects collected subsequently. In contrast, a chemical insecticide treatment, lufenuron, performed poorly (