Side effects of Bacillus thuringiensis on the parasitoid Palmistichus elaeisis (Hymenoptera: Eulophidae)

The endoparasitoid wasp Palmistichus elaeisis Delvare & LaSalle (Hymenoptera: Eulophidae) is used to control defoliating lepidopteran pests. Chemical insecticides are not compatible with natural enemies, but bioinsecticides, such as Bacillus thuringiensis Berliner (Bt), have great potential for use in integrated pest management. However, interactions between Bt and P. elaeisis still need to be investigated. This study aimed to evaluate the effects of Bt on parental and first-generation P. elaeisis parasitizing Bt-susceptible and -resistant Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae). An additional aim was to determine the toxicity of Bt to susceptible third-instar S. frugiperda larvae. Larvae were exposed to lethal concentrations (LC₅₀ and LC₉₀) of Bt and then allowed to be parasitized by P. elaeisis. Parasitoid longevity, immature production, reproductive performance, and behavioral responses were evaluated. Bt repelled P. elaeisis and reduced immature production. Parental and first filial generation parasitoids of both sexes emerged from Bt-treated larvae showed lower survivorship than controls. Parasitoids had poorer reproductive performance in Bt-susceptible and -resistant pupae than in untreated pupae. Palmistichus elaeisis emerged from Bt-susceptible and -resistant S. frugiperda showed altered host-searching behavior and reproductive parameters, which indicates low compatibility between the bioinsecticide agent and the parasitoid wasp.