Insecticidal activity of a Moroccan strain ofStreptomyces phaeochromogenesLD-37 on larvae, pupae and adults of the Mediterranean fruit fly,Ceratitis capitata(Diptera: Tephritidae)

Abstract

AbstractThe Mediterranean fruit fly (medfly),Ceratitis capitata, is considered the most important fruit pest worldwide. Its management is mainly based on the use of chemical insecticides. Although these conventional pesticides are effective at high doses, they cause considerable human health and environment problems. Thus, the aim of this study was to assess insecticidal activity of Moroccan actinobacteria againstC. capitata. A total of 12 preselected actinobacteria isolated from various Moroccan habitats were screened for their insecticidal activity against larvae, pupae and adults ofC. capitata. Four actinobacteria isolates were significantly active against the first-instar larvae, and nine were active against the medfly adult, while no significant mortality was obtained against the third-instar larval and pupal stages. Among the selected isolates, the biological screening revealed that strainStreptomycesLD-37, which showed 99.4% similarity withStreptomyces phaeochromogenes, exhibited the maximal corrected larval mortality of 98%. Moreover, the isolates AS1 and LD-37 showed the maximum significant corrected mortality against adults of 32.5 and 28.2%, respectively. The crude extract obtained from a fermented culture of strainS. phaeochromogenesLD-37 was separated into six fractions by thin layer chromatography. Fractions F3 and F4 caused a significant corrected larval mortality of 66.7 and 53.3%, respectively; whereas the maximum reduction in adult emergence was obtained with fraction F4. This finding could be useful for utilizingS. phaeochromogenesLD-37 as an alternative to chemical insecticides in pest management ofC. capitata.