The effect of Streptomyces fradiae strain JB-1 on Bactrocera dorsalis species complex pupal development in various soil levels

The Bactrocera dorsalis species complex comprises major pests of various tropical fruit and vegetable crops. Populations typically increase during the rainy season, a period when pesticide applications are often less effective. Additionally, pupation in the soil further complicates control efforts. Streptomyces spp., entomopathogenic bacteria, show potential as biological agents against the pupal stage of fruit flies. This study aimed to evaluate the effects of S. fradiae strain JB-1 on pupal mortality, adult development type, and developmental time in soils of varying depths. The mean percentages of pupal mortality, successful imago, and abnormal imago differed significantly among soil treatments, whereas the mean percentage of normal imago did not. Similarly, significant differences in the mean percentages of dead pupae, successful imago, and normal imago were observed across soil depths, but no significant differences were found for abnormal imago. Application of S. fradiae extended the pupal stage duration across all imago parameters, while soil depth had no significant effect. These findings suggest that S. fradiae strain JB-1 is effective in controlling fruit fly pupae in soils of varying depths. This study provides a foundation for integrating entomopathogenic Streptomyces spp. into fruit fly control strategies targeting the pupal stage.