A new study published in Scientific Reports highlights a promising breakthrough in sustainable pest management for citrus orchards. Researchers evaluated three bacterial species—Streptomyces thinghirensis HM3, Streptomyces tricolor HM10, and Bacillus subtilis E5—against the citrus rust mite (Phyllocoptruta oleivora), a globally significant pest known for causing severe fruit damage and yield losses.
Under both laboratory and field conditions, S. thinghirensis HM3 emerged as the most potent agent, achieving up to 89.26% mite mortality in the lab and 84.47% in the field just four days after application. S. tricolor HM10 showed similarly high activity after six days, while B. subtilis E5 provided moderate control with mortality levels around 71–73% after one week.
Importantly, the study also assessed potential non-target effects on the beneficial predatory mite Amblyseius swirskii. All three bacterial species showed minimal impact on the predator, with corrected mortality remaining below 18% in laboratory trials and even lower under field conditions. This selectivity indicates strong compatibility with integrated pest management programs.
The researchers also reported that S. thinghirensis and S. tricolor significantly suppressed egg hatchability of P. oleivora, reducing hatching to 34–36%, compared to 96.87% in the untreated control. B. subtilis E5, however, did not affect egg hatching.
Genomic analysis further revealed a potential biosynthetic gene cluster in S. thinghirensis HM3 linked to actinomycin D production, alongside multiple proteases and protease inhibitors in both Streptomyces strains—compounds that may contribute to their acaricidal action.
The study concludes that these bacterial species—especially S. thinghirensis HM3 and S. tricolor HM10—represent effective, environmentally friendly alternatives to chemical acaricides. Their strong miticidal activity, limited non-target effects, and associated bioactive metabolites position them as promising candidates for future citrus orchard management strategies.
Reference
Al-Azzazy, M.M., Alhewairini, S.S. & Rehan, M. Biological control of citrus rust mite Phyllocoptruta oleivora by three bacterial species. Sci Rep 15, 37452 (2025). https://doi.org/10.1038/s41598-025-21182-4
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