Acaricidal effects of two native isolates of entomo-pathogenic bacteria Photorhabdus luminescens (Thomas & Poinar) against spider mite, Tetranychus truncatus Ehara (Acari: Tetranychidae)

Two local isolates of P. luminescens (NCBI GenBank Accession numbers ON627692, and ON627695) were evaluated for their bio-efficacy against the spider mite Tetranychus truncatus in the laboratory. Different concentrations (10(4) to 10(8) CS/CFS mL(-1)) of cell suspension (CS) and cell-free supernatant (CFS) of the bacterial isolates obtained by centrifugation (4000 rpm for 20 min) were topically applied on eggs and adults of spider mites. The observations on ovicidal as well as adulticidal activity of bacterial isolates were recorded at 24, 48, and 72 h intervals. The bacterial isolates showed significant ovicidal and adulticidal properties for both CS and CFS after 72 h of treatment application. The isolate CNT1 recorded 84.00 and 58.67% mortality of eggs and 100 and 97.33% mortality of adults, respectively, for CS and CFS, at 10(8) mL(-1) concentration. At the same concentration, the isolate ODA showed 44.00 and 84.00% mortality of eggs and 98.67 and 100% mortality of adults, respectively, for CS and CFS. The study identified two bacterial isolates of P. luminescens with appreciable acaricidal properties that can be exploited as a potential biocontrol agent against spider mite pests of crops.