Pathogenicity and compatibility studies of native Tolypocladium inflatum and Clonostachys krabiensis against Tetranychus urticae

The twospotted spider mite (TSSM), Tetranychus urticae Koch (Acari: Tetranychidae) is a major pest of field and greenhouse crops leading to qualitative and quantitative losses. Various chemical-based acaricides are being used for its management that pose risks to human health, environment and non-targeted organisms besides the development of resistance and resurgence of the pests. Therefore, alternative mite management practices are being promoted and implemented. Amongst them, entomopathogenic fungi (EPF) like Beauveria bassiana and Metarhizium spp. are being used globally, although new alternative EPF are required. Keeping this in mind, the present study was comprehended to determine the pathogenicity of native EPF, viz., Tolypocladium inflatum (Hypocreales: Ophiocordycipitaceae) and Clonostachys krabiensis (Hypocreales: Bionectriaceae) against different life stages of TSSM under laboratory conditions. The results indicated that adults are more vulnerable to studied fungi followed by nymphs and eggs of TSSM. The combined application of T. inflatum and C. krabiensis was significantly effective in controlling TSSM adults (99.33%) followed by T. inflatum (93.34%) and C. krabiensis (85.33%). According to the probit analysis, the combined application of studied EPF was found to be more effective against TSSM adults (LC50 = 6.72 x 10(4) conidia/mL) followed by T. inflatum (LC50 = 1.92 x 10(6) conidia/mL) and C. krabiensis (LC50 = 7.90 x 10(6) conidia/mL). All three treatments at higher concentrations significantly reduced the adult and nymph populations. Morphological investigations using scanning electron microscopy revealed the successful conidial adhesion, germination and penetration of native T. inflatum and C. krabiensis conidia on TSSM adults. Thus, the acaricidal potential of isolated native fungi can further be explored for developing fungal-based formulations for the sustainable management of mites.