Efficacy of Bacillus thuringiensis and Beauveria bassiana Against Red Palm Weevil Rhynchophorus ferrugineus Olivier (Coleoptera: Curculionidae)

The use of bio-pesticides is the potential alternate of synthetic residual insecticides to cope with the problem of resistance among different insect pests while posing no threats to the environment and biological control agents. Laboratory trials were conducted in the Microbial Control Laboratory, Department of Entomology, University of Agriculture, Faisalabad (UAF), Pakistan, during 2017–18 to investigate the effect of Beauveria bassiana (Balsamo) Vuillemin (1.8 × 107 and 1.8 × 108 conidia/ml) and Bacillus thuringiensis (Berliner) at a dose rate of (0.5 and 1 µg/g) alone and in combination against fifth and sixth larval instars of Rhynchophorus ferrugineus Olivier (Curculionidae: Coleoptera). The insects were exposed to fungal and bacterial treatments by larval immersion and diet incorporation method, respectively. Results revealed that the combined application of B. bassiana at the rate of 1.8 × 108 conidia/ml and B. thuringiensis at 0.5 and 1 µg/g exhibited synergistic effects, while combination of lower fungal concentration with both dose rates of B. thuringiensis showed additive effect against target instars of R. ferrugineus. Moreover, the mortality data showed that fifth instar larvae were more susceptible to microbial treatments than sixth instar. Maximum mycosis and sporulation was recorded in the cadavers of R. ferrugineus where B. bassiana was applied individually at dose rate of 1.8 × 107 conidia/ml. The present work suggests that B. bassiana in combination with B. thuringiensis could be a cost–benefit strategy against R. ferrugineus on date palms.