An entomopathogenic bacterium strain, Bacillus thuringiensis , as a biological control agent against the red palm weevil, Rhynchophorus ferrugineus (Coleoptera: Curculionidae)

BACKGROUND The red palm weevil ( RPW ), Rhynchophorus ferrug ineus, is an invasive wood‐boring insect that damages palms and sugarcane. Bacillus thuringiensis ( Bt ) is an entomopathogenic bacterium which has been modified into various strains and widely used in pest management. The aim of this study was to evaluate the susceptibility of RPW to the HA strain of Bt . RESULTS Five concentrations of Bt bioassays were used on RPW eggs, second instars and fourth instars. Average egg hatching rates exceeded 85% using Bt suspensions or distilled water. Hatch times were extended significantly using higher Bt concentrations. For second instar larvae, the LC 50 was 4.92 × 10 9 CFU mL −1 15 d after feeding; the LT 50 values decreased with each higher concentration. The corrected mortality of second instars increased significantly with increased concentrations after 15 d, ranging from 16.97% to 94.32%. Significant differences occurred in the boring activity of fourth instars when dipped in Bt suspensions or crawling on treated sugarcane. Bacterial infection in dead larvae was confirmed using molecular techniques. CONCLUSION Our results indicated that Bt can be used in RPW control as a potential biological control agent and can effectively reduce palm trees damage.