Yu-Chen Pu1,2, Tian-Ling Ma1,2, You-Ming Hou1,2, Ming Sun3. 1. State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, Fujian Agriculture and Forestry University, Fuzhou, Fujian, China. 2. Fujian Province Key Laboratory of Insect Ecology, Department of Plant Protection, Fujian Agriculture and Forestry University, Fuzhou, Fujian, China. 3. Department of Life Science, Huazhong Agricultural University, Wuhan, Hubei, China.
Abstract
BACKGROUND: The red palm weevil (RPW), Rhynchophorus ferrugineus, 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 LC50 was 4.92 × 109 CFU mL-1 15 d after feeding; the LT50 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.
BACKGROUND: The red palm weevil (RPW), Rhynchophorus ferrugineus, 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 LC50 was 4.92 × 109 CFU mL-1 15 d after feeding; the LT50 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.