Efficiency of Bacillus thuringiensis and Bacillus cereus against Rhynchophorus ferrugineus

SIMPLE SUMMARY: Rynchophorus ferrugineus Olivier, the red palm weevil (RPW), is a damaging insect that often severely infests palm trees. Since insecticides have a detrimental environmental impact and may lead to pesticide resistance, new biological control methods are needed. Bacteria from many different species affect the RPW larval growth, health, and immunity. The work evaluates the crosstalk between the RPW and rhizosphere bacteria. Four bacterial isolates, three belonging to Bacillus cereus and one belonging to B. thuringiensis, had a significantly higher impact on the mortality of the larvae and adults of the RPW than other bacteria that were tested did. The results emphasize the significant potential of developing new microbial resource-based management techniques for this pest. ABSTRACT: The Red Palm Weevil (Rhynchophorus ferrugineus (Oliv.) (Coleoptera, Dryophthoridae) is a well-known palm tree pest that has caused enormous economic damage all over the globe. Insecticides are still the primary method of controlling this pest at this period. However, field populations of RPW have been shown to be resistant to pesticides. Using Bacillus spp. might be one of the options for controlling R. ferruginous. In this study, 23 species of Bacillus spp. were isolated from the rhizosphere of date palm trees in Al Ahsa Oasis, Saudi Arabia. The isolates were identified using 16S rRNA gene sequencing. R. ferrugineus larvae and adults were tested on sugarcane pieces that were treated with the B. thuringiensis strain PDC-AHSAA1 and B. cereus strains (PDC-AHSAA2, PDC-AHSA3 and PDC-AHSA4). The LC(50) values for larvae and adults were quite low when they were compared with those of the other isolated strains. The B. thuringiensis strain PDC-AHSAA1 was more effective against both the larvae and adults. The determined LC(50) values for B. thuringiensis ranged from 4.19 × 10(7)–3.78 × 10(9). After 21 days, the data on larval mortality and body weight were evaluated. The surviving larvae that were treated with the bacterial isolates did not acquire a substantial weight. For the RPW larvae and adults, the mortality and corrected mortality death rates were increased by increasing the concentration of B. thuringiensis. In conclusion, Bacillus-treated diets negatively influenced the growth and development of the RPW. This research reported on the interaction between the RPW and the rhizosphere Bacillus spp. and highlighted the tremendous potential for the development of microbial resource-based control strategies for this pest.