Efficiency of Bacillus thuringiensis and Bacillus cereus against Rhynchophorus ferrugineus

Abstract

The Red Palm Weevil (<i>Rhynchophorus ferrugineus</i> (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 <i>Bacillus</i> spp. might be one of the options for controlling <i>R. ferruginous</i>. In this study, 23 species of <i>Bacillus</i> 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. <i>R. ferrugineus</i> larvae and adults were tested on sugarcane pieces that were treated with the <i>B. thuringiensis</i> strain PDC-AHSAA1 and <i>B. cereus</i> strains (PDC-AHSAA2, PDC-AHSA3 and PDC-AHSA4). The LC₅₀ values for larvae and adults were quite low when they were compared with those of the other isolated strains. The <i>B. thuringiensis</i> strain PDC-AHSAA1 was more effective against both the larvae and adults. The determined LC₅₀ values for <i>B. thuringiensis</i> ranged from 4.19 × 10⁷-3.78 × 10⁹. 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 <i>B. thuringiensis</i>. In conclusion, <i>Bacillus</i>-treated diets negatively influenced the growth and development of the RPW. This research reported on the interaction between the RPW and the rhizosphere <i>Bacillus</i> spp. and highlighted the tremendous potential for the development of microbial resource-based control strategies for this pest.