Biological activity of Bacillus spp. evaluated on eggs and larvae of red palm weevil Rhynchophorus ferrugineus

Abstract

This study was conducted to characterize the Bacillus populations associated with dead Rhynchophorus ferrugineus, to develop a biological control for the red palm weevil. Dead adult beetles, collected throughout Sicily, were used for isolating internal and external spore forming bacteria (SFB) microbiota. The isolates, preliminarily allotted to the Bacillaceae family, were tested at four concentrations (10 3 to 10 6 CFU/mL) for their ability to inhibit hatching of eggs of R. ferrugineus and were used at 10 6 CFU/mL to monitor their insecticidal activity against 10-day-old larvae. Total amounts of SFB measured outside the skeleton and in the inners part of the beetles were 5.59-6.94 and 5.17-7.05 Log CFU/g, respectively. Hatching was markedly inhibited by nine isolates, representing nine distinct strains of seven species (Bacillus amyloliquefaciens, Bacillus cereus, Bacillus licheniformis, Bacillus megaterium, Bacillus pumilus, Bacillus subtilis, and Lysinibacillus sphaericus), especially by the strains B. pumilus GC43 and GC51, which exhibited lethal concentrations 50 (LC50) values of 1.60×10 3 and 9.84×10 3 CFU/ mL, respectively. Among all the strains tested, only B. licheniformis CG62 exhibited significant insecticidal activity against red palm weevil larvae. The Bacillus isolates characterized and tested in this study inhibited the hatching of red palm weevils in a contact-dependent manner. Thus, these isolates can be used as a preventive rather than as a curative treatment.

Potential role of microbial pathogens in control of red palm weevil (Rhynchophorus ferrugineus) ‐ A Review

“…B. thuringiensis , B. sphaericus and B. megaterium were isolated from larvae of RPW, and in preliminary bioassays these strains revealed a weak pathogenic effect on eggs of RPW (Francesca et al ), which might be perhaps correlated with antimicrobial compounds on this stage (Mazza et al ). Recently, Francesca et al () isolated distinct strains of seven species from RPW beetle cadavers ( Bacillus cereus , Bacillus amyloliquefaciens , Bacillus subtilis, Bacillus megaterium , Bacillus licheniformis , Bacillus pumilus , and Lysinibacillus sphaericus ) from all over Sicily. In Taiwan fourteen bacterial strains were isolated from RPW.…”

“…Future experiments to control RPW by deploying microorganisms could look further into the molecular mechanism of disease resistance in RPWs especially the immune system. Most recently, Francesca et al () tested nine distinct stains of bacterium that significantly reduced egg hatching, while B. licheniform is caused significant mortality in RPW larvae.…”

Toxicity of Plant Secondary Metabolites Modulating Detoxification Genes Expression for Natural Red Palm Weevil Pesticide Development

“…Different environmental friendly strategies including entomopathogenic fungi [ 4 , 5 , 6 ], nematodes [ 7 ], bacteria [ 8 , 9 ], development of pheromone traps [ 10 , 11 , 12 , 13 ], sterile insect technique [ 14 , 15 , 16 , 17 ], and plant based insecticides [ 18 , 19 , 20 , 21 ] remained the subject of previous research investigations. Among them, plant-based products especially plant secondary metabolites are the most promising alternatives to environmental deteriorating insecticides.…”

Susceptibility and Immune Defence Mechanisms of Rhynchophorus ferrugineus (Olivier) (Coleoptera: Curculionidae) against Entomopathogenic Fungal Infections

“…These setbacks have led to the search for alternative methods of RPW control, particularly bio-control agents. Previous studies have reported the use of bacteria [ 3 ], fungi [ 4 , 5 , 6 ], nematodes [ 7 ], and parasitoids [ 8 ] against RPW. However, the use of entomopathogenic fungi, is a promising alternative for reversing the hazardous dependence of agriculture on synthetic insecticides.…”