Biocontrol potential of entomopathogenic fungi, nematodes and bacteria against Rhynchophorus ferrugineus (Olivier)

Abstract

Abstract Background The red palm weevil (RPW), Rhynchophorus ferrugineus (Olivier) (Coleoptera: Curculionidae), is a serious threat to date palms across the globe, causing heavy yield losses. The pest inflicts damage to palms stem and destroys vascular system; resultantly lower the vigor and affect the growth and yield. For ecological farming system, biological control of the pest is gaining increased interest due to hosts’ specificity, safety to human, animal and non-target organisms, and their compatibility to environment. Results In laboratory assay, Beauveria bassiana, Heterorhabditis bacteriophora and Bacillus thuringiensis var. kurstaki (Bt-k) alone and in combination against sixth instar larvae and adults of four distinct populations of RPW were applied. H. bacteriophora was more effective, followed by B. bassiana and Bt-k in alone treatments. While in combined treatments, the highest mortality was recorded for H. bacteriophora + B. bassiana combination (100% for both stages), followed by H. bacteriophora + Bt-k, (larvae 100%; adults 94.24%) and B. bassiana + Bt-k treatments (larvae: 87.01%; adults: 80.53%). Maximum rate of mycosis (larvae 85.74%; adults 69.07%), sporulation (larvae 189.22 conidia ml−1; adults 164.56 conidia ml−1), cadavers affected by nematodes (larvae 92.4%; adults 81.29%) and nematode production (larvae 178.78 IJs ml−1; adults 153.44 IJs ml−1) was observed where B. bassiana or H. bacteriophora was applied alone and the lowest (larvae 122.78 IJs ml−1; adults: 103.22 IJs ml−1) was recorded for H. bacteriophora + B. bassiana combination. Conclusions Entomopathogens can be effectively used alone and/or in integration to control RPW populations. Natural capability of entomopathogens to infect and disseminate into other hosts makes them excellent biocontrol agents to be incorporated in the IPM plan of RPW and to make palm growers confident with the use of the most promising microbial control agents.

Keywords

• Rhynchophorus ferrugineus
• Red palm weevil
• Beauveria bassiana
• Heterorhabditis bacteriophora
• Bacillus thuringiensis
• Entomopathogens