Laboratory Evaluation of Indigenous and Commercial Entomopathogenic Nematodes against Red Palm Weevil, Rhynchophorus ferrugineus (Coleoptera: Curculionidae).

Simple Summary: The red palm weevil, Rhynchophorus ferrugineus, is a major problem for palm plantations worldwide. While chemical pesticides are known to be effective, their environmental impact and insecticide resistance pose serious concerns. Biological control approaches, such as employing entomopathogenic nematodes, can mitigate these challenges by focusing on pests while avoiding harm to the environment or non-target organisms. Our findings show that indigenous and commercial EPNs have the ability to manage red palm weevils. As a result, alternate methods, such as the use of entomopathogenic nematodes, are critical for the sustainable control of red palm weevils. The red palm weevil (RPW) is a significant threat to date palms. Conventional pest control has been ineffective. This study aims to evaluate entomopathogenic nematodes (EPNs) indigenous to Saudi Arabia and commercial against RPW. We used 33 soil samples collected from four areas of Saudi Arabia. The indigenous EPNs were isolated and cultured using an insect baiting method to obtain infective juveniles. Pathogenicity bioassays were conducted against different stages of RPW, including eggs, larvae, and adults. The bioassay was performed using all the isolates at 1 × 106 IJ/mL. Distilled water was used as a control. The results revealed that only 9.09% of soil samples contained positive EPNs. Through DNA sequencing analysis, the positive samples were identified as indigenous isolates belonging to Heterorhabditis indica and Steinernema carpocapsae EPN species. In pathogenicity tests, 90% mortality of RPW eggs was observed after five days. Similar mortality trends were seen in RPW larvae and adults, with 90% mortality recorded after ten days for all the EPN treatments. Mortality increased with the duration of post-EPN inoculation exposure. The 1 × 106 IJ/mL concentrations of EPN effectively killed various stages of RPW in the laboratory. More research is needed to test EPNs against RPW in the field. [ABSTRACT FROM AUTHOR]