Biocontrol potential of Heterorhabditis bacteriophora (Poinar) multiplied in black soldier fly larvae against rhinoceros beetle Oryctes rhinoceros (L.)
Department of Entomology, College of Agriculture, Vellayani, Kerala Agricultural University, Kerala, India Corresponding e-mail: anjalypv123@gmail.com
DOI: https://doi.org/10.37855/jah.2026.v28i02.52
The coconut rhinoceros beetle (CRB), Oryctes rhinoceros (L.) (Coleoptera: Scarabaeidae), is a major pest of coconut, causing more than 10 % yield loss. Adult beetles bore into unopened leaves and inflorescences, while grubs develop in decomposing organic matter. In this study, the infectivity of the entomopathogenic nematode (EPN) Heterorhabditis bacteriophora, multiplied in black soldier fly larvae (BSFL), Hermetia illucens L., was evaluated against all three larval instars of CRB using different doses of infective juveniles (IJs). All instars showed dose dependent mortality, with no mortality at very low doses (100-300 IJs per insect). In the first and second instars, mortality began at 500 IJs per insect and increased steadily with dose and time, reaching 100 % at 20000 IJs by 6 DAT (days after treatment) and at 10000 IJs by 10 DAT. At lower doses (500-1000 IJs), the first instar reached only about 35 % mortality, whereas the second instar showed slightly higher susceptibility, recording 46.67 % mortality by 12 DAT. The third instar was less susceptible, with mortality beginning later and reaching only 40 % at 20000 IJs by 12 DAT. A t-test comparing nematodes produced from BSFL and greater wax moth larvae (Galleria mellonella) indicated no significant difference in infectivity. The results confirm that H. bacteriophora is highly effective against the second instar of CRB. Even though wax moth larvae are the universal host for the multiplication of EPN, BSFL offer a simpler and efficient alternative host for producing these nematodes, supporting their use as a valuable tool in integrated pest management.
