Potential of Heterorhabditis bacteriophora JAAN-19 for sustainable management for prickly pear cactus weevil Metamasisus (Syn. Cactophagus) spinolae

Abstract

The prickly pear cactus, is a crop of cultural, gastronomic, and economic significance in Mexico due to its diverse uses. One of the major challenges to its yield is the cactus weevil. While agrochemicals have been the primary method of control, various alternatives have been explored for sustainable agriculture using traps, parasitoids and entomopathogenic fungi with differential mortality between male and female pests, with some reaching a maximum effectiveness of 70-80%. This study explored the potential of the nematode identified as Heterorabditis bacteriophora JAAN-19 as a biocontrol agent. In vitro, a concentration of 1000 Jl/weevil achieved 90% mortality in females and males after six days. Notably, the substrate experiments, mimicking real-world conditions, demonstrated the nematode's strong searching and infective capacity, reaching 97% mortality at the same concentration within 6-8 days. Experiments revealed that the nematode's effectiveness depended on dose and exposure time, not the weevils' sex. Based on the experiment observations, the lethal dose (LD50) for the weevils was 138 Jl/weevil, and the dose for 90% mortality (LD90) was 463 Jl/weevil, both within a 6-8 day period. These findings support the high agrobiotechnological potential of H. bacteriophora JAAN-19 as a sustainable control strategy against the cactus weevil Metamasius spinolae.