Moroccan entomopathogenic nematodes for sustainable control of Dactylopius opuntiae

Abstract

Dactylopius opuntiae (carmine cochineal) is an invasive insect that damages cactus pear crops in Morocco. This study evaluated the laboratory pathogenicity of Moroccan strains of two entomopathogenic nematodes (Steinernema feltiae SF-MA1 and Heterorhabditis bacteriophora HB-MA2) against adult females of D. opuntiae. The experiments included five concentrations of infective juveniles (100, 200, 400, 600, and 800 juveniles per milliliter) and three temperatures (20, 25, and 30 °C). Mortality was assessed from 24 to 120 h and corrected using Abbott’s formula. The data were analyzed using two-way analysis of variance, probit regression, and response surface analysis. Mortality varied with nematode species, concentration, exposure time, and temperature. Overall, mortality increased with concentration and exposure time, and the dose–temperature interaction additionally determined nematode efficacy. H. bacteriophora achieved its highest mortality and lowest median lethal concentration at 25 °C, whereas S. feltiae was most effective at 20 °C. Response surface analysis identified combinations of moderate temperatures and high doses that maximized mortality. These findings indicated that locally adapted entomopathogenic nematodes may be promising candidates for D. opuntiae control. However, semi-field and field experiments are required to validate their use in cactus pear orchards.