Biological control potential of Moroccan entomopathogenic nematodes for managing the flatheaded root-borer, Capnodis tenebrionis (Linné) (Coleoptera: Buprestidae)

Abstract

The flatheaded root-borer Capnodis tenebrionis (Linné) (Coleoptera: Buprestidae) causes serious damage to stone fruit trees in Mediterranean countries. The use of entomopathogenic nematodes (EPNs) is an eco-friendly tool that can efficiently control C. tenebrionis. In this study, the efficacy of five EPN isolates native to Morocco was assessed against different developmental stages of C. tenebrionis in laboratory and greenhouse experiments. In Bioassay 1, the susceptibility of neonate larvae of C. tenebrionis to EPNs was evaluated according to temperature (25 and 32 °C) and soil moisture (5 and 10%). The greatest mortality rates were observed for Heterorhabditis bacteriophora HB-MOR7 (97.5%) and Steinernema feltiae SF-MOR9 (95%) with the 10% soil moisture-25 °C combination. S. feltiae SF-MOR9 and Heterorhabditis sp. HJo-MOR14 induced moderate to high mortality regardless of the temperature-soil moisture combination. In Bioassay 2, Heterorhabditis sp. HJo-MOR14 performed better against adults of C. tenebrionis than the other isolates. In addition, no difference in susceptibility between females and males was recorded for each EPN isolate. In pot experiment, more live larvae of C. tenebrionis were found in roots and collar of almond trees for HJo-MOR14 (0.93) than HB-MOR7 (0.47) and SF-MOR9 (0.43). Furthermore, treatments by SF-MOR9 and HB-MOR7 ensured low infestations of trees by larvae of C. tenebrionis than the treatment by HJo-MOR14 (36.7, 43.3 and 66.7% respectively). Our results show that Moroccan EPN isolates have potential as alternative methods for the control of C. tenebrionis.