Can rational sampling maximise isolation and fix distribution measure of entomopathogenic nematodes?

Abstract

Summary Entomopathogenic nematodes (EPN) can infect and kill a wide range of insect pests and are used as safe alternatives to chemical insecticides. Hence, a hypothesis was tested for obtaining EPN with high recovery frequency value and accurate distribution pattern based on combining four factors: favourable sampling method, time and site targeting and use of multiple extraction technique. As the extreme diversity of EPN sampling makes any generalisation from a given case study difficult, this functional sampling was limited to recovering EPN from citrus trees only in Egypt. It could both detect more EPN isolates and allow the application of different indices of dispersion to study their spatial distribution pattern. Therefore, stratified random and systematic sampling from weed-infested soil under tree canopy during the season of abundant insect pests was done, followed by multiple cycles of Galleria-baiting technique. Consequently, the nematodes were recovered from the seven surveyed groves (100%) and from 37 of 60 (61.7%) soil samples. The spatial distribution of these EPN isolates, previously identified as Heterorhabditis indica, was characterised using five dispersion indices, which were mainly a random rather than an over-dispersed distribution.