Abstract
Entomopathogenic nematodes (EPNs) are a group of biological control agents that are characterized by their ability to search for hosts, safety to non-target insects and environment, and their ability to be used combined with agricultural chemicals. The objectives of this study were to isolate EPNs from agricultural soil in Egypt and study their virulence against the great wax moth, Galleria mellonella L. (Lepidoptera: Pyralidae), for further use in biological control program. Two out of 20 soil samples collected from orchards cultivated with olives and mango were positive for the presence of EPNs, using the Galleria baiting technique. The positive soil samples were sandy clay loam. Sequencing of the internal transcribed spacer (ITS) region indicated that the isolates obtained belong to Heterorhabditis indica. The ITS sequences were submitted to the National Center for Biotechnology Information (NCBI) and registered under the accession nos. MH553167 and MK300683. The efficacy of the isolates was tested on G. mellonella, using different nematodes’ concentrations. Using 50 IJs/larvae from H. indica Aborawash and ERSAG2 showed 100 and 86% mortality rate after 48 h, respectively. The penetration rate reported in dead G. mellonella was 40% at H. indica Aborawash, while it was 35% in case of ERSAG2.
Highlights
Entomopathogenic nematodes (EPNs) of the families Heterorhabditidae and Steinernematidae are obligate deadly insect parasites that spend part of their life cycles in hosts (Adams et al 2006)
The 2 positive soil samples were classified as sandy clay loam and the temperatures at all the 4 collecting points were reported as 25 °C
This agrees with the data presented by Singh et al (2015) and Laznik and Trdan (2016) who concluded that the application of Steinernema feltiae, S. carpocapsae, and H. bacteriophora at 20 and 25 °C resulted to mortality rates of over 57% for granary weevils
Summary
Entomopathogenic nematodes (EPNs) of the families Heterorhabditidae and Steinernematidae are obligate deadly insect parasites that spend part of their life cycles in hosts (Adams et al 2006). The life cycle of EPNs includes an egg stage, 4 juvenile stages, and an adult stage. The 3rd juvenile stage of EPNs is referred to be the “infective juveniles” (IJs) (Poinar 1990). Once the IJs penetrate the host, they release bacteria that live symbiotically within the EPNs’ gut. Due to the extensive use of insecticides, insects have acquired resistance during recent decades (Andaló et al 2018). EPNs represent an alternative control method to insecticides as it is an environmentally safer option, not harmful to humans, animals, plants, or earthworms (Le Vieux and Malan 2013)
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