Comparative susceptibility of Macrotermes bellicosus and Trinervitermes occidentalis (Isoptera: Termitidae) to entomopathogenic nematodes from Benin

Abstract

The differential susceptibility of two termite species, Macrotermes bellicosus and Trinervitermes occidentalis, to four entomopathogenic nematodes (EPN) isolates from Benin, Heterorhabditis indica Ayogbel, H. sonorensis Azohoue2, H. sonorensis Ze3 and Steinemema sp. Bembereke, was bio-assayed in laboratory tests. Soldiers of both M. bellicosus and T. occidentalis were similarly susceptible, but more susceptible than workers. Forty-eight h post-exposure of workers of M. bellicosus to 50 infective juveniles (IJ) of H. indica Ayogbel, H. sonorensis Azohoue2, H. sonorensis Ze3 and Steinemema sp. Bembereke for each termite resulted in 96.3, 87.9, 94.5 and 75.0% mortality, respectively, whereas under the same conditions, these EPN isolates caused 91.7, 98.5, 75.0 and 95.0% mortality of workers of T. occidentalis. Soldiers of M. bellicosus were the most invaded with 13.2-18.6% of applied IJ. Based on concentration-mortality data, the isolates H. indica Ayogbel and H. sonorensis Ze3 were more virulent to M. bellicosus with LC50values of 11 IJ, whereas Steinemema sp. Bembereke was the most virulent to T. occidentalis with LC50 values of 12 IJ. However, none of these isolates showed the highest penetration rate. All tested EPN isolates can recycle in both M. bellicosus and T. occidentalis. Our EPN repellent-dispersing assay did not show evidence that M. bellicosus and T. occidentalis would be able to detect the presence of IJ of any EPN isolates/species. However, it was observed that nematode dispersal occurred by infected termites or phoresis.

Searching for Better Methodologies for Successful Control of Termites Using Entomopathogenic Nematodes

“…[48,105] reported that the prevalence of infective juveniles (IJs) of EPNs in different habitats is affected by both intrinsic (behavioral, physiological, and genetic characteristics) and extrinsic (antibiotics, competition, natural enemies, temperature, soil moisture, pH, soil type, soil texture, relative humidity, UV radiation, and desiccation) factors. For experimental purposes, performance of EPNs is known by studying their ability to withstand conditions of drought, lack of oxygen, tolerance to heat [38,106], capacity to search for targeted pests in the soil at specific concentration [107], to kill them, and to multiply inside them. The nematodes' tolerance to biotic factors is also studied under laboratory conditions.…”

“…Most of the experiments designed in this regard are conducted using the larvae of the greater wax moth Galleria mellonella Linnaeus (Lepidoptera: Pyralidae), a model insect for EPN biology and pathogenicity studies [108]. Nematode isolates that perform best under laboratory conditions are then taken to semi-controlled and fields conditions [31,36,45] and tested against insect pests in biological control programs [31,36,106,109,110]. Grewal et al [111] observed greatest performance of indigenous EPN isolates as compared to exotic ones for the control of insect pests for being used in their natural environment.…”

“…Studies on the symbiotic bacteria of EPNs include evaluation of growth and virulence of the bacteria under heat and cold temperatures [124]. All these different experiments are not only conducted mainly under laboratory [38,106,109,118,119] but also under greenhouse and field conditions [129,130] either in open environments or in the dark [124].…”

Behaviour and Population Dynamics of Entomopathogenic Nematodes Following Application

“…Phoresis or other external contamination of animals is the most widely considered explanation for rapid short-range dispersal (Jabbour & Barbercheck, 2008) or long-range dispersal over several hundred meters or kilometres (Barratt, Blossey, & Hokkanen, 2006). Several types of soil invertebrates have potential to act as phoretic hosts for EPN, including earthworms (Campos-Herrera, Trigo, & Gutierrez, 2006;Shapiro, Tylka, Berry, & Lewis, 1995), isopods (Eng, Preisser, & Strong, 2005), predatory carabid beetles (Mertz, Agudelo, Sales, Rohde, & Moino, 2014) and termites (Zadji, Baimey, Afouda, Moens, & Decraemer, 2014). However, only insects capable of flight will result in significant displacement of EPN from the site of application.…”

Nematode Pathogenesis of Insects and Other Pests

“…Phoresis or other external contamination of animals is the most widely considered explanation for rapid short-range dispersal or long-range dispersal over several hundred meters or kilometres (Barratt, Blossey, & Hokkanen, 2006). Several types of soil invertebrates have potential to act as phoretic hosts for EPN, including earthworms (Campos-Herrera, Trigo, & Gutierrez, 2006;, isopods , predatory carabid beetles (Mertz, Agudelo, Sales, Rohde, & Moino, 2014) and termites (Zadji, Baimey, Afouda, Moens, & Decraemer, 2014). However, only insects capable of flight will result in significant displacement of EPN from the site of application.…”