Influence of pesticides, soil temperature and moisture on entomopathogenic nematodes from southern Benin and control of underground termite nest populations

Abstract

The influence of three pesticides on the viability and infectivity of four Beninese isolates of entomopathogenic nematodes (EPN), Heterorhabditis indica Ayogbe1, H. sonorensis Azohoue2, H. sonorensis Ze3, and Steinernema sp. Bembereke, was determined. The impact of both soil temperature and soil moisture on the virulence of these EPN to Trinervitermes occidentalis was investigated in laboratory assays. The effect of EPN-infected Galleria mellonella larvae on underground populations of Macrotermes bellicosus was also examined. All tested Heterorhabditis species were more tolerant to glyphosate and fipronil than the Steinernema species. Heterorhabditis sonorensis Azohoue2, showed the best results with 63.2% termite mortality at a soil temperature of 35°C. The increase of soil moisture to 20% (w/w) did not negatively influence the virulence of tested EPN. The underground populations of 71% or 60% treated nests were controlled by H. sonorensis Azohoue2- or H. indica Ayogbe1-infected G. mellonella larvae, respectively.

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

“…But this method showed limitations as comeback is experienced after a period of time for some groups of termites that are capable of grooming new queen and king (Cubitermes and Macrotermes). Other nonchemical termite control methods include botanical termiticides [43], intercropping, crop rotation, planting of resistant crops [44], physical methods, i.e., debris removal, mechanical barriers, heat, high voltage electricity or electrocution, wood replacement, and biological control, i.e., use of predators [45], biological control agents such as fungi [46], bacteria, and nematodes [31,35]. In a partial review, Myles [47] reported 2 viruses, 5 bacteria, 17 fungi, 5 nematodes, and 4 mites that have the potential to kill termites; the full list of these organisms being no doubt larger.…”

“…Ten species of termites were found associated with citrus orchards in Benin: Amitermes guineensis, Ancistrotermes crucifer, Angulitermes truncates, Coptotermes intermedius, Cubitermes sp., M. bellicosus, Microcerotermes progrediens, Pericapritermes sp., Trinervitermes occidentalis, and Trinervitermes trinervius [30]. Among these, M. bellicosus, a fungus-growing termite, is the most important species that undermines citrus production and T. occidentalis, a grass-feeder termite, the most important to maize, cassava, groundnut, and bean grown under citrus canopies [31]. Abe et al [2] also reported that the most troublesome termites in agriculture are the fungus-growing termites.…”

“…For the same type of termites, El-Bassiouny et al [36] used El-Sebay's [37] modified trap. Baimey et al [31] broke at the top nests made by T. occidentalis and M. bellicosus in citrus orchards to collect directly workers and soldiers of the termites. Alternatively, these authors covered broken nests with dried straws.…”

“…Authors of Refs. [31,38] advised to put in the containers some moistened piece of paper as source of cellulose for the termites and also wet sand collected from termite nests. They also advised to keep the containers slightly open for aeration and in the dark at 25°C and 75-80% RH for 24 h before very active individuals are selected for experiments.…”

“…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.…”