Natural occurrence and distribution of entomopathogenic nematodes (Steinernematidae, Heterorhabditidae) in Viti Levu, Fiji Islands

Abstract

In Fiji, little or no attention has been given to entomopathogenic nematodes (EPNs) in biocontrol programs due to the lack of awareness about their occurrence and distribution in Fiji. A survey of EPNs was conducted for the first time in Fiji Islands in 2012 and 2013, throughout the eight provinces in Viti Levu to determine the occurrence and distribution across different habitat in Viti Levu. The soil samples from various habitats were collected and assayed for the presence of EPN using Galleria mellonella as baits. EPNs were recovered from five out of seven provinces with 35 positive sites (7.3%) out of 478 sites sampled. The only EPN genera encountered was Heterorhabditis. Steinernema was not isolated from any of the samples. Characterization of isolates was done by using morphometric and molecular examinations and isolates were identified as Heterorhabditis indica. H. indica isolates were primarily recovered from leeward side of the Viti Levu Island along the coastline and riversides, being more prevalent in lighter soil with pH > 6. Further, this study found significant association between habitat type, soil type, soil pH, average annual rainfall and EPN occurrence. This is the first record of naturally occurring EPNs in Fiji. The found nematodes will serve as the basis for efficacy screening with the ultimate aim of delivering effective, more sustainable and environmentally safe control for agricultural pests in Fiji.

Survey and identification of entomopathogenic nematodes in the province of Cotabato, Philippines, for biocontrol potential against the tobacco cutworm, Spodoptera litura (Fabricius) (Lepidoptera: Noctuidae)

“…From a total of 50 soil samples collected from peanut and grassland areas, only 5 harbored nematodes indicating a recovery rate of 10%. This low recovery rate is congruent with several previous studies on EPNs recovery in different surveys worldwide (Caoili et al 2018 andKour et al 2020). Several abiotic and biotic factors may likely influence the recovery of nematodes in the soil such as soil texture, moisture, pH, and vegetation (Abate et al 2018 andCampos-Herrera et al 2019).…”

A study on Xenorhabdus and Photorhabdus isolates from Northeastern Thailand: Identification, antibacterial activity, and association with entomopathogenic nematode hosts

“…The overall recovery rate of the EPNs ( Steinernema and Heterorhabditis ) from soil samples of Northeastern region of Thailand was 7.82%. This result was similar to that reported by Brodie [ 31 ] from Fiji Islands (7.3%), Valadas [ 32 ] from Portugal (6.7%), and Hatting [ 33 ] from South Africa (5%). However, this rate was higher than those reported by Caoili [ 34 ] from the Philippines (2.5%), Majić [ 35 ] from Croatia (2.0%), and Noujeim [ 36 ] from Lebanon (1%).…”

Ecological Characterisation of Native Isolates of Heterorhabditis indica from Viti Levu, Fiji Islands

“…In the present study, none of the isolates of H. indica showed nictating or vigorous jumping behaviour and showed strong directional response to volatile host cues confirming their cruiser behaviour. Even though, the IJ of native isolates of H. indica are longer ( Kour et al, 2020 ) than other isolates of H. indica described in literature, their foraging behaviour is similar to them ( Walia et al, 2008 ). However, this contradicts the finding of Susurluk et al (2003) who reported different foraging behaviour for isolates of same Heterorhabditis spp.…”

“…In the present study, we provide the ecology of the EPN H. indica isolated from the island of Viti Levu, Fiji. The native isolates of H. indica in this study have been isolated from different climatic zones and diverse habitats ( Kour et al, 2020 ). The isolated population of H. indica have shown some degree of morphometric and genetic variability ( Kour et al, 2020 ).…”

“…The native isolates of H. indica in this study have been isolated from different climatic zones and diverse habitats ( Kour et al, 2020 ). The isolated population of H. indica have shown some degree of morphometric and genetic variability ( Kour et al, 2020 ). Therefore, difference in activities or behaviour would be expected among these isolates.…”