Pathogenicity ofHeterorhabditisnematodes isolated from north-western Himalaya against the larvae ofPlutella xylostella(L.) (Lepidoptera: Plutellidae)

Abstract

The efficacy of three entomopathogenic nematodes (Heterorhabditis spp.), from north western Himalaya, India was studied against the diamondback moth, Plutella xylostella (Linnaeus, 1758) (Lepidoptera: Plutellidae), under laboratory conditions. The larvae were exposed to 10, 20, 30 and 40 infective juveniles (IJs) of each nematode species for different time periods and they were found to be susceptible to all the EPNs tested. However, the susceptibility of larvae to nematode infection varied according to the dosages of IJs and their exposure periods. The efficacy of these indigenous entomopathogenic nematodes was also evaluated against the commercially available entomopathogenic nematode H. indica. An indigenous isolate, H. bacteriophora (HRJ), along with the commercial isolate H. indica recorded 100.0% mortality of insect larvae in 96 h exposure time against third instar larvae of P. xylostella. However, it was noticed that with the advancement of larval stage its mortality rate reduces and vice versa with the exposure period. All the tested nematode species were also found to reproduce within the host and produced infective juveniles. In conclusion, the evidence obtained in this study suggests that all the three indigenous EPN species are virulent enough to produce 100% mortality of larvae of P. xylostella. These EPN species thus have potential for the management of P. xylostella under integrated management practices. Résumé. Pathogénicité des nématodes Heterorhabditis isolés du nord-ouest de l'Himalaya contre les larves de Plutella xylostella (L.) (Lepidoptera : Plutellidae). L'efficacité de trois Nématodes entomopathogènes (Heterorhabditis spp.), du nord-ouest de l'Himalaya, en Inde, a été étudiée contre la Teigne des Crucifères, Plutella xylostella (Linnaeus, 1758), dans les conditions de laboratoire. Les larves ont été exposées à 10, 20, 30 et 40 juvéniles infectieux (JI) de chaque espèce de nématodes pendant différentes périodes. Elles ont été jugées sensibles à tous les nématodes entomopathogènes testés. Cependant, la sensibilité des larves à l'infection par les nématodes variait selon la doses de JI et le temps d'exposition. L'efficacité de ces nématodes entomopathogènes indigènes a également été évaluée par rapport à celle du nématode entomopathogène disponible dans le commerce, H. indica. Avec un temps d'exposition de 96 h des larves du troisième stade de P. xylostella, l'isolât indigène H. bacteriophora, ainsi que l'isolât commercial H. indica, ont entraîné une mortalité de 100% des larves d'insectes. Cependant, il a été remarqué qu'avec l'avancement de la phase larvaire, le taux de mortalité diminue et le temps d'exposition nécessaire augmente. Toutes les espèces de nématodes testées se sont également retrouvées dans l'hôte et ont produit des juvéniles infectieux. En conclusion, les preuves obtenues dans cette étude suggèrent que les trois espèces de nématodes entomopathogènes indigènes sont suffisamment virulentes pour entraîner 100% de mortalité des larves de P. xylostella. Ces espèces ont donc un i...

Evaluation of indigenous entomopathogenic nematodes in Southwest China as potential biocontrol agents against Spodoptera litura (Lepidoptera: Noctuidae)

“…While developing a durable management strategy for inundative release of EPNs against local pest insects, indigenous nematodes are more suitable because of their adaptation to local climate and host population ( Bedding, 1990 ). Thus, exploration of indigenous EPN is pivotal for EPN application in certain area; surveys conducted around the world demonstrated widespread occurrence and provided wide information on the indigenous species and populations of EPNs and their virulence to the target insect pest ( Vashisth et al, 2017 ). For example, several commercial EPNs were tested to control Popillia japonica detected in Northern Italy in 2014 with variable results ( Marianelli et al, 2018 ), and thus the dire need for locally and adapted populations of EPNs is well-recognized.…”

Potential of Entomopathogenic Nematode HbSD as a Candidate Biocontrol Agent against Spodoptera frugiperda

“…As EPNs are predominantly isolated from soil habitats, they have been extensively exploited to suppress soil-dwelling insect pests in agricultural fields. Recently, the foliar applications of EPN biocontrol have been reported for the targeting of several lepidopteran pests, such as Tortricidae, Plutelidae, Gelechiidae and Erebidae [ 36 , 37 , 38 , 39 , 40 ]. To widen the utilization of EPN for biocontrol, isolating and screening more EPN species/strains that meet the efficacy requirements is the first pivotal step.…”