Dispersal and Repulsion of Entomopathogenic Nematodes to Prenol

Journal of chemical ecology, 2016

Recent work has shown the potential for enhanced efficacy of entomopathogenic nematodes (EPN) through their attraction to herbivore induced plant volatiles. However, there has been little investigation into the utilization of these attractants in systems other than in those in which they were identified. We compared (E)-β-caryophyllene and pregeijerene in the highbush blueberry (Vaccinium corymbosum) agroecosystem in their ability to enhance the attraction of EPN to and efficacy against the system's herbivore, oriental beetle (Anomala orientalis). The relative attractiveness of (E)-β-caryophyllene and pregeijerene to a local isolate of the EPN species Steinernema glaseri was tested in a six-arm olfactometer in the laboratory to gather baseline values of attraction to the chemicals alone in sand substrate before field tests. A similar arrangement was used in a V. corymbosum field by placing six cages with assigned treatments and insect larvae with and without compound into the so...

Journal of Invertebrate Pathology, 2011

Laboratory experiments were conducted on the behavioral responses of five species of entomopathogenic nematodes (EPNs; Steinernema diaprepesi, Steinernema sp. glaseri-group, Steinernema riobrave, Heterorhabditis zealandica, Heterorhabditis indica) to three species of nematophagous fungi (NF; trapping fungus Arthrobotrys gephyropaga; endoparasites Myzocytium sp., Catenaria sp.). We hypothesized that EPN responses to NF and their putative semiochemicals might reflect the relative susceptibility of EPNs to particular NF species. EPN responses to ''activated'' NF (i.e., induced to form traps or sporangia by previous interactions with nematodes) versus controls of non-activated NF or heat-killed EPNs were compared in choice experiments on water agar in Petri dishes (dia = 9 cm) and in horizontal sand columns (8 cm L Â 2.7 cm dia). On agar, all EPN species were attracted to all activated NF species except for S. riobrave, which was neutral. In sand, all EPN species were repelled by activated Arthrobotrys but attracted to activated Myzocytium and Catenaria, except H. indica (neutral to Myzocytium) and Steinernema sp. (neutral to Catenaria). EPN behavioral responses appeared unrelated to relative susceptibility to NF except that H. indica exhibited low susceptibility and a neutral response to Myzocytium in sand whereas the remaining EPNs were highly susceptible and attracted. These results indicate potential complexity (i.e., mixed responses, aggregation or group movement) and species specificity in the responses of EPNs to NF, demonstrate that results on agar can differ markedly from those in sand, and underline the potential importance of utilizing natural substrates to properly assess the role of semiochemicals in nematode-fungus interactions.

Archives of Phytopathology and Plant Protection, 2018

Biocontrol potential of the entomopathogenic nematodes (EPNs) on the second-instar larvae of the non-target insect predators, Coccinella septumpunctata and Chrysoperla carnea as compared to Spodoptera littoralis (Boisd.) was evaluated. The pathogenicity of EPNs, namely, Heterorhabditis bacteriophora, Steinernema feltiae and Steinernema carpocapsae at concentrations 100, 200, 400, 800 and 1600 IJs/cup) were tested at 2, 4 and 6 days' postinoculation. Laboratory results showed significant differences among the mortality rates of different tested larvae, for each concentration at different time intervals. H. bacteriophora induced the highest mortality followed by S. carpocapsae treatment. However, S. feltiae was found to be more safety on predators as it causes less mortality at 6 days of treatment. The values of half lethal concentrations (LC 50) were 614.06, 3797.43 and 676.47 IJs/cup for C. Carnea and 390.60, 1209.88 and 503.65 IJs/cup for C. septumpunctata treated by H. bacteriophora, S. feltiae and S. carpocapsae, respectively. In semi-field experiments, there were non-significant differences among mortality of each predator indicated at concentrations of the different EPNs after 2 days or 6 days' post-inoculation. The study revealed a lethal pathogenic effect of EPNs against insect pests but caused low mortality on the non-target ones.

Ecological Entomology, 2014

1. Top-down population regulation can influence the success of biological control agents when they are released into the field. Entomopathogenic nematodes (EPNs) are used commonly in biological control programmes, but their efficacy suffers from poor persistence. Although abiotic soil conditions have been shown to reduce EPN persistence, consumption of infected insects by scavengers and of infective juvenile (IJ) nematodes by predators may also regulate these populations. In the present study, the effects of different soil arthropods on EPNs in laboratory conditions were measured. It was hypothesised that arthropods commonly found in soil communities where EPNs are applied would consume cadavers of insects parasitised by the nematodes and the IJs themselves. 2. Some species of scavengers consume EPN-infected insects. Crickets (Gryllus bimaculatus De Geer), American cockroaches [Periplaneta Americana (Linnaeus)], ants [Tetramorium chefketi Forel and Pheidole pallidula (Nylander)], earwigs (Labidura riparia Pallas), mites (Sancassania polyphyllae Zachvatkin), and springtails (Sinella curviseta Brook and Folsomia candida Willem) have different responses to nematode-killed insects. Results suggested that ants (T. chefketi), cockroaches, mites, and earwigs fed on Steinernema-killed insects whereas neither crickets nor springtails consumed them. 3. In the second part of the study, experiments were conducted to determine whether mites and springtails consumed IJ EPNs. Results showed that S. polyphyllae mites do not consume infective juveniles in soil, whereas both springtail species consumed significant numbers of the IJs. 4. Top-down regulatory processes can be a limiting factor for EPN populations under laboratory conditions. Both host cadavers and IJs are consumed (albeit by different arthropods), so these results may help explain the difficulties associated with the persistence of EPN application to soil.

Chemoecology, 2017

Diaprepes abbreviatus is an invasive pest of citrus in the USA from the Caribbean. Entomopathogenic nematodes (EPNs) are used as biological control agents in citrus agroecosystems against D. abbreviatus. EPNs respond to herbivore-induced volatiles from citrus roots to assist in the location of insect hosts. Here, we investigated EPN response to the male-produced sex pheromone of D. abbreviatus. In the laboratory, we used two-choice tests to investigate the behavioral response of Steinernema diaprepesi, Heterorhabditis indica, Steinernema riobrave, and the plant parasitic nematode, Tylenchulus semipenetrans, to the synthetic sex pheromone of D. abbreviatus, as well as its natural source, beetle frass. Nematodes were not attracted by volatiles of citrus plant origin or carvacrol, a non-pheromone volatile associated with beetle frass. S. diaprepesi and H. indica were attracted to the frass and the pheromone of D. abbreviatus. The response of S. diaprepesi to the pheromone was greater than that of H. indica at all doses tested; the greatest response from both species occurred at 0.12 and 1.2 ng of pheromone/lL of solvent. Deploying the pheromone in a citrus grove increased the mortality of caged Diaprepes larvae as compared to control larvae deployed with solvent alone. Also, more EPNs were found in the soil surrounding the pheromone-baited larvae than the surrounding controls.

PLoS ONE, 2012

While the role of herbivore-induced volatiles in plant-herbivore-natural enemy interactions is well documented aboveground, new evidence suggests that belowground volatile emissions can protect plants by attracting entomopathogenic nematodes (EPNs). However, due to methodological limitations, no study has previously detected belowground herbivore-induced volatiles in the field or quantified their impact on attraction of diverse EPN species. Here we show how a belowground herbivore-induced volatile can enhance mortality of agriculturally significant root pests. First, in real time, we identified pregeijerene (1,5-dimethylcyclodeca-1,5,7-triene) from citrus roots 9-12 hours after initiation of larval Diaprepes abbreviatus feeding. This compound was also detected in the root zone of mature citrus trees in the field. Application of collected volatiles from weevil-damaged citrus roots attracted native EPNs and increased mortality of beetle larvae (D. abbreviatus) compared to controls in a citrus orchard. In addition, field applications of isolated pregeijerene caused similar results. Quantitative real-time PCR revealed that pregeijerene increased pest mortality by attracting four species of naturally occurring EPNs in the field. Finally, we tested the generality of this root-zone signal by application of pregeijerene in blueberry fields; mortality of larvae (Galleria mellonella and Anomala orientalis) again increased by attracting naturally occurring populations of an EPN. Thus, this specific belowground signal attracts natural enemies of widespread root pests in distinct agricultural systems and may have broad potential in biological control of root pests.

Molecular Plant, 2020

Biological Control, 2006

We discuss the behavior and ecology of entomopathogenic nematodes in relation to their successes and failures as biological control agents. Four categories of studies have been reviewed herein; infective juvenile foraging strategies, recognition and evaluation of the host by infective juveniles, the actual behaviors of infective juveniles that result in infection, and the protective role of the symbiotic bacteria during nematode reproduction in the cadaver. This constitutes a chronological order of events. Two challenges are suggested. First, the data on entomopathogenic nematode behavioral ecology, while very extensive for some species, are almost completely lacking for most described species. We need to approach future studies paying more attention to phylogenetic origins of the traits that we study. Second, there is little consensus on exactly what are the traits that are worth studying. By reviewing and synthesizing current work, we make some suggestions about where future research should be directed.

Journal of Ecology, 2011

1. Indirect plant defences are well documented for the above-ground constituents of plants.

International Journal of Advanced Research in Biological Sciences (IJARBS), 2017

Safety and environmentalcal insecticide issues surrounding the use of chemical insecticides has led to an emphasis on developing alternative control measures such as entomopathogens and their products. Entomopathogenic nematodeare effective biopesticide which can be incorporated in IPM programs because they are considered non-toxic to humans, relatively specific to their target pests and can be applied with standard pesticide equipment. Entomopthogenic nematodes have proven to be the most effective as biological control organisms. Entomopathogenic nematodes have been released extensively in crop fields with negligible effects on non target insects and are regarded as exceptionally safe to the environment. Our focus in this paper was to review mechanism and pathogencity of nematode, phylogeny of nematode for Steinernematidae and Heterorhabditidae. Steinernematidae is represented by the genera Steinernema and Neosteinernema and Heterorhabditidae is represented by the genus Heterorhabditis. They are associated with mutualistic bacteria in the genus Xenorhabdus for Steinernema and Photorhabdus for Heterorhabditis. Thus, it is a nematode bacterium complex that works together as a biological control unit to kill an insect host by penetrating the host through natural opening and there by releasing the bacterial symbiont which spread and multiply in the haemolymph of the insect pest and kill them by septicemia. Infective juvenile entomopathogenic nematode locate their hosts in soil by means of two strategies-ambusing and crusing. Nematode employs different foraging strategies to locate and infect hosts. Genetic diversity may be lost, or genetic variation may have been limited during collection or lost during importation and rearing. A serious problem for EPNs is founder effect because only a limited number of insect cadavers are collected at single geographical sites, resulting in reduced genetic variance. EPNs have been most efficacious in habitats that provide protection from environmental extremes, especially in soil, which is their natural habitat and in cryptic habitats. Excellent control has been archived against plantboring insects because their cryptic habitats are favorable for nematode survival and infectivity. In developing biocontrol programs using EPNs, one mechanism to increase the chance of success is to screen novel nematode species or strains for potential efficacy against particular target pests.