https://www.crec.ifas.ufl.edu/extension/diaprepes/bibliography/PDF/BioCont381.pdf

Successes and failures in the use of parasitic nematodes for pest control

https://www.crec.ifas.ufl.edu/extension/diaprepes/bibliography/PDF/2BioCont381.pdf

Application technology and environmental considerations for use of entomopathogenic nematodes in biological control

Production and application technology is critical for the success of entomopathogenic nematodes (EPNs) in biological control. Production approaches include in vivo, and in vitro methods (solid or liquid fermentation). For laboratory use and small scale field experiments, in vivo production of EPNs appears to be the appropriate method. In vivo production is also appropriate for niche markets and small growers where a lack of capital, scientific expertise or infrastructure cannot justify large investments into in vitro culture technology. In vitro technology is used when large scale production is needed at reasonable quality and cost. Infective juveniles of entomopathogenic nematodes are usually applied using various spray equipment and standard irrigation systems. Enhanced efficacy in EPN applications can be facilitated through improved delivery mechanisms (e.g., cadaver application) or optimization of spray equipment. Substantial progress has been made in recent years in developing EPN formulations, particularly for above ground applications, e.g., mixing EPNs with surfactants or polymers or with sprayable gels. Bait formulations and insect host cadavers can enhance EPN persistence and reduce the quantity of nematodes required per unit area. This review provides a summary and analysis of factors that affect production and application of EPNs and offers insights for their future in biological insect suppression.

/pdf/entomopathogenic-nematode-production-and-application-1hnp5iaro8.pdf

Entomopathogenic nematode production and application technology

Entomopathogenic nematodes (genera Steinernema and Heterorhabditis) kill insects with the aid of mutualistic bacteria. The nematode-bacteria complex is mass produced for use as biopesticides using in vivo or in vitro methods, i.e., solid or liquid fermentation. In vivo production (culture in live insect hosts) is low technology, has low startup costs, and resulting nematode quality is high, yet cost efficiency is low. In vitro solid culture, i.e., growing the nematodes and bacteria on crumbled polyurethane foam, offers an intermediate level of technology and costs. In vivo production and solid culture may be improved through innovations in mechanization and streamlining. In vitro liquid culture is the most cost-efficient production method but requires the largest startup capital and nematode quality may be reduced. Liquid culture may be improved through progress in media development, nematode recovery, and bioreactor design. A variety of formulations is available to facilitate nematode storage and application.

Production technology for entomopathogenic nematodes and their bacterial symbionts.

Summary 1. Entomopathogenic nematodes can function as indirect defence for plants that are attacked by root herbivores. By releasing volatile organic compounds (VOCs), plants signal the presence of host insects and thereby attract nematodes. 2. Nonetheless, how roots deploy indirect defences, how indirect defences relate to direct defences, and the ecological consequences of root defence allocation for herbivores and plant biomass are essentially unknown. 3. We investigate a natural below-ground tritrophic system, involving common milkweed, a specialist root-boring beetle and entomopathogenic nematodes, and asked whether there is a negative genetic correlation between direct defences (root cardenolides) and indirect defences (emission of volatiles in the roots and nematode attraction), and between constitutive and inducible defences. 4. Volatiles of roots were analysed using two distinct sampling methods. First, we collected emissions from living Asclepias syriaca roots by dynamic headspace sampling. This method showed that attacked A. syriaca plants emit five times higher levels of volatiles than control plants. Secondly, we used a solid phase micro-extraction (SPME) method to sample the full pool of volatiles in roots for genetic correlations of volatile biosynthesis. 5. Field experiments showed that entomopathogenic nematodes prevent the loss of biomass to root herbivory. Additionally, suppression of root herbivores was mediated directly by cardenolides and indirectly by the attraction of nematodes. Genetic families of plants with high cardenolides benefited less from nematodes compared to low-cardenolide families, suggesting that direct and indirect defences may be redundant. Although constitutive and induced root defences traded off within each strategy (for both direct and indirect defence, cardenolides and VOCs, respectively), we found no trade-off between the two strategies. 6. Synthesis. Constitutive expression and inducibility of defences may trade off because of resource limitation or because they are redundant. Direct and indirect defences do not trade off, likely because they may not share a limiting resource and because independently they may promote defence across the patchiness of herbivore attack and nematode presence in the field. Indeed, some redundancy in strategies may be necessary to increase effective defence, but for each strategy, an economy of deployment reduces overall costs.

http://www.eeb.cornell.edu/agrawal/documents/rasmannetal2001jecol.pdf

Direct and indirect root defences of milkweed (Asclepias syriaca): trophic cascades, trade‐offs and novel methods for studying subterranean herbivory

The ‘Oswego’ strain of Heterorhabditis bacteriophom has been demonstrated to be effective against several soil-inhabiting pests. This study examined factors affecting in vivo production of this entomopathogenic nematode in greater wax moth, Galleria mellonella , larvae. Timing of emergence of infective juveniles and total production was studied in relation to inoculum rate and host crowding. Nematode establishment increased with increasing inoculum rate in the range of 20–500 infective juveniles per host. However, total production per host was insensitive to inoculum rate within this range. Average number of infective juveniles produced was 336,000 per host. Production within environmental chambers was not influenced by crowding of hosts within production dishes, or crowding among dishes within the chamber. There was some evidence of a crowding effect within production dishes on total production when nematodes were reared in moderately fluctuating ambient laboratory temperatures (mean = 23.8°C). Large, late stage wax moth larvae produced 567,000 infective juveniles per host, twice as many as produced from small, late stage, wax moth larvae. Infective juveniles were produced in at least 3 emergence cycles, but the greatest proportion emerged in the 1st production cycle (82%). Median emergence time from inoculation to the midpoint of the 1st production cycle was 17 d at an inoculation rate of 20 infective juveniles per host. Median emergence time was 1-2 d faster at doses of 200 infective juveniles per host. Median emergence time also varied with location within the environmental chamber.

In Vivo Production of Heterorhabditis bacteriophora ‘Oswego’ (Rhabditida: Heterorhabditidae), a Potential Biological Control Agent for Soil-Inhabiting Insects in Temperate Regions

Field efficacy of 2 strains of entomopathogenic nematode, Heterorhabditis bacteriophora Poinar, were examined against alfalfa snout beetle larvae, Otiorhynchus ligustici (L.), in an established alfalfa field. Both strains were applied at 2.5 and 15 billion IJs per hectare using 2 different spray nozzle configurations. H. bacteriophora 'NC' reduced the insect larval population to 0.33-2.3 larvae per 54,900 cm 3 , significantly below the levels in the untreated controls, and reduced the incidence of snout beetle larval feeding and alfalfa stand death. NC occurred in 23-70% of the soil cores during the 1st growing season, but did not persist beyond the I st growing season. The high rate of H bcateriophora 'Oswego' reduced the insect larval population to 1.3 larvae per 54,900 cm 3 , significantly below the levels of the untreated controls but not as low as NC. Oswego also reduced the incidence of snout beetle larval feeding and alfalfa stand death. Oswego could be found in 73-99% of the soil cores during the 1st growing season and persisted for the entire 700 d of the trial. After 700 d, Oswego could be found in 24-44% of the soil cores taken within the treated plots. Evidence of nematode recycli ng was observed in both nematode strains. Data suggests that the NC strai n wou d be more appropriate in situations where a biopesticide is desired, and the Oswego strain is more appropriate where long-tern insect suppression is desired within more stable ecosystems.

Field Efficacy and Persistence of the Entomopathogenic Nematodes Heterorhabditis bacteriophora ‘Oswego’ and H. bacteriophora ‘NC’ on Alfalfa Snout Beetle Larvae (Coleoptera: Curculionidae)

Joan M. Miller

Papers

In Vivo Production of Heterorhabditis bacteriophora ‘Oswego’ (Rhabditida: Heterorhabditidae), a Potential Biological Control Agent for Soil-Inhabiting Insects in Temperate Regions

Field Efficacy and Persistence of the Entomopathogenic Nematodes Heterorhabditis bacteriophora ‘Oswego’ and H. bacteriophora ‘NC’ on Alfalfa Snout Beetle Larvae (Coleoptera: Curculionidae)