Randy Gaugler

Entomopathogenic nematodes in biological control

Entomopathogenic Nematodes In Biological Control The most commonly studied entomopathogenic nematodes are of the families Heterorhabditidae and Steinernematidae, largely due to their efficacy as biological control agents (Gaugler 2006). Other... (PDF) Entomopathogenic nematodes in biological control Entomopathogenic nematode, Heterorhabditis bacteriophora, Microcerotermes diversus, Biological control One of the most common social insects documented in many countries around the world are termites, which are reported as economic and destructive pests, especially in Iraq. Entomopathogenic Nematodes as Potential Biological Control ... Entomopathogenic nematodes (EPN) are ubiquitous and generalized consumers of insects in soil food webs, occurring widely in natural and agricultural ecosystems on six continents. Augmentative releases of EPN have been used to enhance biological control of pests in agroecosystems. Potential for Entomopathogenic Nematodes in Biological ... Some of these entomopathogenic (insect-parasitic) nematodes are of considerable interest because of their potential as biological control agents of pest insects. If the nematode attacks an insect pest ; kills or hampers the development of the insect host; and is capable of mass production it can be used as an effective biological control agent. Nematodes as Biological Control Agents of Insects biological pest control using other organisms. ... Entomopathogenic nematodes (EPN) are microscopic, insect-killing roundworms comprising of a nematode-bacterium complex. The term entomopathogenic originates from the Greek word entomon (insect) and pathogenic, meaning disease-causing. EPNs are classified as entomopathogens because of the deadly ... Biological pest control – eco-friendly but lethal SA Grain Entomopathogenic nematodes are remarkably versatile in being useful against many soil and cryptic insect pests in diverse cropping systems, yet are clearly underutilized. Like other biological control agents, nematodes are constrained by being living organisms that require specific

Thermal adaptation of entomopathogenic nematodes: Niche breadth for infection, establishment, and reproduction

1. 1. We determined thermal niche breadths for infection, establishment, and reproduction of twelve species and strains of entomopathogenic nematodes collected from diverse climatic regions 2. 2. Steinernema riobravis infected Galleria mellonella (wax moth) larvae at the widest temperature range (10–39°C), whereas S. feltiae at the narrowest (8–30°C). Thermal niche breadt for establishment within hosts was the widest for S. glaseri, (10–37°C) and the narrowest for S. feltiae (8–30°C) 3. 3. Thermal niche breadth for reproduction was widest for S. glaseri (12–32°C) and the narrowest for S. carpocapsae (20–30°C). Steinernema scapterisci (20–32°C), S. riobravis (20–35°C), and Steinernema sp. (20–32°C) were more adapted to warm temperature reproduction, and S. feltiae to cooler temperatures (10–25°C) 4. 4. Although heterorhabditids are endemic to warmer climates, the upper thermal limits and temperature optima for reproduction of Heterorhabditis bacteriophora and H. megidis were cooler than that of some of the steinernematids from South America and the Caribbean 5. 5. Thermal niche breadths did not differ between conspecific populations isolated from different localities, but were different for different species isolated from the same locality 6. 6. We conclude that entomopathogenic nematode species have well-defined thermal niches which may be unaffected by their locality

Host finding behaviour as a predictor of foraging strategy in entomopathogenic nematodes

Foraging strategies of eight species of entomopathogenic nematodes were predicted from their response to host volatile cues and dispersal behaviour on 2-dimensional substrates. Positive directional response to chemical cues and similar distances travelled on smooth (agar) or nictation substrates (agar overlaid with sand grains) by Heterorhabditis bacterio-phora, Heterorhabditis megidis, Steinernema anomali , and Steinernema glaseri suggest their cruising approach to finding hosts. The absence of directional response and less distance travelled on nictation substrate, than on smooth agar by Steinernema carpocapsae and Steinernema scapterisci suggest their ambushing mode of foraging. Steinernema feltiae and Steinernema sp. responded directionally to host volatiles, but travelled less distance on the nictation substrate than on smooth agar; the two species also did not nictate. The cruiser species located hosts more effectively in the sand columns, whereas the ambushers were more effective at finding hosts on filter paper. Steinernema feltiae and Steinernema sp. performed equally on filter paper and in the sand column. We conclude that H. bacteriophora, H. megidis, S. anomali and S. glaseri cruise to find hosts, whereas S. carpocapsae and S. scapterisci ambush hosts. Steinernema feltiae and Steinernema sp. are intermediary in the search continuum sharing some characteristics of both ambush and cruise foragers.

Entomopathogenic nematode host finding : response to host contact cues by cruise and ambush foragers

Search behaviour of two entomopathogenic nematode species with different foraging strategies was compared by measuring parameters of unrewarded search after contact with host cues. Steinernema glaseri cruises in search of hosts. Steinernema carpocapsae ambushes hosts. Nematodes should respond to contact with relevant host cues by shifting their search from ranging to localized after contact with them. We predicted that cruising foragers rely on chemical cues more heavily than ambushers. These species were also tested for host affinities. Nematodes were tracked by image analysis after exposure to faeces, cuticle or food of either Popillia japonica or Spodoptera exiqua. Steinernema glaseri responded to selected host cues by shifting from ranging to localized search, characterized by decreased locomotory rate, distance travelled, search area and the proportion of the test period spent moving. Steinernema carpocapsae did not respond to host cues. Steinernema glaseri responds to selected chemical host cues for host location, whereas S. carpocapsae does not.

Effects of soil temperature, moisture, and relative humidity on entomopathogenic nematode persistence

Abstract Soil temperature, moisture, and relative humidity (RH) effects on the survival and pathogenicity of Steinernema carpocapsae and S. glaseri were tested in the laboratory. Survival and pathogenicity of S. carpocapsae were significantly greater at lower temperatures (5–25°C) than at the highest temperature (35°C). Conversely, S. glaseri survival and pathogenicity were significantly greater at higher temperatures (15–35°C) than at the lowest temperature (5°C). S. carpocapsae and S. glaseri survived best at low soil moistures of 2 and 4%, respectively. After rehydration by bringing up all tested moistures to 16%, both nematode species caused lethal infection of Galleria mellonella larvae. Survival and pathogenicity of these two nematode species decreased as RH decreased from 100 to 25% over the 32-day test period. At 100% RH, S. carpocapsae and S. glaseri survived for 32 days, but as RH was lowered, survival decreased. For example, at 25% RH, S. carpocapsae survived for 2 days and S. glaseri survived for only 4 hr. Pathogenicity was reinitiated after rehydration and showed a trend similar to survival. These differences in survival and pathogenicity may be attributed to the climatic origins or the soil habitats of these two nematode species.

Ecological considerations in the biological control of soil-inhabiting insects with entomopathogenic nematodes

Abstract Entomopathogenic nematodes in the families Steinernematidae and Heterorhabditidae are undergoing intense scrutiny as biological alternatives to chemicals for suppression of soil-inhabiting insects. Although naturally adapted to the soil, these nematodes are currently not as predictable or effective as chemical agents. Efforts to close or narrow this efficacy gap have been directed toward technological solutions, with striking advances being made recently in nematode mass rearing, shipping, storage, formulation and genetic improvement. Our understanding of entomopathogenic nematode soil ecology has not kept pace. In particular, we are unable to predict nematode behavior in the soil, biotic interactions with soil antagonists remain virtually unstudied, and the abiotic conditions optimal for survival and mobility are insufficiently understood. There is a compelling need for a standardized protocol that would permit cause and effect relationships to be established for successful and unsuccessful field trials. Fundamental to the applied use of entomopathogenic nematodes is gaining insight into nematode interactions with environmental parameters that determine the likelihood and outcome of nematode-insect encounters.

Nictation Behaviour and Its Ecological Implications in the Host Search Strategies of Entomopathogenic Nematodes (Heterorhabditidae and Steinernematidae)

[Entomopathogenic nematodes (Heterorhabditidae and Steinernematidae) are insect parasites that appear to use both cruising and ambushing search strategies. Cruising species Heterorhabditis bacteriophora, Steinernema feltiae, and S. glaseri spent more time crawling (88.8, 80.3, and 92.5% of observation period, respectively) and therefore traveled farther (22.4, 18.6, and 24.3 mm, respectively) and searched a larger area (18.3, 13.7, and 26.6 mm2, respectively) than ambushing species. Ambusher species S. carpocapsae and S. scapterisci traveled shorter distances (4.8 and 4.7 mm, respectively) and searched smaller areas (3.0 and 2.5 mm2, respectively) because they spent most of the observation period nictating (77.5 and 78.2%, respectively). Nictating infective juveniles raise greater than 95% of their body off the substrate and maintain a straight posture. A nictating species S. carpocapsae was up to 43 times as effective at finding mobile insect hosts compared to a non-nictating species H. bacteriophora. When unable to nictate host-finding of mobile insects declined from 35.7±7.19 to 3.9±1.11 infective juveniles per host. Nictation, by reducing the surface tension forces holding the nematode to the substrate, can increase the nematodes ability to attach to passing insects. S. carpocapsae also tended to search more effectively along a surface than through a matrix. Although entomopathogenic nematodes have a broad potential host range, differences in search behavior may result in a narrower actual host range. Ambushers being more specialized for mobile insects on the soil surface and cruisers for more sedentary and/or subterranean insects., Entomopathogenic nematodes (Heterorhabditidae and Steinernematidae) are insect parasites that appear to use both cruising and ambushing search strategies. Cruising species Heterorhabditis bacteriophora, Steinernema feltiae, and S. glaseri spent more time crawling (88.8, 80.3, and 92.5% of observation period, respectively) and therefore traveled farther (22.4, 18.6, and 24.3 mm, respectively) and searched a larger area (18.3, 13.7, and 26.6 mm2, respectively) than ambushing species. Ambusher species S. carpocapsae and S. scapterisci traveled shorter distances (4.8 and 4.7 mm, respectively) and searched smaller areas (3.0 and 2.5 mm2, respectively) because they spent most of the observation period nictating (77.5 and 78.2%, respectively). Nictating infective juveniles raise greater than 95% of their body off the substrate and maintain a straight posture. A nictating species S. carpocapsae was up to 43 times as effective at finding mobile insect hosts compared to a non-nictating species H. bacteriophora. When unable to nictate host-finding of mobile insects declined from 35.7±7.19 to 3.9±1.11 infective juveniles per host. Nictation, by reducing the surface tension forces holding the nematode to the substrate, can increase the nematodes ability to attach to passing insects. S. carpocapsae also tended to search more effectively along a surface than through a matrix. Although entomopathogenic nematodes have a broad potential host range, differences in search behavior may result in a narrower actual host range. Ambushers being more specialized for mobile insects on the soil surface and cruisers for more sedentary and/or subterranean insects.]

Soil type and entomopathogenic nematode persistence

Abstract Survival and pathogenicity of two entomopathogenic nematodes, Steinernema carpocapsae (= Neoaplectana ) and Steinernema glaseri , were tested in four types of soil: sand, sandy loam, clay loam, and clay over a period of 16 weeks. Significant differences in the survival and pathogenicity of both nematodes occurred in all soil types. S. carpocapsae survival was 44.9, 38.8, 32.9, and 26.7% in sandy loam, sand, clay loam, and clay, respectively, whereas S. glaseri survival was 30.1, 25.9, 22.5, and 19.3% in sand, sandy loam, clay loam, and clay, respectively, at the end of the test. S. glaseri survival was significantly lower than S. carpocapsae in all soil types. Survival for S. carpocapsae was greatest in sandy loam, while survival for S. glaseri was best in sand. Pathogenicity assays with recovered nematodes supported the survival data. Persistence of both species decreased as the proportion of clay increased.

Field efficacy of BG-Sentinel and industry-standard traps for Aedes albopictus (Diptera: Culicidae) and West Nile virus surveillance.

ABSTRACT Standard surveillance traps in North America for adult Aedes albopictus (Skuse) (Diptera: Culicidae), an invasive mosquito with public health implications, are currently ineffective. We compared the efficacy of the BG-Sentinel trap (BGS) with and without lures (BG-lure, octenol, and CO2), the Centers for Disease Control and Prevention light trap (CDC) with and without lures, and the gravid trap (GT) for Ae. albopictus collection in two urban sites in New Jersey. The BGS with or without lures collected more Ae. albopictus compared with other trap configurations and was more specific for Ae. albopictus. In Camden County, the BGS with lures collected three times more Ae. albopictus than the CDC (with CO2 only) and five times more than the GT. In Mercer County, BGS with lures collected the most mosquitoes, with 3 times more Ae. albopictus than the CDC with all lures and 50 times more than the GT. The BGS collected more male Ae. albopictus than other traps in both counties, providing further population monitoring. The GT and BGS provided a relative measure of the enzootic activity of West Nile virus in Culex spp. and the potential epidemic activity of WNV in Ae. albopictus. The BGS provides effective chemical and visual cues for host-seeking Ae. albopictus and should be used as a part of existing surveillance programs and new initiatives targeting this mosquito.

Production technology for entomopathogenic nematodes and their bacterial symbionts.

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. Journal of Industrial Microbiology & Biotechnology (2002) 28, 137–146 DOI: 10.1038/sj/jim/7000230