Density‐dependent parasitism in biological control of soil‐borne insects, nematodes, fungi and bacteria

Jaffee, B. A.

doi:10.1080/09583159309355279

Cited by 16 publications

(11 citation statements)

References 65 publications

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“…On a continuum from facultative to obligatory parasitism, A. oligospora tends to be a strong saprophyte, while M. gephyropaga and A. musiformis are more inclined to nematophagy and Catenaria sp. is primarily parasitic (Jaffee, 1993;Jansson, 1982). A saprophytic response to insect cadavers would more likely be detected by measuring fungi from soil as in Jaffee and Strong (2005) than by measuring fungi from nematode samples as was done in our survey.…”

Section: Discussionmentioning

confidence: 96%

Wide interguild relationships among entomopathogenic and free-living nematodes in soil as measured by real time qPCR

Campos‐Herrera

El-Borai

Duncan

2012

Journal of Invertebrate Pathology

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Entomopathogenic nematodes (EPNs) are promising biological control agents of soil-dwelling insect pests of many crops. These nematodes are ubiquitous in both natural and agricultural areas. Their efficacy against arthropods is affected directly and indirectly by food webs and edaphic conditions. It has long been suggested that a greater understanding of EPN ecology is needed to achieve consistent biological control by these nematodes and the development of molecular tools is helping to overcome obstacles to the study of cryptic organisms and complex interactions. Here we extend the repertoire of molecular tools to characterize soil food webs by describing primers/probe set to quantify certain free-living, bactivorous nematodes (FLBNs) that interact with EPNs in soil. Three FLBN isolates were recovered from soil baited with insect larvae. Morphological and molecular characterization confirmed their identities as Acrobeloides maximum (RT-1-R15C and RT-2-R25A) and Rhabditis rainai (PT-R14B). Laboratory experiments demonstrated the ability of these FLBNs to interfere with the development of Steinernema diaprepesi, Steinernema riobrave and Heterorhabditis indica parasitizing the weevil Diaprepes abbreviatus (P<0.001), perhaps due to resource competition. A molecular probe was developed for the strongest competitor, A. maximum. We selected the highly conserved SSU rDNA sequence to design the primers/probe, because these sequences are more abundantly available for free-living nematodes than ITS sequences that can likely provide better taxonomic resolution. Our molecular probe can identify organisms that share ⩾98% similarity at this locus. The use of this molecular probe to characterize soil communities from samples of nematode DNA collected within a citrus orchard revealed positive correlations (P<0.01) between Acrobeloides-group nematodes and total numbers of EPNs (S. diaprepesi, H. indica and Heterorhabditis zealandica) as well as a complex of nematophagous fungi comprising Catenaria sp. and Monachrosporium gephyropagum that are natural enemies of EPNs. These relationships can be broadly interpreted as supporting Linford's hypothesis, i.e., decomposition of organic matter (here, insect cadavers) greatly increases bactivorous nematodes and their natural enemies.

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Section: Discussionmentioning

confidence: 96%

Wide interguild relationships among entomopathogenic and free-living nematodes in soil as measured by real time qPCR

Campos‐Herrera

El-Borai

Duncan

2012

Journal of Invertebrate Pathology

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“…Moreover, Model II shows that sterilization confers no competitive disadvantage within a population, and so a sterilizing virus might persist for a long time following strategic release. This would at least allow the possibility of control of rabbits by inundative release of the sterilizing virus ( sensu Jaffee 1993) if the classical biological control strategy fails.…”

Section: Discussionmentioning

confidence: 99%

Biological control using sterilizing viruses: host suppression and competition between viruses in non‐spatial models

Hood

Chesson

Pech

2000

Journal of Applied Ecology

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Summary 1.Research is currently underway to develop genetically engineered viruses that can sterilize pest animals. The technique, known as viral-vectored immunocontraception (VVIC), promises to control mammalian pests such as the European rabbit, the house mouse and domestic cats. 2. Using host±parasite models we explored the degree of control of the host population that can be attained when hosts that recover from infection become permanently infertile. The models assume some demographic compensation for reduced fertility in the host population, and are tailored to address issues raised by the use of the myxoma virus as an agent to sterilize rabbits. A`pay-o' function is developed, which de®nes the degree to which host density is suppressed by a sterilizing agent. 3. The results show that sterilizing viruses can reduce host abundance, and that hosts with low birth rates and moderate mortality rates are the best targets for VVIC. High transmissibility increases the pay-o from VVIC, but because virulent parasites kill most of the hosts that they infect, the pay-o is highest if benign parasites are used as the vector of contraceptive antigens. We argue that appropriate pay-o functions should be developed as a basis for research and development on genetically modi®ed organisms. 4. The host±parasite models are extended to include a competing strain of virus that does not sterilize the host. We analysed these models using a general approach to the analysis of competition, which has not often been applied to epidemiological models. The extended model shows that host sterilization per se does not aect the competitive ability of viruses, a result that applies to a broad class of models in which the per capita growth rates of competing parasites are linear functions of limiting competitive factors.

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“…The Dutch site contained the smallest numbers of Meloidogyne, perhaps insufficient to maintain or to allow the development of large populations of P. penetrans. The population density of obligate parasites is usually regulated by their host density (Ciancio 1995;Jaffee 1993), which allows an equilibrium in which both populations can co-exist (Anderson and May 1981). A P. penetrans population is, therefore, thought to be maintained as long as susceptible Meloidogyne spp.…”

Section: Microbial Enemy Diversity and Dynamicsmentioning

confidence: 99%

“…This phenomenon also occurs for Ammophila breviligulata in North America, and has been studied in parallel. Soil-borne pathogens and parasites, particularly plant-parasitic nematodes (PPN), are considered to be involved in both the die-back and successional decline of marram grass (Van der Putten et al 1988, 1993Van der Putten and Peters 1997). This has been demonstrated by glasshouse experiments where the application of fungicides and nematicides to marram grass seedlings growing in non-sterile soil promoted plant growth, suggesting the involvement of soil fungi and PPN in a disease complex of marram grass (de Rooij-van der Goes 1995; Van der Putten 1990).…”

Section: Introductionmentioning

confidence: 99%

Interactions between nematodes and their microbial enemies in coastal sand dunes

et al. 2012

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European foredunes are almost exclusively colonised by Ammophila arenaria, and both the natural succession and the die-out of this plant have been linked to populations of plant-parasitic nematodes (PPN). The overarching aim of this study was to investigate top-down control processes of PPN in these natural ecosystems through comparative analyses of the diversity and dynamics of PPN and their microbial enemies. Our specific aims were, first, to identify and quantify PPN microbial enemies in European sand dunes; second, to assess their life history traits, their spatial and temporal variation in these ecosystems, and third, to evaluate their control potential of PPN populations. This was done by seasonal sampling of a range of sites and making observations on both the nematode and the microbial enemy communities in rhizosphere sand. Nine different nematode microbial enemies belonging to different functional groups were detected in European sand dunes. Their high diversity in these low productivity ecosystems could both result from or lead to the lack of dominance of a particular nematode genus. The distribution of microbial enemies was spatially and temporally variable, both among and within sampling sites. Obligate parasites, either with low host-specificity or having the ability to form an environmentally resistant propagule, are favoured in these ecosystems and are more frequent and abundant than facultative parasites. Three microbial enemies correlated, either positively or negatively, with PPN population size: Catenaria spp., Hirsutella rhossiliensis and Pasteuria penetrans. Microbial-enemy supported links in the food-web may be involved in the control of PPN populations through indirect effects. The endospore-forming P. penetrans was the most successful top-down control agent, and was implicated in the direct control of Meloidogyne spp. and indirect facilitation of Pratylenchus spp. Overall, our findings suggest strong and diverse top-down control effects on the nematode community in these natural ecosystems.

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Density‐dependent parasitism in biological control of soil‐borne insects, nematodes, fungi and bacteria

Cited by 16 publications

References 65 publications

Wide interguild relationships among entomopathogenic and free-living nematodes in soil as measured by real time qPCR

Wide interguild relationships among entomopathogenic and free-living nematodes in soil as measured by real time qPCR

Biological control using sterilizing viruses: host suppression and competition between viruses in non‐spatial models

Interactions between nematodes and their microbial enemies in coastal sand dunes

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