B. A. Jaffee

Bio: B. A. Jaffee is an academic researcher from University of California, Davis. The author has contributed to research in topics: Nematophagous fungus & Nematode. The author has an hindex of 18, co-authored 25 publications receiving 792 citations.

Nematode-Trapping Fungi in Organic and Conventional Cropping Systems

Abstract: Jaffee, B. A., Ferris, H., and Scow, K. M. 1998. Nematode-trapping fungi in organic and conventional cropping systems. Phytopathology 88:344350. Nematode-trapping fungi, nematodes, and microbial biomass were quantified in conventionally and organically managed field plots in the Sustainable Agriculture Farming Systems Project at the University of California at Davis. There were four replicate plots (0.135 ha per plot) for each management system, and plots were sampled three times each year for 2 years. The hypothesis that nematode-trapping fungi would be more abundant in organically managed plots was partially supported: the number of species of nematode-trapping fungi was slightly but significantly greater in organic than in conventional plots, two species ( Arthrobotrys dactyloides and Nematoctonus leiosporus) were detected more frequently in organic plots, and the population dens ities of A. dactyloides and N. leiosporus were greater in organic than in conventional plots. Two other species (A. haptotyla and A. thaumasia), however, tended to be more numerous in conventional than in organic plots, and the total density of nematode-trapping fungi was similar in organic and conventional plots. Bacterivorous nematodes were more abundant and microbial biomass (substrate-induced respiration) was greater in organic than in conventional plots. Suppression of the root-knot nematode Meloidogyne javanica, as measured in a bioassay, was not related to management system or population density of nematode-trapping fungi but was positively related to microbial biomass.

Nematode-trapping fungi of a natural shrubland: Tests for food chain involvement

Abstract: We describe the spatial and temporal pat- terns in the abundance of nematode-trapping fungi and in suppression of nematodes in a coastal shrub- land. A previous study at this location (Bodega Ma- rine Reserve, Sonoma County, California) had doc- umented a soil food chain in which an insect-parasitic nematode consumes and kills the soil-dwelling larva of the ghost moth, which otherwise consumes and kills the bush lupine; the patchy distribution of the nematode and lupine suggest the involvement of ne- matophagous organisms, including nematode-trap- ping fungi. To test our model (trapping fungi kill insect-parasitic nematodes, and therefore ghost moths persist and kill lupines at some sites), we hy- pothesized that sites with substantial lupine mortality would contain larger numbers of nematode-trapping fungi and would be more suppressive to nematodes than would sites with little lupine mortality. Soil was collected from eight sites (four with substantial lu- pine mortality and four with little lupine mortality) at 2-mo intervals for 1 yr and subjected to dilution plating and most probable number procedures. Nematode-trapping fungi detected were Arthrobotrys brochopaga, A. musiformis, A. oligospora, A. superba, Geniculifera paucispora, Hirsutella rhossiliensis, Mon- acrosporium cionopagum, M. doedycoides, M. euder- matum, M. parvicollis, Nematoctonus concurrens, and Stylopage sp. A. oligospora was the most abundant. Some soil samples contained large numbers of nem- atode-trapping fungi (as many as 695 propagules/g of soil), but sites with substantial lupine mortality did not contain larger numbers than did sites with little mortality. In a laboratory bioassay, suppression of the

Strong bottom-up and weak top-down effects in soil: nematode-parasitized insects and nematode-trapping fungi

Abstract: The soils of the Bodega Marine Reserve (BMR, Sonoma County, California) contain many nematode-trapping fungi and many ghost moth larvae parasitized by entomopathogenic nematodes. The current study determined whether these nematode-parasitized moth larvae, which can produce very large numbers of nematodes, enhanced the population densities of nematode-trapping fungi and whether the fungi trapped substantial numbers of nematodes emerging and dispersing from moths. Wax moths were used in place of ghost moths because the former are easier to obtain. When nematode-parasitized moth larvae were added to laboratory microcosms containing BMR field soil, the population densities of four nematode-trapping fungi increased substantially. The greatest increase in population density was by Arthrobotrys oligospora, which uses adhesive networks to capture nematodes. A. oligospora population density increased about 10 times when the added moth larvae were parasitized by the nematode Heterorhabditis marelatus and about 100 times when added moth larvae were parasitized by the nematode Steinernema glaseri. Other trapping fungi endemic to the soil and enhanced by nematode-parasitized moth larvae included Myzocytium glutinosporum, Drechslerella brochopaga, and Gamsylella gephyropaga, which produce adhesive spores, constricting rings, and adhesive branches, respectively. The data suggest that the previously documented abundance and diversity of nematode-trapping fungi in BMR soil can be explained, at least in part, by nematode-parasitized insects, although that inference requires further studies with ghost moths. The strong bottom-up enhancement of nematode-trapping fungi was not matched by a strong top-down suppression of nematodes, i.e. the fungi trapped fewer than 30% of dispersing nematodes.

Susceptibility of root knot and cyst nematodes to the nematode-trapping fungi Monacrosporium ellipsosporum and M. cionopagum

Abstract: We compared the susceptibility of Meloidogyne javanica and Heterodera schachtii to the nematode-trapping fungi Monacrosporium ellipsosporum and M. cionopagum . The fungi were added in the form of fungal-colonized nematodes or hyphae pelletized in alginate to field soil in small vials. Suppression by the fungi was measured by comparing nematode invasion of roots in fungal treated and untreated soil. Meloidogyne javanica was much more susceptible than H. schachtii to both fungi, regardless of the form of fungal inoculum. Thus, when colonized nematodes were used as fungal inoculum, suppression of M. javanica and H. schachtii was 92 and 6% by M. ellipsosporum and 54 and 0% by M. cionopagum . Similarly, when pelletized hyphae were used, suppression of M. javanica and H. schachtii was 80 and 10% by M. ellipsosporum and 98 and 24% by M. cionopagum . In other tests, two additional populations of H. schachtii were relatively resistant and two additional species of root-knot nematode, M. incognita and M. chitwoodi , were relatively susceptible to these fungi. The results indicate that Meloidogyne spp in general are more susceptible than H. schachtii to M. ellipsosporum and M. cionopagum .

Higher-order predators and the regulation of insect herbivore populations

Abstract: ▪ Abstract Empirical research has not supported the prediction that populations of terrestrial herbivorous arthropods are regulated solely by their natural enemies. Instead, both natural enemies (top-down effects) and resources (bottom-up effects) may play important regulatory roles. This review evaluates the hypothesis that higher-order predators may constrain the top-down control of herbivore populations. Natural enemies of herbivorous arthropods generally are not top predators within terrestrial food webs. Insect pathogens and entomopathogenic nematodes inhabiting the soil may be attacked by diverse micro- and mesofauna. Predatory and parasitic insects are attacked by their own suite of predators, parasitoids, and pathogens. The view of natural enemy ecology that has emerged from laboratory studies, where natural enemies are often isolated from all elements of the biotic community except for their hosts or prey, may be an unreliable guide to field dynamics. Experimental work suggests that interactions ...

Rhizosphere interactions and the exploitation of microbial agents for the biological control of plant-parasitic nematodes.

Abstract: A range of specialist and generalist microorganisms in the rhizosphere attacks plant-parasitic nematodes. Plants have a profound effect on the impact of this microflora on the regulation of nematode populations by influencing both the dynamics of the nematode host and the structure and dynamics of the community of antagonists and parasites in the rhizosphere. In general, those organisms that have a saprophytic phase in their life cycle are most affected by environmental conditions in the rhizosphere, but effects on obligate parasites have also been recorded. Although nematodes influence the colonization of roots by pathogenic and beneficial microorganisms, little is known of such interactions with the natural enemies of nematodes in the rhizosphere. As nematodes influence the quantity and quality of root exudates, they are likely to affect the physiology of those microorganisms in the rhizosphere; such changes may be used as signals for nematode antagonists and parasites. Successful biological control strategies will depend on a thorough understanding of these interactions at the population, organismal, and molecular scale.