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Nature of a beet cyst nematode population suppression unraveled

The Issue

Tiny parasitic roundworms (nematodes) that typically feed on underground plant parts are responsible for an estimated $10 billion in crop damage in the U.S. Nonchemical management of these pathogens has progressed slowly. No biological control product against plant-parasitic nematodes has ever received California EPA registration. The lack of understanding of microbe-nematode interactions is perhaps the greatest impediment to significant progress. Nematode-suppressive soils are soil sites where conditions for nematode-caused crop damage are present, but where such damage does not occur or where it occurs at a much lower level than expected. These are often sites where biological control occurs naturally and plant-parasitic nematode populations are typically maintained below the economic threshold.

What Has ANR Done?

In one soil site at the UC Riverside Agricultural Experiment Station, the population of the beet cyst nematode (Heterodera schachtii) has been suppressed for more than a quarter of a century. The location has been the focus of a decade-long investigation into the nature and cause of the phenomenon. Cooperative research in the laboratories of Dr. J. Ole Becker (AES/CE) and Dr. James Borneman (AES) found that Dactylella oviparasitica was suppressing beet cyst nematodes. This fungal hyperparasite attacks developing juveniles, females and eggs of the nematodes, thereby diminishing their population development. Introduction of this fungus into other beet cyst nematode-infested soils caused similar population declines.

The Payoff

Model system for identifying and analyzing disease-suppressive soils

The identification of this nematode-destroying fungus and its demonstrated ability to establish suppression in other soils open the door for new management strategies to control beet cyst nematodes. These advances in identifying pathogen-suppressing microorganisms will provide the basis for the next generation of plant pathogen management and disease control products. Numerous students, postgraduates and visiting scientists have been trained during the course of this project, and presentations at grower meetings, PCA training sessions and clientele workshops emphasized the benefits of biological disease suppression. Newsletter articles and journal publications further helped to disseminate the information.

Clientele Testimonial

"Sugarbeet cyst nematodes are a major crop production constraint in California agriculture. Managing nematode populations ought to include taking advantage of their enemies. UCR's researchers are on the right track."
John Radewald, disease control consultant and emeritus CE Specialist


Supporting Unit:

Departments of Nematology and Plant Pathology, CNAS, UC Riverside
J. Ole Becker
Department of Nematology
UC Riverside

J. Borneman
Department of Plant Pathology
UC Riverside