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Stunt Nematodes--Everything You Need to Know to Identify These Pests

By Hank Becker
March 21, 2001

New information about the anatomy of microscopic worms called stunt nematodes could help scientists identify one or more of the 111 known species in this class of destructive pests.

Stunt nematodes (Tylenchorhynchus spp.) are among the most costly plant parasites. Overall, plant parasitic nematodes in the United States cause annual economic losses estimated at nearly $10 billion from decreased food, fiber and ornamental production.

Stunt nematodes damage the roots of field and vegetable crops. Once damaged, plants become exposed to many destructive soilborne microorganisms and pathogens. A major problem with determining the damage these nematodes cause is inadequate knowledge of their distinguishing characteristics, numbers, relationships and geographic distribution.

After several years of studying specimens and pertinent literature of all described stunt nematode species, Agricultural Research Service microbiologist Zafar A. Handoo--an expert on identifying nematodes at the ARS Nematology Laboratory, Beltsville, Md.-- recently completed an identification key. This is the first accurate, all-inclusive guide to diagnose and identify all known stunt nematode species. The research has been published in the Journal of Nematology.

Handoo examined and evaluated all the information on these species contained in the USDA Nematode Collection, one of the world's largest and most valuable archives of these worms. It contains information on thousands of nematode species important to agriculture. His compendium details the most important diagnostic characteristics of each stunt nematode species.

Handoo’s key is based on the overall morphology--the external features--of females, since males are not known in several species. In some cases, he used the differences in male reproductive organs. In his key, he identified the main characteristics useful in distinguishing species, such as the shape of the lip region and shape of the tail. Further studies are needed of the worm’s morphology, including scanning electron microscopy to magnify male and female nematodes from a broader range of habitats.

ARS is the chief scientific research agency of the U.S. Department of Agriculture.

Scientific contact: Zafar A. Handoo, ARS Nematology Laboratory, Beltsville, Md., phone (301) 504-6666, fax (301) 504-5589,