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What Are Nematodes?
Nematodes are threadlike, microscopic, nonsegmented worms that feed predominantly in or on plant roots in virtually all environments in the world. There are approximately 4,000 known plant-parasitic nematode species. Depending on the species and its population level, damage to plants may range from mild to severe.
Nematode Threat
Nematodes are becoming an increasingly large threat to many crops. In 2004, the U.S. cotton industry alone lost an estimated $402 million—about 1,030,000 bales—to nematodes. Worldwide, nematodes are responsible for up to 14 percent of annual crop loss.
Nematode Damage
Nematodes damage crops by directly feeding on plant roots, transmitting viruses and/or facilitating bacterial and fungal infections. The feeding process can damage the roots of the plant, reducing its ability to absorb water and nutrients. A reduction of root mass, a distortion of root structure or enlargement of the roots may indicate the presence of nematodes. Symptoms of nematode damage intensify during stressful conditions such as excessively dry or wet weather. Furthermore, nematode damage provides an opportunity for other plant pathogens to invade the root and thus further weaken the plant.
Symptoms
Because nematode damage in crops is often unspecific, it is easily confused with drought, root feeding by other pests, malnutrition or disease. Typical symptoms are wilting despite sufficient soil moisture, yellowing of the foliage, uneven or stunted growth, and reduced root mass with or without galling. Since nematodes do not travel long distances, damage often appears in irregular, aggregated patches often elongated in the direction of the furrow. |
