Stubby-root nematodes feed on the roots of tomato plants and cause the roots to appear stunted and stubby. The curved stylet that stubby-root nematodes use to feed makes them unique, as other nematodes possess straight stylets. They feed primarily on root tips, causing elongation of roots to stop and making it more difficult for tomatoes to receive adequate water and nutrients. Symptoms of stubby-root nematodes are more severe in sandy soils and generally appear as odd-shaped patches.
Nematodes in the family Trichodoridae are commonly called "stubby-root" nematodes, because feeding by these nematodes can cause a stunted or "stubby" appearing root system. Paratrichodorus minor is the most common species of stubby-root nematode worldwide. Paratrichodorus minor is important because of the direct damage it causes to the plant roots, and also because it can transmit certain plant viruses.
Stubby-root nematodes are very small and can be seen only with the aid of a microscope. They are ectoparasitic nematodes, meaning that they feed on plants while their bodies remain in the soil. They feed primarily on meristem cells of root tips. Stubby-root nematodes are plant-parasitic nematodes in the Triplonchida, an order of nematodes characterized by having a six-layer cuticle (body covering). Stubby-root nematodes are unique among plant-parasitic nematodes because they have an onchiostyle, a curved, solid stylet or spear that is used in feeding. All other plant-parasitic nematodes have straight, hollow stylets.
Stubby-root nematodes use their onchiostyle like a dagger to puncture holes in plant cells. The stubby root nematode then secretes from its mouth (stoma) salivary material into the punctured cell. The salivary material hardens into a feeding tube which functions as a "straw" enabling the nematode to withdraw and ingest the cell contents through the tube. After feeding on an individual cell, the stubby-root nematode will move on to feed on other cells, leaving old feeding tubes behind and forming new ones in each cell that it feeds from.
Damage caused by P. minor usually occurs in irregularly shaped patches within a given field. Symptoms are usually more severe in sandy than in heavier soils. Above ground symptoms include; stunting, poor stand, wilting, nutrient deficiency, and lodging. Roots may appear abbreviated or "stubby" looking. However, all these symptoms can be caused by other factors, so the only way to verify if P. minoris a problem is to have a nematode assay conducted by a credible nematode diagnostic lab.
Paratrichodorus minor is known to occur deeper in the soil than many other plant-parasitic nematodes. In experiments, a large percentage of P. minor populations occurred between 8 to 16 inches deep, below the typical treatment zone of soil fumigants. This allows many P. minor to escape being killed by fumigant treatments. Population numbers of P. minor are known to rebound following soil fumigation to numbers higher than if no treatment were used. Therefore, soil fumigants, while effective treatments for other plant-parasitic nematodes, often are not recommended for management of P. minor.
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Stubby-root nematodes use their onchiostyle like a dagger to puncture holes in plant cells. The stubby root nematode then secretes from its mouth (stoma) salivary material into the punctured cell. The salivary material hardens into a feeding tube which functions as a "straw" enabling the nematode to withdraw and ingest the cell contents through the tube. After feeding on an individual cell, the stubby-root nematode will move on to feed on other cells, leaving old feeding tubes behind and forming new ones in each cell that it feeds from.
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