After all Georgia cotton farmers have dealt with this year, another pest is rearing its tiny head.

Nematodes -- worms that live on or near plant roots in the soil - - present much more of a problem than many experts thought.

"Nematodes don't just pop up overnight," said Rich Baird, a plant pathologist with the University of Georgia Extension Service. "They build up slowly but surely. Plants can look OK but still be sustaining yield losses."

Nematodes steal water and nutrients from plants. Baird said growers describe infested fields as "tired" or worn out, but the plants don't show obvious disease or insect symptoms.

Farmers may water or fertilize the crop and expect yields and the plants' health to improve, but if nematodes are present, that may not happen. Yields may actually begin to decline.

Drought periods intensify symptoms, as the root-dwelling worms take more water and nutrients.

Nematode populations have followed the marked increase of Georgia cotton acreage over the past three years.

"As more first-time growers produce cotton, they may not know the basics of nematode detection and control," Baird said.

The three most common nematode species -- root-knot, lance and reniform -- can severely damage almost any cotton variety in just one year.

Rotating other crops with cotton can reduce populations, but Baird said some nematode species can infect many plants, including corn, soybeans, wheat, rye, vegetables, alfalfa and common weeds.

Some cotton varieties are more resistant to certain nematode species. But if farmers plant cotton in the same field year after year, Baird said the problem can build to the point that nematodes may claim more than half of the grower's crop.

Nematodes travel from field to field in soil carried by equipment. Baird tells farmers to clean loose soil from equipment before moving to another field, or to work in clean fields first, then move into infested ones.

"Growers can spread nematodes from one field to the next unless they're aware of the problem," he said. A timely soil sample can tell farmers if nematodes are in their fields.

Baird suggests taking samples just before or just after harvest, within six inches of the plant roots and about six inches deep.

"You can divide the sample in two and send one off for soil nutrient analysis and the other for nematode analysis from the University of Georgia," he said.

The lab in Athens sends the results back to the county agent, who helps growers make sound management decisions based on nutrient analysis and nematode test results.

If testing reveals nematodes, growers must do several things to control them.

"First, he's going to have to use effective crop rotations," Baird said.

Planting a nonhost crop in an infected field for two to three years can reduce nematode populations to acceptable levels. Which crop to plant depends on the nematode species in the soil.

Baird said planting nematode-resistant or cover crops helps reduce populations, too. Farmers may be forced to use expensive, but effective, chemical nematicides as a last resort to control the destructive nematodes.

An ongoing survey of Georgia farms continues to show nematodes to be more of a problem than anyone thought. This survey should help county agents know the nematode situation in their county and how to deal with it.

"We want to help before it does become a problem in fields by answering the question 'What do you have in your field?'" Baird said. "Once they're in a field, they never go away, so this can be a long-term problem that requires long-term management solutions."