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.”