Root-knot nematodes are common visitors to East Texas fields of pumpkins and many other vegetables, but their presence is anything but a holiday treat for growers, according to a Texas AgriLife Extension Service expert.

“Root-knot nematodes are the biggest problem many of our East Texas vegetable growers have to face,” said Dr. Karl Steddom, AgriLife Extension plant pathologist.

Steddom recently completed trials comparing various fumigants and biological controls for root knot nematodes on pumpkins.

“The pleasant surprise is that one of the biological controls was one of the most effective,” Steddom said.

And he said the results should be applicable to all the crops affected by the pest. The list is considerable. Root-knot nematodes can knock back yields and quality on pumpkins, tomatoes, sweet potatoes, beets, cucumbers, carrots, peaches, watermelons, and okra. Even ornamental plants such as roses that have been started from rootstock can be hammered by the pest.

“Some watermelon varieties are marginally affected, but they can flat-out kill some crops like okra,” Steddom said.

Root-knot nematodes are tiny parasitic worms that infect plant roots. They form galls or knots on the plant roots that block the flow of nutrients and photosynthesis products. The pest is found worldwide but thrives in the sandy soils common to East Texas, he said.

“One of the biggest problems with these (pests) is that their eggs can lay dormant in the soil for years,” he said. “They’re very difficult to get rid of, and once a grower gets nematodes in a field it can be a big issue for production for years to come.”