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 that 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 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 their production for years to come.”

The infestation may start out in a small area of a field and at first may not be at high enough levels to cause significant losses in crop yield or quality, Steddom said. But if the field is left untreated, it’s almost a sure bet that the nematode population will grow and spread throughout, he said.

Steddom began the study because there wasn’t a lot of field data on two of the label products. He could have tested the products on a number of different crops, but he chose pumpkins because they’re less labor intensive to harvest, he said.

He tested nine different combinations of products on a site at the Texas AgriLife Research and Extension Center at Overton.

He conducted the tests in a field with a field that had a sandy loam soil and a high population density of root-knot nematodes.