Posted 19 November 2007. PMN Crop News.
Root Knot Nematodes Appear in Central Missouri
University of Missouri. cafnr.missouri.edu
Columbia, Missouri (October 18, 2007)--If your home garden didn't do so well this year, it could be due to root knot nematodes.
Root knot nematodes are microscopic worms that can infect vegetable roots causing serious symptoms, producing galls or knots on the roots, said Bob Heinz, coordinator of University of Missouri Extension Nematology Lab.
While not common in Missouri, these nematodes are beginning to appear due to warm winters, he said.
"Traditionally, they have said that the southern root knot nematode doesn't go north of Interstate 70," Heinz said. "We are sort of on a line. In all the years I have worked in Columbia we have never had root knot nematode."
Heinz recently found the nematode in six of nine of Columbia's community gardens.
The nematode can travel only by soil or plant material. In a community garden, 10 to 20 people use the same compost piles and walk across each other's plots, he said.
"It is so easily spread. A teaspoon of soil can have thousands of nematodes. You can carry them on your shoes or vehicle tires or by borrowing or lending garden tools or a tiller," he said.
Chemical control of nematodes in home gardens is not recommended, said Heinz.
Good garden hygiene is important. Clean your garden tools with a 10 percent bleach solution and power wash the tiller. Pull infested plants to remove as much root as possible.
Above-ground symptoms include plants showing less vigor, slower growth, yellowing wilt during summer heat and stunted or smaller fruit. The only way to be sure if your garden has root knot nematodes is to pull up and examine the roots during fall cleanup. Galls may be small or up to an inch in diameter.
Root knot nematodes overwinter as egg masses in the soil or on the roots. A good week or two of zero degree weather with no snow or other insulatating material such as plant debris can freeze the soil deep enough to eliminate the pest. Clear away grass or garden debris to allow cold temperatures to penetrate the soil.
Keeping part of the garden fallow reduces the number of root knot nematodes because they will not have a host on which to feed.
There are many varieties of nematode-resistant tomatoes, but not many choices with other vegetables.
Soil solarization can control the pest. Soil temperatures reaching 125 degrees for 30 minutes will kill nematodes. The garden section to be treated should first be tilled and moistened well before being covered with clear plastic for the months of June through August.
Sometimes it is easier to just start a fresh garden spot, Heinz said.
Root knot nematode infestation can be confirmed by sending a soil sample to the Extension Nematology Lab, Rm. 23, Mumford Hall, Columbia, Mo. 65211. There is a $20 fee for the test. For more information, go to soilplantlab.missouri.edu.