Ask the Master Gardeners: December 2010
Guadalupe County Master Gardeners is responsible for this content, which is not edited by the Wilson County News or wilsoncountynews.com.
Q: I just pulled up my tomato plants because a freeze was coming and they weren’t doing well anyway. The roots were covered with knots. What can be done about root knot nematodes?
A: Root knot nematodes can be identified by the swollen roots with galls. These nematodes are small worm-like animals that live in the soil and feed on the roots. Another hint that you might have root knot nematodes is that the infected plants are stunted, yellow, not vigorous, and look like they are declining. Aggie-horticulture, in their section on tomato root disorders, says that the root knot nematode is very difficult to control, but does give several suggestions. (The overall website is aggie-horticulture.tamu.edu.)
First, use crop rotation with a non-susceptible species. This means that you should not plant tomatoes in the same spot year after year (or in the same spot as cotton or okra). Secondly, make sure you buy tomato varieties that are resistant. In the nursery, look at the tag and make sure you are getting tomatoes that have an N on the label.
The Earth Kind section of Aggie-horticulture suggests that if you have a large garden area infected with root knot nematodes, plant Elbon rye (cereal rye) in the fall. This fast growing, cold tolerant, annual grass actually is a trap crop for nematodes. Once the nematodes enter the cereal rye roots, they can’t escape and are doomed. Apply three-fourth to one pound of seed per one hundred square feet of garden. Shred and till the Elbon grass into your garden one month before planting the spring garden. This will give the grass time to decompose. (Don’t let the cereal rye form seed heads. You don’t want the seeds to sprout in your garden.)
Malcolm Beck and Howard Garrett list several other ways to control nematodes in their books “Texas Organic Vegetable Gardening” and “Texas Bug Book, The Good the Bad and the Ugly.” Beck and Garrett suggest increasing the organic level in the soil by using organic fertilizers and by applying products to increase the soil’s microbial activity. They say that citrus pulp or liquid will completely control root knot nematodes. I probably am not going to grind up citrus peelings, but I think I will try another of their suggestions which is using cedar flakes or chips as a one-inch mulch around my tomato plants. One of his reasons as to why this helps control nematodes is that there are several fungi that attack nematodes. These beneficial fungi need a fertile, aerated, balanced soil with a supply of carbon to use as energy. Hence the cedar flakes. I like to use cedar as mulch anyway because it smells good, and I think the strong odor deters insects.
Clara Mae Marcotte is a Texas Master Gardener with the Texas AgriLife Extension. If you have a question to be answered, call the Master Gardeners at 830-379-1972 or leave a message to be answered. The website is guadalupecountymastergardeners.org. The Master Gardener research library is open Mondays from 8:30 to noon, on the second floor of the Texas AgriLife Extension building, 210 East Live Oak in Seguin.