Plant Pathology Infobytes

January 27, 1998
Root-Knot Nematodes: Your Landscape Plants Could Be Victims

The only crops affected by root-knot nematodes are vegetables, right? Think again -- these pesky microscopic critters also attack a wide range of woody landscape plants. So if your azaleas, gardenias, boxwoods, camellias, Japanese hollies, or other ornamental plants have declined over the past few years, root-knot or other type parasitic nematodes could be the reason for their poor growth.

Landscape plants affected by root-knot nematodes are likely to be stunted and often show symptoms of nutrient deficiency. During the growing season, wilting may occur even though soil moisture is adequate.

The reason for plant stunting and wilting isn't hard to understand since a severe infestation of root-knot nematodes can convert the root system into a mass of short, thick, bumpy roots incapable of absorbing water and fertilizer nutrients. Since root-knot affected roots are so unhealthy, they often are invaded by root rot fungi and bacteria which cause affected plants to further decline.

Homeowners should suspect root-knot nematode problems on landscape plants which still remained unthrifty this past season despite adequate water and fertilization. The root swellings can easily be observed by gently lifting the root system of unthrifty plants from the soil.

The usual remedy for root-knot affected plants is removal and destruction of both plants and soil and replacement with clean, nematode-free soil and a healthy plant. Nematicides (chemicals applied to the soil to control nematodes) are generally no longer available for use by homeowners, but some nematicide products are still available at garden supply stores. When applied according to label directions, they may help control root-knot nematodes.

Also, when you install a replacement plant, take a good look at the root system to make sure it's free from symptoms of root-knot nematodes. Garden centers handle high quality planting material, but infected plants occasionally slip by so it's a good idea to examine the roots before planting.

Homeowners who wish to verify the presence of a root-knot nematode infestation may also do so by collecting a early spring soil sample from around the roots of plants. The sample may then be analyzed for root-knot and other nematode pests free-of-charge at the Mississippi State University Plant Pathology Laboratory. Check with the County Extension Office for sample collection instructions and additional information on how to manage pest problems in the home landscape.


Written by the late Dr. Frank Killebrew

A black line that separates the body text from footer information