Nematodes – part one

Most gardeners are familiar with the problems caused by the most common and unwelcomed insects and diseases that frequent their crops. One such intruder is the nematode. Few gardeners, however, are aware of the true nature of nematodes and the damage that they can cause. I have written on this topic before, but given that it is such a prevalent problem in many gardens, I have chosen to write on it again. 

Nematodes are microscopic, wormlike creatures which inhabit the soil and feed on the roots of plants, impairing their ability to take up water and nutrients. Symptoms of this damage include stunting, yellowing of plant leaves, and loss of plant vitality. Although rarely killing plants, nematodes can drastically reduce plant growth and yields. Nematodes are usually found in certain areas of the garden and spread by movement of infested soil through cultivation, on soil clinging to garden tools and equipment, or on the roots of transplants introduced into the garden. 

There are many kinds of nematodes found in the South, but the most common and destructive is the root-knot nematode. Root-knot nematodes attack the roots of plants causing distinct knots, swellings, or galls on them. This article is devoted to the root-knot nematode. 

Nematode control is not easy. It requires long-term planning and no currently known control practice will permanently rid nematodes from the garden or orchard. Nevertheless, nematodes can be effectively managed by the use of one or more of the following practices.

First, consider that nematodes are most prevalent in sandy or sandy loam soils. If you have these soil types in your garden, be aware of the potential for nematode infestations. 

With this in mind, know that site selection and rotation can be important considerations in the fight against nematodes. Have your garden soil tested for the presence of nematodes. Collect soil in the fall when nematode populations are highest. Avoid sampling in the winter or early spring since nematode numbers are lowest during these times and may not be detected. Take samples in several areas of the garden from the top 8 to 10 inches of soil. Submit to your local Cooperative Extension Service office for analysis.

Another strategy for nematode control is sanitation. Nematode infected plants (especially roots) should be removed from the garden and destroyed after harvest. Till the garden immediately afterwards to bring any remaining plant roots to the surface. Do this several times during the winter. The drying effect of the wind and sun will destroy nematodes and their eggs, whereas vegetable roots left in the soil through the winter will serve to increase their population the following year.

Crop rotation is another nematode control method. A particular vegetable belonging to the same family should not be grown in the same location more than once every three years. 

If possible, also rotate garden sites. If not, then rotate related crops in one family group with crops in an unrelated family group within the garden.

Next-more on nematode control.

Tim Lewis is a Georgia Green Industry Association Certified Plant Professional, gardening writer, former Perry High School horticulture instructor, and former horticulturalist at Henderson Village and Houston Springs. He and his wife, Susan, own and operate Lewis Farms Nursery located on Hwy 26 two miles east of Elko, where he was born and raised. He can be reached at (478)954-1507 or timlewis1@windstream.net.