Nematodes part three

For the past couple of weeks we have been discussing nematodes and how to discourage them in our gardens. Today we will explore some additional approaches to nematode control. 

So far, we have agreed that garden site selection, rotation of crops, sanitation, the use of resistant varieties, fallowing, and soil solarization are important ways to minimize nematode populations. But wait-there are still other strategies to be considered.

One such strategy, and the most basic one, is keeping your plants free from stress. The less stress plants experience, the more they are able to resist the attacks of nematodes. Watering plants deeply and less often will stimulate the development of a deep root system which serves to reduce drought stress on plants. Proper management of diseases and insects also reduces stress as will proper attention to plants’ nutrients needs.

Another method is the addition of organic matter to the soil. Besides just being an excellent tool to improve soil structure and fertility, organic matter helps produce healthier plants and will improve any soil, whether sand or clay. Pine bark, if fresh and ground up into small pieces, has been reported to aid in the suppression of root-knot nematodes. This should be done a month or two before planting.

Yet another nematode-suppressing tool is the planting of suppressive crops. Such crops suppress nematodes naturally. There are several plants which minimize nematode damage in vegetable crops. These plants produce organic compounds which are toxic to nematodes and are released from the roots of plants either while living alongside the vegetable crop or incorporated into the soil as a green manure. Other plants act as trap crops, preventing the nematodes from maturing once they enter their roots. Some nematode suppressive crops are certain varieties of French marigolds and chrysanthemums, castorbeans, partridge peas, crotalarias, velvetbeans, rapeseed, common vetch, and various grain crops.

Growing a nematode suppressive crop will not eliminate nematodes from the soil. However, it may allow for the production of a successful crop by reducing or diverting the nematode population. The use of suppressive crops has been shown to be at least, if not more, effective than fallowing.

One last method of nematode control is the use of organic products. Two such products are DiTera and Clandosan 618.

Clandosan 618 is a nematicide made up of chitin extracted from shellfish by-products, soybean meal, and urea. Chitin is a major component of the body wall of nematodes. Clandosan works by increasing the population of microbes which feed on chitin. This approach has been shown to reduce the number of nematodes for as long as it takes to produce two typical crops. Control, however, is said to be sporadic and requires large quantities of the product. If used, Clandosan should be tilled into the soil about two weeks before planting.

Ditera provides protection against nematodes that damage grape, fruit, nut, and vegetable crops. Its chemistry is based on the fermentation of a naturally occurring microorganism (Myrothecium spp.) and is applied in granular or liquid form.

I trust these articles on nematode control have given you some ammunition against the dreaded root-knot nematode. Good luck! You will need it!

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.