nematodes

This year we continued our tomato trails. After last year's problems with nematodes we decided to test control methods for these pests. We grew and rated heirloom tomatoes in one plot at McClellan Ranch in 1992. In 1993 the City of Cupertino offered us a larger plot so we moved our project and re-grew the most favored varieties. The fruit yields seemed to be lower than in prior years. When we removed the plants at the end of the season we discovered galls on the roots. Dr. Kolodge diagnosed root-knot nematode damage. Based on this information we decided to experiment with different methods of control. Prior to planting tomatoes in 1994 we took samples of the soil and sent them to the nematology department at U.C. Davis for a baseline pest count.

U.C. Publication 4083 (Radewald, J. D. 1978. Nematode Diseases of Food and Fiber Crops of the Southwestern United States. Univ. Calif. Press.), "nematode diseases," explains that nematodes are members of the roundworm family. This is a very large family and many species are plant parasites. Although several different species are present in most soils they are plant-specific. The species we are concerned with is classified Meloidogyne, a sedentary endoparisite. The common name is root-knot nematode. Their life-cycle is characterized by burrowing into the roots of host plants for food and to deposit eggs. As the eggs grow, a visible gall is produced on the root, hence the name root-knot. This galling interferes with plant growth. After hatching, the nematodes migrate away from the roots from only a few inches to a foot during a season. They spread to wider areas chiefly by human intervention, through the use of hand tools or farm machinery. It is important to disinfect any tools that are used where nematodes are present to avoid spreading them to unaffected areas

by: Allen Buchinski

Introduction

Nematodes are tiny, round-bodied, unsegmented, worms. Most yards typically have billions of them in the soil, feeding on organic matter, bacteria, insects and plants. Nematodes are one of the most common of all animals, but because they usually can't be seen without a microscope, they aren't very well understood outside the scientific community of nematologists. Approximately 10% of all nematodes feed on plants, living around or in the roots. The most well known is the root knot nematode (Meloidogyne spp.), because of the distinctive galls it causes on infected roots, it's wide distribution, and the wide range of plants that it attacks (including most common vegetables, ornamentals, and fruit trees.)

by: Allen Buchinski

In my previous article, I discussed "what are nematodes" with a focus on plant parasitic types. Here we'll focus on the beneficial kind.

As you surely remember, nematodes are tiny round worms that proliferate in nature. Of all nematodes, only a portion cause problems in your garden, these types live on or in plant tissue, disrupting the plant's natural processes. There are many other nematodes that feed on other things, including organic matter in the soil, bacteria, insects, even animals. It's the insect eating variety that's of interest to us here, harnessing them to help us with insect pests in the garden.

How Do They Work?

Since nematodes live in the soil, they can be used against insects that spend at least part of their lifecycle underground, typically the larvae form (although researchers are also exploring the methods for applying nematodes above ground as well by timing the release in such a way that they can enter a host insect before succumbing to the elements.) There are two strategies used by nematodes for finding prey, depending on the species: