Biological control is becoming the most sensible as well as most economical way to prevent insect crop damage. In many cases, one insect is used to control another. Nematodes are utilized this way by commercial growers and to a lesser extent by home gardeners.

Nematodes are tiny, thread-like organisms. They are so slender that they are usually unseen. Sometimes, if you have a clean glass dish garden or terrarium, they can be seen between the glass and the potting soil acting like very thin, very fast earthworms. (They looked so unpleasant to me that I threw out our entire nematode infested terrarium.)

The parasitic nematodes live within the body of certain aphids, borers, carpenter worms, weevils, various larvae, maggots, grubs, earwigs, cutworms, etc. They bring with them into the insect host's body a deadly bacteria which multiplies and is the food for the nematodes.

Dehydrated nematodes are purchased as a powder or in a dry sponge. After water is added they may be distributed in several ways. The nematode solution can be sprayed or sprinkled on the crops. They may also be dispersed through a trickle irrigation system, injected into plant stems with a syringe, squirted into borer holes, or soaked into absorbent tree bands.

Some nematode, though, are pests themselves. These cause damage to plant root systems (as did those that were in my glass terrarium). These "root-knot nematodes' can be controlled by drenching the soil with a poison extract from the chinaberry tree or the Indian neem tree. They can be "solarized" or "cooked" by heating the soil with a clear plastic cover. Marigolds discourage nematodes from feeding (give them indigestion?) and stop them from reproducing. Nematode destroying fungi can be encouraged in the garden by incorporation organic matter into the garden soil. Also, a three year crop rotation with plants that are not susceptible to nematode damage may reduce a destructive nematode population.