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Trap Cropping for Management of Root-knot Nematode by Home Gardeners

The Issue

Plant-parasitic nematodes are microscopic roundworms that cause problems for home gardeners. Few control measures are available to California homeowners other than keeping the planting area fallow for two years, or planting nematode-resistant tomatoes.

The root-knot nematode, Meloidogyne sp., causes the most serious problem and its effects are readily visible to home gardeners by the presence of knots or galls visible on roots.

What Has ANR Done?

Trap cropping is a nematode management technique that has been tested periodically since the late 1800s. A susceptible plant host is planted and larvae of a sedentary parasitic nematode such as root-knot are induced to enter and establish a feeding site on the plant. Once this has occurred, and the female nematode begins to mature, she is unable to leave the plant root. The plants are then destroyed before the life cycle of the nematode can be completed, trapping nematodes within the root.

By itself, trap cropping is not likely to provide the same level of control as a chemical nematicide, because not all nematodes are induced to enter the roots. Because of this, it has not been widely used in commercial agriculture where nematicides are available to control nematodes.

Field trials conducted by UC Davis researchers have demonstrated that trap cropping, while not providing total nematode control, could be a viable technique for home gardeners.

The Payoff

Nonchemical Control of Nematodes for Home Gardeners

A trap crop can be any root-knot nematode susceptible seed easily available to home gardeners. Examples of trap crops are carrots, tomatoes, and beans. The trap crop is planted, and upon germination, nematodes enter the roots. Two weeks after planting, the crop is destroyed by tillage, such as hoeing, to destroy the root system and the nematodes trapped within.

Trap cropping should provide a degree of nematode relief to home gardeners for root-knot sensitive crops such as carrots, heirloom varieties of tomatoes, beans, potatoes, sweet potatoes, cucumbers, peppers, squash, and melons.

A potential problem with trap cropping is that something prevents destruction of the crop until so late in the nematode life cycle that reproduction occurs and the nematode population increases. If something should prevent timely crop termination, the use of common vegetable crops for the trap crop will make it so that home gardeners are no worse off than they would have been, and can continue to let the crop mature to harvest.


Supporting Unit:

Department of Nematolgy, UC Davis and Slosson Endowment for Ornamental Horticulture
Becky B. Westerdahl
Department of Nematology
UC Davis