Nematodes and other garden problems

Modern vegetable production uses fumigants to clean the soil from many soil diseases, nematodes, and some weeds.  Fumigants are often quite toxic and often applied as a gas into the soil.  The soil may be covered with plastic to hold the fumigant in the soil to better kill the pathogens.  After a period of time the fumigant either dissipates and/or decomposes.  Then the plant is either seeded or transplanted into the soil, often through holes punched into the plastic.  The results are improved plant growth with less disease and often free of damaging nematodes.

Forked carrots caused by nematodes

Nematodes are minute round worms that live in the soil and often infect plant roots causing slow plant growth, forked carrots and other maladies.  They are so small they are usually not visible to people and there are numerous species.  Some common nematodes are cyst, root knot, lesion, dagger, and sting nematodes.  There are a few foliar nematodes and others cause medical problems in humans and other animals.

So, what can you do?  Most home gardeners do nothing and accept the damage.  There is a solution that will give your garden a great advantage.  Members of the brassica family such as mustard, turnip, and radish plants produce natural chemicals that can control or at least limit the damage from nematodes and plant diseases.  The diseases that may be controlled are verticillium, pythium, fusarium, rhizoctonia aphanomyces, and fusarium. 

Mustard plants in flowers

These plants are cool season annuals that can be planted in the fall as a cover crop or in very early spring.  When the mustard plants are chopped up and tilled into the soil, they decompose.  The decomposition releases glucosinolates which act as a biofumigant.  The plants, especially the mustard should be chopped and tilled before or at flowering time so the seeds don’t mature.  Mustard plants can be a weed that easily gets out of control.  Using these plants as a natural fumigant will not inhibit the growth of vegetables and the food grown will be perfectly safe to eat.

Tillage radishes

Turnips and tillage radishes can be planted in the fall and grow very well before freeze up.  (Don’t use the small round radishes)  The long cylindrical radishes grow quickly and produce a taproot that will grow deep into the soil improving the soil characteristics.  The deep root when decomposed creates channels that help handle soil water.  Turnips will grow similar to tillage radishes but don’t grow as deep.  When the turnips and radishes are tilled they also release chemicals that help control nematodes.  Tillage radishes and turnips can be seeded in the fall and generally will grow enough to be effective in improving next year’s garden.  Do remember to chop well and till into the soil.  If you choose to grow them as a cover crop, they do provide animal food and are grazed.  You, also, can eat them if you desire.

The Garden Doc