Farmers now have a fragrant method of controlling nematodes in their crops.
Vegetable growers are familiar with the nematode and the damaged yields that worm infestations can cause. Marigolds have a natural but not well understood ability to eliminate nematodes.
The theory has been a long-held folk remedy for gardeners facing a variety of pests. Nematodes are found mainly in sandy soils around the world.
Fumigation is often the only way to remove the pests, but it is expensive at more than $400 per acre, and it kills more than just the offending worms.
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Even at seed prices of $312 per kilogram for the common Cracker Jack marigold, the cost is comparable to fumigants and will likely last longer than the one season’s control provided by fumigation.
“You are killing all sorts of microscopic life when you fumigate, some of it beneficial,” said Bruce Reynolds, of Agriculture Canada’s research centre in Delhi, Ont.
Reynolds said the cost of marigold seed will probably drop drastically as the plant comes into commercial seed production during the next few years.
In sandy soils green manure crops are often grown to build up depleted nutrients. Marigolds produce as much plant product as rye crops that are normally produced for this rotation. But the rye crops can be hurt by the worms, while marigolds drive the worms away.
In addition to providing green manure and nematode protection, the mari-golds require no nitrogen or other fertilizer and have few natural enemies.
A new variety of marigold, Petula, is now being tested in Ontario. Growing more than two metres high, the plant is expected to provide better green manure with lower plant populations.
Nematode populations can damage cereal, fruit and vegetable crops and can go undetected in average to high moisture years. When drought occurs, the worms’ effect on plants becomes evident as they feed on the roots.
“We expect that orchard and row crop growers could plant the mari-gold even between the crops. Weed control and ground cover is needed in orchards anyway and this may be an answer,” said Reynolds.
