Gardening Articles: Care :: Pests & Problems
by Dan Hickey
Apply beneficial nematodes to your lawn or garden with a watering can or pump sprayer.
When it comes to nematodes, it's the destructive ones that get all the press. And they deserve it--plant parasitic nematodes cause an estimated $78 billion in damage to crops worldwide.
It's only been recently that beneficial nematodes have stolen the spotlight. After decades of trying, researchers now know how to efficiently mass-produce these insect-parasitic nematodes for use in the farming industry, and that's good news for gardeners. These tiny critters help control many common garden pests, including armyworms, rootworms, fleas, fungus gnats, stem borers, root weevils, cutworms, and billbugs. In field research, they've been shown to be just as effective as traditional insecticides on these pests.
Today, there are dozens of American companies selling beneficial nematodes to farmers and home gardeners. The worms can be used as a pest control for lawns and golf courses, gardens and greenhouses.
Nematodes for Gardeners
For gardeners, beneficial nematodes are attractive as biological pesticides because of their effectiveness and environmental safety. They contain no toxins and are harmless to humans and all other warm-blooded animals. They won't harm fish or plants and are ideal for insect-infested areas around drinking wells or other environmentally sensitive locations that preclude the use of chemical pesticides. As a testament to their safety, the U.S. Environmental Protection Agency waived registration requirements for beneficial nematodes.
"We see a lot of gardeners using beneficial nematodes on white grubs," says Jim Cate, president of Integrated Biocontrol Systems in Lawrenceburg, Indiana. "They're good on a number of beetles that live in the soil. For example, carrot weevil, asparagus weevil, black vine weevil."
However, effective use of beneficial nematodes requires knowledge of the nematodes and the insect you want to control. Simply applying them like a traditional pesticide won't work.
What is a Nematode?
In an average backyard, there are billions of naturally occurring nematodes (also known as roundworms) in the soil. They are 0.6 to 2 millimeters long and often hardly visible. Some feed on plants, some feed on animals, some feed on decaying organic material or bacteria, and some (the beneficial nematodes) feed on insects.
Beneficial nematodes belong to one of two genera: Steinernema and Heterorhabditis. Four species of Steinernema and one species of Heterorhabditis are commercially available in the United States. Steinernema is the most widely studied beneficial nematode because it is easy to produce. Heterorhabditis is more difficult to produce but can be more effective against certain insects, such as the white grubs of Japanese beetle.
"There are hundreds of nematode species parasitic on insects, but only a few that show commercial potential. Currently, only five species are produced commerically in the U.S.," says Harry Kaya, professor of nematology at the University of California-Davis. "We expect to see more beneficial nematodes available in the future because some nematodes are more effective on certain insect pests."