Science Video

Natural Pest Control
Research Entomologist Prescribes New Form Of Pest Control

July 1, 2007 — An Ohio State University entomologist affiliated with the Ohio Agricultural Research and Development Center has recommended a new, innovative and chemical free variety of pest control, in the form of nematodes. The microscopic pest-killing nematodes aim to execute the same functions as traditional chemical pesticides, but minus the potential hazardous pollution. According to the scientist, nematodes also promise to be animal, human, and environmentally friendly.

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Fruits and veggies are good for us, but the chemical pesticides they're sprayed with are not. Now, scientists are looking at ways to use the food chain to naturally battle bugs.

Nematodes are microscopic roundworms that live in the soil and are waging war on pests. Parwinder Grewal, Ph.D., a nematologist from The Ohio State University, is studying how to use them. "Among the biocontrol agents, nematodes are the most intensely researched nematodes because potential is seen," Dr. Grewal says.

The nematode first tracks down an insect, invades its body, releases bacteria, and it is dead within 48 hours. The nematode eats the bacteria and insect to mature into an adult to reproduce hundreds of thousands of nematodes looking for a new bug. "So their life cycle continues by finding newer insects," Dr. Grewal says.

The are advantages of using nematodes over chemical sprayers. First, they're already part of the ecosystem and are natural -- and they don't pose harm to people and wildlife. So, it's cheaper in the long term. "We cannot keep producing chemical pesticides," Dr. Grewal says. Nematodes can be used with standard sprayers, and could even be shipped to you at home -- collected in a sponge. The main limitation is shelf life. Right now, nematodes only last about five months but scientists are working to get that to a year. Dr. Grewal says nematodes could take care of about 60 percent of soil pests. They're now looking to isolate certain genes to make them even more effective.

BACKGROUND: Biocontrol agents are becoming more popular as both the public and regulators recognize the environmental and human health risks associated with chemical pesticides. One type of biocontrol agent is nematodes, which have proven to be highly effective against a wide variety of plant, animal and human pests.

WHAT ARE THEY? Pest-killing nematodes are tiny roundworms that can be applied through sprayers or irrigation systems to do the same job as chemical pesticides -- minus the potential pollution. Unlike parasitic nematodes, which cause disease in plants, animals and humans, beneficial nematodes are used to fight costly insect and slug pests in vegetables, turf grass, citrus, strawberry, cranberry and ornamental crops. They have also shown promise against fleas, ticks and lice. For instance, citrus growers in Florida rely on the microscopic worms to combat the root-feeding citrus weevil.

Nematodes eat grubs and rid lawns and groves of other common insect pests, such as black vine weevils, beetles, leas, and cutworm, by releasing a bacterium that kills the pest. Nematodes are best applied when soil conditions are wet -- right after it rains, for instance -- with a soil temperature of at least 60 degrees F. They should be applied late in the day, or when it is cool and overcast, since exposure to ultraviolet light will kill them. Nematodes are non-toxic, and start becoming effective within 72 hours of being released into the soil.

THE ABCS OF NEMATODES: There are more than 15,000 known species of nematodes, and a single handful of garden soil may contain thousands of the creatures. They can lay more than 200,000 eggs in a single day. The nematode has an unusual skin that secretes a thick outer shell -- called a cuticle -- that is tough yet flexible, and is shed four times in the nematode's lifetime before it reaches adulthood. The head has a few tiny sense organs, and a mouth so food can be pulled into the throat and crushed. Because they have no discrete circulatory or respiratory system, they are vulnerable to environmental conditions. Many nematodes can exist in a state of suspended animation (called cryptobiosis) in order to survive extreme conditions, such as dryness, heat or cold, returning to life when the environment becomes more favorable.

Note: This story and accompanying video were originally produced for the American Institute of Physics series Discoveries and Breakthroughs in Science by Ivanhoe Broadcast News and are protected by copyright law. All rights reserved.