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The Search For Biological Controls Of Weeds
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# : |
10753 |
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Section : |
NATURAL SCIENCE
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| Issue
Date : |
6 / 1993 |
2,438 Words |
| Author
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Heather B. Hayes
Heather B. Hayes is a freelance writer living in the
Washington, D.C., area. |
It is a fact of nature that to maintain an ecosystem's proper equilibrium, each organism--animal or plant--must be checked and balanced by a natural enemy. To alter the balance concerning even one organism is to change the natural order of the ecosystem. And many regions in the world must deal with the effects of this altered balance.
Consider the United States, for example. When European immigrants came to American farmlands, they brought with them their best varieties of grains and cereals. Unknowingly, the settlers also carried along weed seeds--but not the weeds' natural enemies like fungi, bacteria, and insects that had helped keep them under control in Europe. As a result, the weeds were able to grow and reproduce unchecked, taking over whole areas in their new habitat.
One hundred years later, weeds such as leafy spurge and yellow starthistle cost American farmers and livestock owners billions of dollars annually in lost crops and pastureland. Even under the onslaught of continuous chemical treatment, the weeds grow quicker, more aggressively, and stronger then endemic plants, which must also contend with their own natural enemies. As a result, more desirable plants are easily displaced. Currently, millions of acres of weeds exist in the United States.
After years of listening to complaints from farmers and ranchers, the U.S. Department of Agriculture (USDA) in the 1970s resolved to find, test, and release the natural enemies of the troublesome weeds. In 1989, USDA officials sent Agricultural Research Service scientist Rick Bennett, one of the country's most promising young plant pathologists, to Eastern Europe, believed to be the area of origin for leafy spurge, to locate and bring back bacterial and fungi that would defuse the weed.
Economically, leafy spurge is one of the most devastating weeds in the United States. Found predominantly in the northwestern Plains states, it displaces pasture plants and crops like alfalfa, has no forage value, is poisonous to cattle, and, with a large and elaborate root system, is basically not affected by herbicides.
Bennett's goal was to find as many pathogens (enemies) in Eastern Europe as possible. While in the area, he would also spend time in Mediterranean countries like Greece and Italy looking for pathogens that would infect yellow starthistle, a thorny, toxic weed that has overwhelmed many agricultural areas in the western United States and British Columbia.
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