Weed Control TestingBy George Grow
This is Bill White with the VOA Special English AGRICULTURE REPORT.
Weeds are a problem for many farmers. Weeds invade cropland or other areas where people do not want them to grow. Many weeds can destroy more desirable plants. They compete with them for sunlight, water and minerals in the soil.
The United States Agricultural Research Service has a center for plants from other countries that Americans consider to be weeds. The plants are kept in five greenhouses in Frederick, Maryland. Each building is part of a restricted area. Scientists infect the weeds with bacteria and other organisms that cause disease.
The bacteria and other organisms also come from other countries. They also are kept in a restricted environment. The scientists test the safety of the organisms and their effectiveness in controlling the weeds. The program is part of a national campaign to reunite foreign weeds with their natural enemies. Scientists are trying to control the weeds with biological methods instead of using chemicals.
Plants from other areas usually have few natural enemies in the United States. In some areas, foreign plants have displaced native plants. Some invaders, like yellow starthistle, have spread rapidly. Starthistle is just one of up to five-thousand foreign plants that have become established in the United States. Yellow starthistle is an extremely strong plant. People must spray chemicals for several years to control the spread of the weed. This can increase the possibility that the chemicals will spread through the environment.
The scientists in Frederick work with groups in the United States, Britain, China, Croatia, Hungary and Switzerland. The groups provide bacteria and other organisms for the weed control testing program.
The scientists identify the organisms and put them in a storage area. Then they collect reproductive materials from the organisms and spray them on weeds growing in the greenhouses. Signs of disease appear on the plants in two to three weeks.
The scientists share the results of such studies with agricultural officials and other groups. Another agency of the Agriculture Department makes the final decision about permitting the release of foreign organisms in the wild.
This VOA Special English AGRICULTURE REPORT was written by George Grow. This is Bill White.