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In the 1950s, the American public became aware that certain chemicals endanger human health and the environment. In response to this threat, new rules and regulations regarding chemical manufacture, use, and disposal were developed under state and federal law. Today, the public has a much better understanding of the chemical pollution problem and generally supports management efforts. The 1990s have brought us face to face with another serious environmental threat: The invasion of the American landscape by aggressive nonnative plants. While farmers have always fought a battle with weeds in crops, invasion of these and other formerly weed-free lands has increased exponentially in recent decades. Because they often look no different than native plants and animals, nonnative plants can become established and cause serious economic and ecological damage before they are detected. Since the 1960s, the United States has made dramatic strides in most areas of environmental protection. However, at the same time, biological invasions, which in part created the need for pesticides, continue in spite of federal efforts to exclude foreign pests from other countries. In recent years, this silent invasion has alarmed scientists worldwide and prompted federal officials in the United States to work together to address the problem. Environmentally sound approaches and techniques for weed prevention and early control are necessary prerequisites in the battle against invasive plants.