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Submodule 1: What are invasive weeds?
Predicting Invasiveness of Plants
It is estimated that there are roughly 1,500 “weeds” established in the U.S., with many of these infesting western rangelands. Scientists estimate that there are over 20,000 potentially invasive plants that have not yet entered the U.S., which suggests that the possibility for more infestations is high. As seen from the list of common invasive plant growth characteristics, there is a lot known about plants that have already become invasive. The problem is that beforehand no one knows exactly which plants will actually become invasive. This situation illustrates the need to be vigilant regarding which plants enter the country and to have well-trained inspectors screening imported plants.
The Animal and Plant Health Inspection Service’s (APHIS) Plant Protection and Quarantine (PPQ) program is the agency that is primarily responsible for regulating the importation of potentially noxious plants and their seeds into the U.S. PPQ http://www.aphis.usda.gov/ppq/ requires permits for the importation and transit of plants and plant products under regulatory authorities. There are actually very few plants whose importation is restricted; this primarily applies to plants that are already known invaders whose spread via further importation is restricted. The scope of work of APHIS is expanding and now also involves the exportation of plants from the U.S. to other countries. Through the International Services and Trade Support Team (IS/TST), work outside the U.S. includes surveillance of plant infestations in other countries to decrease the chances of importation of these invasive plants into the U.S. In addition, the IS/TST helps to ensure that agricultural exports are compliant with regulations with U.S. trading partners, thereby preserving agricultural commodities trade. In practice, the chief function of APHIS and its numerous programs is to restrict the movement of plant pests into this country.
Diffuse knapweed (photo courtesy Larry Howery)
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