| Recently, the protection of non-target plant species, including endangered and threatened species, has become an important issue in the area of pesticide registration in the USA. Pesticide registration is based on toxicity tests developed by the Office of Prevention, Pesticides and Toxic Substances (OPPTS), US Environmental Protection Agency (EPA); however, these tests use agricultural crop species such as corn or soybean for extrapolation to all non-target terrestrial plant species. Some of these species have been bred for more than a thousand years. This research asks the question: are non-target plant species being protected under this system using agricultural crops as surrogate test species? Standard phytotoxicity tests adapted from the OPPTS guidelines were used to compare the sensitivities of current plant test species with the wild variety within the same species and genus, for example, corn (Zea mays var. mays) and teocinte ( Z. mays subsp. mexicana, Z. mays subsp. parviglumis, and Z. luxurians). Results suggest that plants have different sensitivities to herbicides, even within the same species. There is no "one most sensitive species" for all chemicals. Results from standardized phytotoxicity tests with agronomic species may not adequately protect non-target species, suggesting that a wider variety of plant species in addition to crop species may be needed for a large enough database of pesticide toxicity data to develop species sensitivity distributions for use in pesticide registration in the USA. Also, the inconsistency of results between chemicals may suggest that species selection for non-target plants may need to be chemical specific, resulting from an ecological risk assessment type selection process. |
