Toxicity testing of fifteen non-crop plant species with six herbicides in a greenhouse experiment: implications for risk assessment.

Estimation of risk to plants not targeted by herbicides when used in agricultural or forestry situations requires appropriate data on multiple species. Currently, many questions remain unresolved as to the adequate type and number of species to be tested. This paper presents the result of a unique greenhouse experiment where testing was performed with 15 non-crop plant species sprayed with 6 herbicides. The herbicides were chosen because of their different modes of action and because they are widely used in several countries. The plants favoured were species commonly found in field margins of Europe and/or North America. This dataset (called thereafter Danish/Canadian) was compared to the crop species that had been submitted to the US EPA for the same herbicides. In general, the selected plant species in the Danish/Canadian database were easy to grow and maintain in the greenhouse. The Danish/Canadian plants were overall more sensitive than the species tested in the US EPA data, yielding to a 5% protection threshold (HC5(50)) that was always more conservative. There was a large variability in plant responses among herbicides. Recommendations are provided on species that should and should not be used for risk assessment of non-target plants.