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.

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The use of ecotoxicity test results obtained in the laboratory for prediction of effects of potentially toxic concentrations of chemicals in the field is hampered by several factors differing between the laboratory and the field situations. One important factor is the binding of test chemicals to soil, which is affected by the age of the contamination and soil type. The present study investigated the effect of contamination age by introducing an aging period of 1 to 12 weeks between mixing the test substance, copper sulfate, in with soil and introducing the test plant, Fallopia convolvulus (L.) A. Löve. Copper accumulation, emergence of cotyledons, and growth were assessed and related to total (boiling with HNO(3)) and 0.01 M CaCl(2)- and DTPA-extractable soil copper concentrations. Aging of the copper-contaminated soil had only small effects on bioaccumulation of copper, copper toxicity, and extractable soil copper fractions. Soil copper had no effect on emergence of cotyledons. Estimated EC(50) values for shoot and root growth averaged 280 mg Cu/kg. Effects on growth in these laboratory-treated soils were much more severe than in a study performed in soil from an old copper-contaminated field site. Neither CaCl(2)- nor DTPA-extractable copper fractions could explain all of the differences in effects between aged spiked soil and field soil. The accumulation pattern for roots and shoots of F. convolvulus indicated that excessive copper was accumulated and adsorbed mainly by the fine roots, whereby the copper concentrations of other plant parts were kept low until the plant was no longer able to maintain this regulation. An internal threshold for effects on growth of about 20 mg Cu/kg shoot dry weight was estimated, coinciding with a soil copper concentration of approximately 200 mg/kg.

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Summary1. The probability of a transgenic crop establishing a feral population outside cultivated areas and possibly outcompeting naturally occurring species needs to be assessed to make an ecological risk assessment of the transgenic crop. 2. The interaction between herbivory and competition is thought to determine the ecological success of insect-resistant plants, and this interaction was investigated in a competition experiment with transgenic insect-resistant Bt-Brassica napus, Brassica rapa, Lolium perenne, and herbivory from the large white butterfly Pieris brassicae. 3. As expected, herbivory had a negative effect on the biomass of B. rapa at high plant densities. The competitive ability of L. perenne, when growing with B. rapa, increased significantly with the level of herbivory on B. rapa. 4. To predict the effect of herbivory in a natural ecosystem, plant competition between the two annual Brassica species was analysed in a population ecological model. It was concluded that it is probable that transgenic Bt-B. napus plants may invade a natural habitat if herbivory is sufficiently high and the habitat is suitable for B. napus. 5. Synthesis and applications. The results indicate that it is important to study the interaction between herbivory and competition when assessing the ecological risk of insect-resistant genetically modified crops. Furthermore, combining ecological data from manipulated experiments with population ecological modelling is a fruitful approach when conducting environmental risk assessments.