Assessing the extent and effects of herbicide drift into Danish hedgerows

Very low dosages of herbicides are known to cause effects on bird cherry (Prunus avium) and hawthorn (Crataegus monogyna). It is not yet known whether other hedgerow trees and shrubs are equally sensitive to herbicide drift, to which extent spray drift into hedges and other habitats close to fields occurs, and which consequences spray drift may have for the fauna associated with such habitats. We approached these questions by combining measures of spray deposition in a hawthorn hedgerow under different weather conditions with observations of effects on three different hedgerow species. Spraying was performed with a common tractor sprayer in five tracks parallel to the hedgerow, and either the herbicide metsulfuron methyl in combination with the dye fluorescein or fluorescein alone was applied. Deposition in the hedgerow and 12-48 m into the field was measured. Herbicide effects on hawthorn fruit set were assessed. Metsulfuron methyl effects on Sambucus nigra (elder) and Sorbus intermedia were studied in separate experiments and will include second year effects. Methods and preliminary results are presented and discussed in relation to pesticide regulation.