Development of a field bioassay for the side-effects of herbicides on vascular plants using Brassica napus and Poa annua.

A field bioassay method has been developed for assessing side-effects of herbicides on Brassica napus and Poa annua. The test method aims at effects outside the target area, up to 20 m from the treated parcel. Experiments were conducted in the field and in a glasshouse with the herbicides atrazin, bentazone, diquat, glyphosate, and r(4-chloro-2-methylphenoxyacetic acid) MCPA. An iterative procedure was used with the aim of developing a sound test procedure. The resulting method appeared to be very sensitive. Pesticide drift was measured using water-sensitive paper. Effects were sometimes found below the detection limit of this method (at 8 m from the treated parcel with moderate wind speeds of 3-5 m/s). The sensitivity of the test and the test conditions are discussed and an optimized method is presented.