In 1985–2002 thirteen weeds resistant to atrazine were selected by a repeated application of triazine herbicides on arable land, in orchards, non-agricultural land and at railways in the Czech Republic. Recently Digitaria sanguinalis biotypes resistant to atrazine have been found at three railway junctions. Long-lasting application of the active ingredient imazapyr at railways caused selection of resistant Kochia scoparia biotypes. High resistance to chlorsulfuron has been discovered in five Apera spica-venti biotypes originating in winter cereals fields. The molecular basis of resistance to atrazine has been identified in the following weeds: Kochia scoparia, Solanum nigrum, Senecio vulgaris, Conyza canadensis, Digitaria sanguinalis, Amaranthus retroflexus and Chenopodium album. The resistance was conferred by a glycine for serine substitution at residue 264 of the D1 protein in all of those weeds. The resistance to imazapyr in Czech Kochia scoparia biotypes was conferred by a mutation at codon 574 of the ALS gene. Analysis of the results of DNA sequencing indicated, that the mutation induced a leucine for tryptophane substitution. There was excellent correspondence between the phenotypic resistance to herbicides of individual plants and the presence of mutations.

Some active ingredient of herbicides, after application, can create a risk for ground and surface water. The aim of investigations was monitoring of herbicidal pollution in ground and surface water on arable areas. The investigations were conducted in the years 2000-2002. The samples were collected (from stationary points located in the south-west Poland) twice a year (in spring and autumn about 3-6 weeks after nominal term of herbicide application). Surface water was sampled in 27 points and ground water in 18 wells. The residues of herbicide active ingredients (triazine and phenoxy acids) were determined using HPLC methods with UV detection and GLC method with ECD detection. The residues of active compounds in surface water (in spring and autumn) were detected. Residues at concentrations exceeding the EU safety standards were detected most frequently in springtime. The contamination levels in excess admissible limits were found in ca. 15% of surface water samples. In ground water (from wells) residues were detected sporadically and its level was very low (ca. 0.01- 0.1 mg=dm").