Sensitivity of Winter Wheat Cultivars to Selected Herbicides

The experiments on tolerance of winter wheat cultivars to herbicides were performed under field conditions during 2003-2005 in the region of Wroc aw (South-West of Poland). Five cultivars were examined (Zyta, Tonacja, Sukces, Clever, Kobra). Two herbicide mixtures: isoproturon + pendimethalin and diflufenican + flurtamon were applied in the autumn, in stage of 3-4 leaves. In the spring, when wheat reached stage of full tillering, the following herbicides were used: florasulam + 2.4-D and fluroxypyr + 2.4-D. Phytotoxicity of herbicides was determined on the base of plants vigour assessment, plants counting, yield and some yield components. During the experimental period, impact of the mixture pendimethalin + isoproturon on grain yield of Clever cultivar was observed only in the season with hard winter conditions (2002/2003). The remaining varieties: Zyta, Tonacja, Sukces and Kobra were completely tolerant to this herbicide mixture. Mild winter seasons did not show a negative influence of herbicides on grain yield of tested varieties. All cultivars showed a complete tolerance to diflufenican + flurfamon and florasulam + 2.4-D. The mixture fluroxypyr + 2.4-D caused ear deformation of all tested wheat cultivars, but did not affect negatively grain yield.