G. Delchev*, M. Georgiev

Department of Plant Production, Faculty of Agriculture, Trakia University, 6000 Stara Zagora, Bulgaria

Abstract. Herbicides combinations and tank mixtures of herbicides with adjuvants, fertilizers, growth regulators, fungicides, insecticides, are more effective than when applied alone on wheat crops. Their combined use often leads to high synergistic effect on yield. Many authors present data from which it is clear that durum wheat differs from common wheat in their reaction to some herbicides, herbicide combinations and herbicide tank mixtures. A serious problem in wheat is Bromus arvensis L. due to their resistance to most antigramineous herbicides. In recent years effective herbicides to fight against them have emerged, but their number is still too limited. A problem is the persistence of some herbicides used in the predecessors on succeeding crops, which is directly related to the weather conditions during their degradation. Contrary opinions are published on some issues due primarily to the different conditions under which the experiments were conducted and the biological characteristics of the tested cultivars. Most of the information on these subjects refers mainly to common wheat and only a limited amount of it is for durum wheat. A serious problem is also the volunteers of Clearfield canola (Brassica napus L.), Clearfield and Express sun sunflower (Helianthus annuus L.). They have resistance to herbicides different from that of conventional canola and sunflower hybrids. A problem is also volunteers of coriander (Coriandrum sativum L.) and milk thistle (Silybum marianum Gaertn.). There is yet no information in the scientific literature as to control of these volunteers.