Differential Tolerance of Two Species of the Genus Digitaria to Herbicide Recommended for Sugarcane Crop

The chemical control of crabgrass can be poor depending on the species composition of species in the area. It is known that there is a fault in the control of Digitaria nuda in places where applications of photosystem II inhibitors herbicides by long-time, being necessary to better understand how this tolerance work. The aim of this study was to develop dose-response curves for D. nuda (tolerant) and D. ciliaris (susceptible), with recommended herbicides for sugarcane crop used alone or in mixtures. The experiment was carried out in a greenhouse with the pre-emergence application of diuron + hexazinone, ametryn and mixture of both in increasing doses. The doses were 0; 6,25; 12,5; 25; 50; 100; 200 and 400% of the label for sugarcane diuron + hexazinone (936 +264 g ai ha-1), ametryn (2500 g ai ha-1) and the combination of two herbicides in the same proportions. What can be concluded that application of ametryn in isolation produced similar levels of control in both species. The association of ametryn with the herbicide diuron + hexazinone caused synergistic effect for the control of D. nuda, but for D. ciliaris the effect was antagonistic evaluated by methods.