The objective of this study was to investigate the tolerance levels of wheat and oat cultivars to the herbicide diclofop-methyl, fenoxaprop-ethyl and haloxyfop-methyl, aiming the selective use of these chemicals to control grass species that may infest these crops. Two experiments have been performed, one at field condition and another in the greenhouse. Treatments tested in the field were diclofop-methyl at 540 g/ha, fenoxaprop-ethyl at 180 g/ha, haloxyfop-methyl at 120 g/ha, plus a check without herbicide treatment, applied on Avena sativa cultivars 'CTC-1', 'UFRGS-7' and 'UPF-16', and on Avena strigosa. In the greenhouse experiment, three rates of fenoxaprop-ethyl (0, 90 and 120 g/ha) have been tested, applied on seven wheat cultivars ('BR-23', 'BR-35', 'BR-38', 'E-16', 'E-40', 'E-49' and 'E-52'), on aots, Avena strigosa and ryegrass. As results of field trial, it was detected that all herbicides tested controlled efficiently (over 90%) oat cultivars. Avena strigosa showed high sensitivity to fenoxaprop-ethyl and haloxyfop-methyl, and some tolerance to diclofop-methyl, whereas wheat showed tolerance to diclofop-methyl and fenoxaprop-ethyl. In the greenhouse, wheat cultivars 'BR-38', 'E-16', 'E-49' and 'E-52' presented cceptable levels of injury to fenoxaprop-ethyl at 90 g/ha, while the other cultivars ('BR-23', 'BR-35' and 'E-52') presented moderate injury to the herbicide. On the other hand, fenoxaprop-methyl at 120 g/ha caused increased injury levels to all wheat cultivars, except 'E-16' and 'E-52'. Ryegrass showed tolerance to fenoxaprop-ethyl . It was concluded that it is possible to use fenoxaprop-ethyl herbicide in wheat fields for selective controle of oats and A. strigosa. Diclofop-methyl presents high levels of oats control, but reduced control of A. strigosa. Haloxyfop-methyl did not prove selective for wheat, controlling with efficiency the grasses tested.
Diclofop-methyl; feno-xaprop-ethyl; haloxyfop-methyl; oats; ryegrass; wheat