This work was carried out at Araruna, PR - Brazil, to evaluate the tolerance of five cassava cultivars (Espeto, Mico, Fécula Branca, IAC-14, and Fibra) to different herbicides. Treatments evaluated were check (no herbicide), metribuzin (0.49 kg a.i. ha-1), clomazone (1.00 kg a.i. ha-1), formulated mixture of ametryn + clomazone (2.50 kg a.i. ha-1) and ametryn + trifluralin (1.50 + 1.80 kg a.i. ha-1). All treatments were maintained weed free during the entire crop cycle. The experiment was arranged in a factorial scheme (5²), randomized block design. Tolerance was evaluated based on phytotoxicity symptoms, crop stand, height and yield. Ametryn + trifluralin was the most selective treatment applied to cassava and only the formulated mixture of ametryn + clomazone caused visual symptoms of injury in the Mico and Fécula cultivars, at 51 days after planting. No chemical treatments affected cassava stand or height. The highest root yields were achieved by the cultivars Fécula Branca and IAC-14.
selectivity; phytotoxicity; metribuzin; ametryn; trifluralin; clomazone
