Cassava cultivars sensibility to mesotrione herbicide

Abstract

Unsuitable weed management is one of the main factors responsible for low mean yield of cassava (Manihot esculenta Crantz) in Brazil. In this crop, mechanical weed control is the most commonly used, due to the lack of registered herbicides for cassava crop. In the search for alternatives to this problem, this work aimed to evaluate the tolerance level of cassavas cultivars to mesotrione herbicide applied in post emergence. A experiment was conducted, in green house conditions, in randomized blocks with four replications. A factorial scheme 5x5 was adopted, consisting of the combination of five dosages of mesotrione herbicides and five cassava cultivars. Intoxication of cassava plants, height, stem diameter and number of leaves of plants were evaluated weekly and 35 days after application (DAA) plants were harvested for determining dry matter and leaf area.n. The highest values for visual intoxication were observed at 14 and 28 days after the herbicide application (DAA) and caused by the highest doses of mesotrione herbicide. These symptoms consisted of whiteness in new leaves.  At 35 days, plants showed signals of recovery, mainly due the sprout of new leaves. The herbicide did not affected the height, stem diameter, number of leaves, foliar area and dry matter accumulation of leaves, stems, roots and in total characteristics, in any of the evaluated doses. This is an evidence of cassava cultivars tolerance to mesotrione herbicide.