Interferência e nível de dano de arroz-daninho em arroz cultivado

Abstract

Weedy rice is considered one of the main weeds that infest rice-growing areas and limits the productive potential of irrigated rice (Oryza sativa). Because cultivated rice and weedy rice belong to the same species, chemical control is limited, and its management is challenging. The knowledge about the ecophysiological aspects of weedy rice is one of the keys to adopting control measures only when they are profitable or necessary. In this sense, current studies are essential to assist the producer in management strategies that favor the competitive ability of the crop. Thus, three studies were carried out: 1) To determine the periods of interference of the weedy rice with the irrigated rice crop; 2) To evaluate the competitive ability of the cultivar BRS Pampa CL with weedy rice susceptible and resistant to imidazolinones; and, 3) Determining the economic threshold level in cultivated rice. The results demonstrate that the critical period of control of weedy rice is between 8 to 14 days after the emergence of the crop. In the competition with the crop, the resistant biotype was less competitive in the increase of dry mass of the part area (DMPA) and the susceptible biotype showed superior competitive ability for the leaf area (LA). In general, intraspecific competition between cultivated rice and weedy rice was more harmful to the development of both. The population of weeds from which the level of economic damage to the crop occurs ranged from 0.7 to 2 plants m-2.