Weeds control with herbicides applied in pre-emergence in potato cultivation= Controle de plantas daninhas com herbicidas aplicados em pré-emergência na cultura da batata

Abstract

There are few pre-emergent herbicides that are selective and registered for potato crop. Thus, this study aimed to evaluate the control of weeds with pre-emergent herbicides, as well as their effects on potato crop. The treatments consisted of a control, a hoed control (manual weed removal), metribuzin (240 g ha^-1), linuron (450 g ha^-1), diclosulan (25,2 g ha^-1), imazetapir (700 g ha^-1), prometryn (1000 g ha^-1), clomazone + carfentrazone (300 + 7.5 g ha^-1), clomazone + carfentrazone (600 + 15 g ha^-1) and sulfentrazone (125 g ha^-1). A randomized complete block design (RCB) was used with four replications. Largest stem, phytotoxicity, and weed control were measured at 10 and 30 days after stem emergence (DAE), which coincided with the periods before and after hilling, respectively. Soluble solids content, yield and tuber classification were determined after harvesting. The results were compared by a Tukey test (5% significance). The evaluated herbicides did not affect the number of stems per meter and length of the largest stem. Regarding weed control, clomazone + carfentrazone (600 + 15 g ha^-1) controlled C. benghalensis (Behghal dayflower), E. heterophyla (milkweed) and R. raphanistrum (wild radish), better than the other herbicides, which provided little control over E. heterophyla and R. raphanistrum. The strongest symptoms of phytotoxicity were observed with metribuzin, diclosulan and imazethapyr, which were also associated with lower levels of soluble solids, total yield, and yield of "special" tubers. Therefore, these herbicides were considered less selective. Linuron and clomazone did not produce phytotoxicity, did not affect levels of soluble solids, and did not reduce total or "special" tuber yield, and were thus considered more selective for this potato cultivar.