Evaluation of Herbicides Used in the Preemergence to the Portulaca oleracea Control

Abstract

Portulaca oleracea is found intervening in several crops mainly vegetables, besides crops like sugar cane and cotton. The study was developed with the objective of improving the recommendation of herbicides alternatives in pre emergency used on cotton crop, for controlling P. oleracea. The work was conducted in two stages in greenhouse conditions: the first to establishing, through dose-response curve, herbicides rates able to promote efficient control of P. oleracea; the second one, to verify the period of residual activity provided by herbicides rates considered efficient and selected in the first stage, and by recommended rates. In the first stage, increasing rates of alachlor, diuron, clomazone, oxyfluorfen, pendimethalin, prometryn, smetolachlor, trifluralin 600 and trifluralin 450 herbicides were used. In the second stage, an effective rate and a recommended one of each herbicide were applied in four periods preceding weeds sowing, evaluating control percentage at 0, 10, 20 and 30 days after treatments application (DAA). It was verified, in the first stage, that herbicides efficiently controlled P. oleracea species, with exception of two trifluralin formulations. However, the effective rates (C95) of alachlor and prometryn showed short residual activity, as observed in the second stage. Recommended rate of prometryn promoted the efficient control up to 30 DAA, unlike to alachlor. Diuron, pendimethalin, oxyfluorfen, s-metolachlor in both rates used, besides trifluralin 600 and clomazone in recommended rates, showed effective residual activity for periods up to 30 DAA, to sandy clay loam texture soil.