Evaluacion preliminar de tres nuevos herbicidas posemergentes en yuca (Manihot esculenta Crantz)

Se evaluaron la selectividad y la eficiencia en el control de gramineas y malezas de hoja ancha de 3 herbicidas (fenoxapropetil, glufosinate y mefluidide) y la mezcla de paraquat + oxifluorfen en yuca var. Mexico 11. Las malezas predominantes fueron Leptocloa filiformis, Eleusine indica, Portulaca oleracea, Euphorbia hypericifolia, Eu. hirta, Borreria laevis, Amaranthus dubius, Corchoris orinosensis, Ipomoea sp., Phyllanthus amarus y Cyperus spp. El indice de dano (ID) se cuantifico desde 0 (ningun dano) hasta 10 (plantas muertas). Se utilizo un diseno de parcelas subdivididas con 3 repeticiones para evaluar tanto la epoca de aplicacion (21, 36 y 51 dias despues de la siembra) como nivel o dosis de aplicacion de cada producto. La epoca de aplicacion a los 51 dias presento los mas altos ID; a los 21 y 36 dias no hubo diferencia apreciable. Mefluidide causo el menor ID en ambas dosis y durante las 3 epocas de aplicacion, especialmente a los 21 y 36 dias, con niveles de 1360 g i.a./ha. Paraquat + oxifluorfen causo los mayores ID (2.5, 3.0 y 3.2) en las distintas epocas, en dosis de 960 + 960 g i.a./ha. De los 4 tratamientos, glufosinate, fenoxapropetil y mefluidide no danaron en forma apreciable el cultivo, aplicados a los 21 y 36 dias. Se logro un buen control de malezas gramineas y de hoja ancha, con 800 g i.a. de glufosinate/ha a los 36 dias, en tanto que a los 21 dias funciono mejor la mezcla de paraquat + oxifluorfen, con 480 + 480 g de i.a./ha. El control de Cyperus spp. con 800 g de i.a. de glufosinate/ha alcanzo valores del 63 por ciento. (CIAT)

The selectivity and efficiency of control of grasses and broadleaf weeds of 3 herbicides (ethyl-phenoxaprop, gluphosinate, and mefluidide), and the mixture of paraquat + oxyfluorfen were evaluated in cassava var. Mexico 11. Predominant weeds were Leptocloa filiformis, Eleusine indica, Portulaca oleracea, Euphorbia hypericifolia, Eu. hirta, Borreria laevis, Amaranthus dubius, Corchoris orinosensis, Ipomoea sp., Phyllanthus amarus, and Cyperus spp. The damage index (DI) was estimated using a scale from 0 to 10, where 0 = no damage and 10 = dead plants. A split-split plot design was used with 3 replications to evaluate both the application date (21, 36, and 51 days after planting) and application rate of each product. The highest DI were obtained when products were applied at 51 days; no significant difference was observed at 21 and 36 days after planting. Mefluidide caused the lowest DI at both rates and for the 3 application dates, especially at 21 and 36 days, with 1360 g a.i./ha. Paraquat + oxyfluorfen produced the highest DI (2.5, 3.0, and 3.2) for the different dates at rates of 960 + 960 g a.i./ha. Of the 4 treatments, gluphosinate,ethyl-phenoxaprop, and mefluidide caused no considerable damage to the crop when applied at 21 and 36 days after planting. Good control of grasses and broadleaf weeds was achieved with 800 g a.i. gluphosinate/ha at 36 days, while at 21 days the mixture paraquat + oxyfluorfen at 480 + 480 g a.i./ha performed best. Cyperus spp. control with 800 g a.i. gluphosinate/ha reached levels of 63 percent. (CIAT)