Usage of systekic herbicides for controlling grass (Cynodon nlemfluensis) in a macadamia orchard

En Arenal, provincia de Guanacaste, en un huerto de macadamia de cinco años de edad, sembrado a 7 m x 7 m, se realizó un experimento con el fin de identificar un tratamiento químico que permitiera combatir estrella africana sin afectar la macadamia. Los tratamientos evaluados fueron: glifosato 0,72 y 1,2 kg i.a./ha; haloxifop-metil 0,09 y 0,13 kg i.a/ha; clethodim 0,09 y 0,13 kg i.a./ha; fenoxaprop-etil (isómero) 0,09 y 0,13 kg i.a.jha; fluazifop-butil 0,09 y 0,13 kg i.a./ha; testigo deshierbado cada mes y testigo a libre crecimiento de malezas. Ninguno de los tratamientos mostró toxicidad a la macadamia. El mejor combate de estrella africana se logró con glifosato 1,2 kg/ha y haloxifop-metil 0,13 kg/ha.An assay was conducted in a five year old macadamia (Macadamia integrifolia) orchard, planted at 7 m x 7 m, in order to identify the chemical treatment which best controlled the grass, in Arenal - Guanacaste, Costa Rica. The treatments applied were: glyphosate at 0.72 and 1.2 kg a.i./ha, haloxyfop-methyl at 0.09 and 0.13 kg a.i./ha, clethodim at 0.09 and 0.13 kg a.i./ha, fenoxaprop-ethyl (isomer) at 0.09 and 0.13 kg a.i./ha, fluazifop-butyl at 0.09 and 0.13 kg a.i./ha, and once a month weeding and unweeding controls. None of the treatments caused phytotoxicity symptoms to the macadamia. The herbicides were applied, with an experimental CO2 operated sprayer and a 800050 nozzle, in 1.5 m wide strips along the macadamia trees, at a rate of 113 l/ha. At the application time, the grass was 0.6 m high and a covering of 90%. The glyphosate at arate of 1.2 kg a.i./ha showed a grass control of 90 % even at 14 weeks after the application, but at 0.72 kg a.i./ha was effective only during the first ten weeks. The haloxyfop-methyl at a rate of 0.13 kg a.i./ha had a similar behavior as the glyphosate during the first eight weeks after application, when the grass started to sprout again. The effect of the remaining treatments was lesser in controlling this grass.UCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias Agroalimentarias::Estación Experimental Agrícola Fabio Baudrit Moreno (EEAFBM