Revista Brasileira De Herbicidas 2002; 3(2-3): 127-132
Dose of economical injury of cyanazine in corn
The tolerance of the com crop to the herbicide cyanazine depends on the growth stage of the crop. An experiment was conducted in Eldorado do Sul, RS, Brazil, to evaluate the selectivity of cyanazine applied at different rates on com, and at different growth stages, to estimate the economic impact of crop injury caused by the herbicide. The com hybrid AG 501 was planted on a no-till system where the weed control was performed with preemergence herbicides. Treatments tested were combinations of cyanazine (rates of 0.0, 2.0 and 2.5 kglha) at different growth stages (V3, V6 and V). Cyanazine selectivity decreases after the com crop reaches the six leaf stage, and with herbicide rates superior to 2.0 kglha. The rate of economic injury, that is, the herbicide rate which the benefit of the weed control is equivalent to the yield loss due to weed competition, reduces with the reduction of the economic impact of the weed on the crop, and with increased com price. These results suggest that when the weed infestation is almost above the weed economic threshold, the economic impact of the herbicide injury is higher than at high weed densities.
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