Clodinafop, a new herbicide for the selective control of grass weeds in wheat. II. Selectivity on spring and alternative cultivars.

Juan Ormeño Núñez1 y Jorge Díaz Sánchez

Four field trials were conducted during 1990/91 and 1991/92 seasons in the Central and Southern areas of Chile in orderto evaluate the selectivity of 39 spring and alternative wheat cultivars to single postemergence applications of clodinafop, a new selective grass weeds herbicide. The formulation Clodinafop 240 g/L EC was used at rates of 42, 84, 168 and 240 g/ha. A non-commercial formulation ofclodinafop 80 giL EC was also used at similar rates. Data indicates that Clodinafop rates approaching the maximum recommended did not affect crop plants whereas sorne initial chlorosis and stunting was observed in overdose treatments. However, these adverse effects were of a transient nature and undetectable 60 days after spraying. Out of39 wheat cultivars tested none appeared susceptible in terms ofearly visual assessments, and only Millaleu, Maqui, Ucaro-1 and Ucaro-2 showed plantheight reductions. Other variables measured to determine clodinafop selectivity, such as plant height at 60 days after spraying, spikes/m2 , 1,000 grain weight, grains/spike, grain yield (qqm/ha), and hectoliter weight were unaffected by normally recommended rates of application of the herbicide, during the first or second year at each locality. Doubling and quadrupling these rates affected 3 and 5 cultivars, respectively, and only the spring cultivar Millaleu consistently showed lower selectivity to an overdose of the herbicide.

Keywords: Clodinafop, wheat selectivity, grass herbicide, Tríticum aestivum, Tríticum
1 Instituto de Investigaciones Agropecuarias, Centro Regional de Investigación La Platina, Casilla 430, Correo 3, Santiago, Chile. jormeno@inia.cl.