Clodinafop, a new herbicide for the selective control of grass weeds in wheat. I. Control efficacy on wild oats (Avena fatua), annual ryegrass (Lolium multiflorum), dogtailgrass (Cynosurus echinatus), and bulbous oatgrass (

Juan Ormeño N.1 y Jorge Díaz S.2

Clodinafop, a new herbicide for the selective control of grass weeds in wheat, was evaluated in field and pot trials conducted at the Regional Research Center La Platina (INIA) in Santiago (33º 34' S) and at the Regional Research Center Carillanca in Temuco (38º 41' S). Control efficacy on Chile's most important annual and perennial grass weeds, namely, wild oats (Avena fatua L.) (AVEFA4), annual ryegrass (Lolium multiflorum L.) (LOLMU), dogtailgrass (Cynosurus equinatus) (CYXEG), and bulbous oatgrass (Arrhenatherum elatius Presl. spp. bulbosum (Willd.) Hyl.) (ARRES) was assessed. Different clodinafop rates from 40 to 80 g/ha applied at growth stages ranging from 2 true-Ieaves or 12-13 of Zadock's scale of growth until the end of tillering or stage 30-31 of the weeds were tested in pot and field experiments. Clodinafop applied at different rates was effective to control annual grasses only when sprayed at early growth stages but failed to control weeds at stage 30-31. Similar results were obtained in field trials where rates of 40, 50, 60, 70 and 80 g/ha were tested. In field tests at Carillanca, clodinafop effectively controlled dogtailgrass, wild oats and Italian ryegrass, but failed on bulbous oatgrass as new shoots arose from treated plants. Herbicide susceptibility decreased in the following order: dogtailgrass, wild oat, annual ryegrass and bulbous oatgrass. These results indicated that rates of clodinafop ranging from 60 to 80 g/ha and sprayed at early or before full tillering of the weeds were effective to selectively control the three annual grass weeds and to suppress temporarily bulbous oatgrass.

Keywords: grass herbicide, wheat, clodinafop, wild oats, AVEFA, annual ryegrass, LOLMU, dogtailgrass, CYXEG, bulbous oatgrass, ARRES.
1 Centro Regional de Investigación La Platina (INIA), Casilla 439, Correo 3, Santiago, Chile.
2 Centro Regional Carillanca (INIA), Casilla 58-D, Temuco, Chile.
3 Abreviaciones de especies de malezas de acuerdo a la Iísta de códigos computarizados de 5 digitos recomendado por Bayer (1992) y la Sociedad Americana de Malherbologia (W.S.S.A.).