Many herbicides that control broadleaf weeds in wheat can antagonize grass herbicide efficacy, resulting in less grain yield due to competition. Also, the broadleaf herbicide carfentrazone-ethyl can injure wheat, leading to less grain yield because of physiological response. Experiments were conducted to evaluate carfentrazone-ethyl antagonism of fenoxaprop-ethyl, tralkoxydim, clodinafop-propargyl, imazamethabenz, and flucarbazone-sodium and injury to wheat with tank mixes of carfentrazone-ethyl plus each grass herbicide or thifensulfuron, tribenuron, metsulfuron, or imazamox. Carfentrazone-ethyl did not adversely affect control of wild oat or yellow foxtail by grass herbicides in wheat. Carfentrazone-ethyl alone caused 21% wheat injury 3 d after treatment. Adding flucarbazone-sodium to carfentrazone-ethyl resulted in the least wheat injury among treatments that included carfentrazone-ethyl. Fenoxaprop-P-ethyl or clodinafop-propargyl with carfentrazone-ethyl also resulted in less wheat injury compared with carfentrazone-ethyl alone, which was attributed to formulation safeners. Sulfonylurea herbicides provided safening of carfentrazone-ethyl similar to flucarbazone-sodium, while imidazolinones did not alleviate injury. Tralkoxydim plus carfentrazone-ethyl gave 28% wheat injury compared with 21% from carfentrazone-ethyl alone. Wheat injury was no longer visible by 20 d after treatment, and wheat yield was not affected by carfentrazone-ethyl injury when wild oat and yellow foxtail were present or controlled with herbicide.
Nomenclature: Carfentrazone-ethyl; clodinafop-propargyl; fenoxaprop-P-ethyl; flucarbazone-sodium; tralkoxydim; yellow foxtail, Setaria glauca (L.) Beauv. #3 SETLU; wild oat, Avena fatua L. # AVEFA; wheat, Triticum aestivum L. ‘Alsen’, ‘ND722’, ‘Oxen’.
Additional index words: Antagonism, crop injury, safening with herbicides, imazamethabenz, imazamox, thifensulfuron, tribenuron, metsulfuron.
Abbreviations: ALS, acetolactate synthase (EC 220.127.116.11); COC, crop oil concentrate; DAT, days after treatment; MSO, methylated seed oil; NIS, nonionic surfactant; PO, petroleum oil; UAN, urea and ammonium nitrate solution.