Alternatives to Diclofop for the Control of Italian Ryegrass (Lolium multiflorum) in Winter Wheat (Triticum aestivum)1

Abstract

Field studies were conducted to evaluate the tolerance of Italian ryegrass and the metribuzin-sensitive winter wheat cultivar Dozier to metribuzin, chlorsulfuron, flufenacet plus metribuzin, chlorsulfuron plus metsulfuron, diclofop, and combinations of these herbicides applied preemergence (PRE) and postemergence (POST) to wheat in the two- to three-leaf (2–3 LF) at Feekes' stage 1 and to one to two tiller wheat (TILL) at Feekes' stage 3. Italian ryegrass control was 80% or greater with diclofop at all rates and application timings; flufenacet plus metribuzin PRE at all rates; metribuzin POST at 2–3 LF at all rates; and chlorsulfuron or chlorsulfuron plus metsulfuron PRE followed by (fb) metribuzin POST at 2–3 LF. Control of 2–3 LF Italian ryegrass was inconsistent with flufenacet plus metribuzin, chlorsulfuron, and chlorsulfuron plus metsulfuron. Italian ryegrass control was poor with flufenacet plus metribuzin TILL, metribuzin PRE, and metribuzin TILL. Metribuzin applied alone and after chlorsulfuron or chlorsulfuron plus metsulfuron injured wheat. Wheat recovered from flufenacet plus metribuzin injury. However, injury from metribuzin at 280 g ai/ha PRE, 2–3 LF, and at 420 g/ha, 2–3 LF, resulted in season-long injury. Yields were significantly reduced because of metribuzin (PRE, 2–3 LF, or TILL) injury and also by chlorsulfuron or chlorsulfuron plus metsulfuron (PRE) fb metribuzin (2–3 LF).Nomenclature: Chlorsulfuron; diclofop; flufenacet; metribuzin; metsulfuron; Italian ryegrass, Lolium multiflorum Lam. #3 LOLMU; winter wheat, Triticum aestivum L. # TRAES ‘Dozier’.Additional index words: Soft red winter wheat, wheat injury, wheat yield.Abbreviations: COC, crop oil concentrate; DAP, days after planting; fb, followed by; 2–3 LF, two- to three-leaf stage at Feekes' stage 1.5; NIS, nonionic surfactant; POST, postemergence; PRE, preemergence; TILL, wheat tillered at Feekes' stage 3.