Spring Wheat Response to Herbicides Applied at Three Growth Stages

Abstract

AbstractSince the inception of 2,4‐D [(2,4‐dichlorophenoxy) acetic acid], many herbicides have been developed for broadleaf weed control in wheat (Triticum aestivum L.). However, many of these herbicides have not been thoroughly evaluated with respect to application timing and effects on wheat yield and quality. Field studies were conducted at Torrington, WY on a Bayard fine sandy loam (coarse loamy, mixed, mesic Torriothentic Haplustoll) in 1984 and 1985 to evaluate the response of ‘Oslo’ spring wheat to 10 broadleaf herbicide treatments applied at three growth stages. Dicamba (3,6‐dichloro‐2‐methoxybenzoic acid), dicamba plus 2,4‐D and dicamba plus MCPA [(4‐chloro‐2‐methylphenoxy)acetic acid] reduced wheat yield 28, 21 and 24%, reduced kernels per spike 27, 33 and 21%, and increased seed protein 8, 10 and 13%, respectively, when applied at Zadoks Stage 44 (mid‐boot). Several other auxin herbicides increased seed protein content, particularly when applied at Zadoks Stage 44. Proline and lysine content were not influenced by herbicide treatment at any stage of application. Spring wheat tolerance to bromoxynil (3,5‐dibromo‐4‐hydroxybenzonitrile), chlorsulfuron (2‐chloro‐Ar‐[[4‐methoxy‐6‐methyl‐l,3,5‐triazin‐2‐yl)amino]carbonyl] benzenesulfonamide} and MCPA was excellent regardless of growth stage at application.