Imazamox Rates, Timings, and Adjuvants Affect Imidazolinone-Tolerant Winter Wheat Cultivars

Abstract

Irrigated field experiments were conducted near Torrington, WY, during the 2001 to 2002 (year 1) and 2002 to 2003 (year 2) winter wheat growing seasons to evaluate cultivar response to different imazamox rates, adjuvants, and application timings. Five cultivars were treated postemergence in the early fall (EF), late fall (LF), or early spring (ES) with imazamox at 54 or 108 g ai/ha, including either nonionic surfactant (NIS) at 0.25% or methylated seed oil (MSO) at 1% (v/v) as adjuvants. A 28% urea ammonium nitrate solution at 1% (v/v) was included with all treatments. Spring injury was more severe in year 1 than year 2. Severe spring injury on ‘AP502 CL’, ‘Above’, ‘IMI-Fidel’, ‘IMI-Jagger’, and ‘IMI-Madsen’ was linked to fall application of 108 g/ha imazamox with MSO. Imazamox applied at 108 g/ha plus MSO applied in the fall consistently injured all cultivars more than the same rate with NIS and 54 g/ha imazamox regardless of adjuvant and timing, although severity of injury in the experiments differed between EF and LF timings in years 1 and 2, respectively. Correlation analysis supports injury reduced reproductive tillers per meter of row and wheat yields and increased the number of seeds per spike in year 1. The reduction of reproductive tillers per meter of row in year 1 was likely the result of severe injury caused by 108 g/ha imazamox applied in the EF coupled with little snow cover to protect against cold winter temperatures. Wheat yield in year 1 was reduced by 108 g/ha imazamox applied in the early fall; however, imazamox applied at 54 g/ha with either adjuvant in EF, LF, or ES were safe. Yield parameters and wheat yields in year 2 were not affected by imazamox rate, adjuvant, timing, or interactions of these factors.

Response of Selected Hard Red Wheat Lines to Imazamox as Affected by Number and Location of Resistance Genes, Parental Background, and Growth Habit

“…Wheat injury consists of minor chlorosis, dark green color of developed leaves, or stunting and yield loss can occur (Pozniak et al, 2004b). Crop injury can be influenced by application parameters such as high imazamox rates, surfactants, and application timing (Frihauf et al, 2005;Geier et al, 2004;Stougaard et al, 2004). Anecdotal evidence also suggests that environmental stresses during or immediately following imazamox application may influence injury (M. Dahmer, personal communication).…”

Increased Foliar Activity of Isoproturon+Tribenuron and Pyroxsulam Against Little Seed Canary Grass and Field Bindweed by Proper Adjuvant Selection in Wheat

“…Adjuvants improve the efficacy of post-emergence herbicides at reduced doses and give efficient weed control (Green and Foy, 2000;Johnson et al, 2002). Herbicide use can be reduced by 75% through the integration with adjuvants without compromising yield and net benefits for the cost-effective and eco-friendly management of weeds (Frihauf et al, 2005). Herbicides are now trending towards more active and concentrated formulations used at reduced doses.…”

Herbicides and Adjuvants

“…The interactions between herbicide adjuvants and herbicide activity, however, are not simple processes, and depend on factors that include crop/weed leaf surface, droplet characteristics, adjuvant type, chemical form of the herbicide, and environmental conditions. Understanding the complexity of these interactions is essential for optimum herbicide utilization, particularly in prolonging, enhancing and improving the efficacy; reduction of the critical rain-free period; minimizing herbicide leaching into groundwater; and decreasing harmful effects to non-target plants and animals.• Decreasing the activity of the herbicide (antagonistic effects) [33] • Increasing the formulation's ability to spread or persist in the environment where it is not wanted [34,35], or otherwise• Increasing harmful effects to non-target plants [36,37] and aquatic species [38,39] Herbicides, Physiology of Action, and Safety 126 Herbicides and Adjuvants http://dx.…”

“…• Increasing harmful effects to non-target plants [36,37] and aquatic species [38,39] Herbicides, Physiology of Action, and Safety 126 Herbicides and Adjuvants http://dx.…”