Selective Control of Downy Brome in Alfalfa

Abstract

Selective control of downy brome (Bromus tectorumL.) in alfalfa (Medicago sativaL.) was studied in 1971 and 1972. Herbicidal efficacy and alfalfa tolerance, yield, and percent and total protein were observed. The weed population was composed of almost 100% downy brome in 1971 and 1972. Herbicide treatments were applied early and late winter when both alfalfa and downy brome were dormant. Five herbicides afforded virtually complete downy brome control in 1971: pronamide [3,5-dichloro-N-(1,1-dimethyl-2-propynyl) benzamide] at 0.84 and 1.40 kg/ha, simazine [2-chloro-4,6-bis(ethylamino)-s-triazine] at 1.12 kg/ha, terbacil (3-tert-butyl-5-chloro-6-methyluracil) at 0.84 kg/ha, paraquat (1–1′-dimethyl-4,4′-bipyridinium ion) at 0.56 kg/ha and cyanazine {2-[[4-chloro-6-(ethylamino)-s-triazin-2-yl] amino]-2-methylpropionitrile} at 3.4 kg/ha. All herbicide treatments reduced downy brome yields in 1972. Significantly higher alfalfa yields were closely related with lower downy brome yields. In 1972, alfalfa treated with propham (isopropyl carbanilate), cyanazine, pronamide and terbacil also was higher in second cutting yields than the control. Twelve of the 23 treatments, including all triazine herbicides, increased first harvest alfalfa protein percentage in 1972 although differences were not observed in 1971. Alachlor [2-chloro-2′,6′-diethyl-N-(methoxymethyl)-acetanilide] spring-applied in 1971 at 5.62 kg/ha was the only treatment causing visual alfalfa injury.

Downy Brome (Bromus tectorum) Control in Established Alfalfa (Medicago sativa)

“…In some studies. weed control has increased alfalfa yields (Kapusta and Strieker 1975;Wilson 1981). while in others.…”

Low-Dose Glyphosate Does Not Control Annual Bromes in the Northern Great Plains

“…have severe implications for fire cycles in the Intermountain West, with millions of dollars in associated costs (DiTomaso 2000), but these exotic, invasive species have a different impact in the Great Plains. Downy brome in particular reduces the profitability of alfalfa fields (Kapusta and Strieker 1975), winter wheat croplands (Ostlie and Howatt 2013;Wicks 1984), and perennial grass pastures and seed production areas (Wicks 1984). In mixed-grass prairie rangelands, both downy brome (hereafter referred to as BROTE) and Japanese brome (or BROJA) competitively suppress native perennial grass species (Haferkamp et al 1997) and also reduce litter decomposition rates (Ogle et al 2003), negatively affecting the ecosystem services of stable biomass production and soil nutrient availability.…”

“…However, a fall application of glyphosate may not be sufficient for control of annual bromes due to the transient nature of glyphosate and spring-germinating cohorts. Others have shown that early-spring herbicide application is best for BROTE control (Wicks et al 1965), but the danger is that late-spring applications are generally ineffective (Kapusta and Strieker 1975) and "springtime" conditions can occur anytime between February (Kapusta and Strieker 1975) and May (Blackshaw 1991) in the northern plains and prairies. Even though theoretically a single spray event could extirpate populations of annual weeds, spraying in consecutive years to achieve control of annual bromes has been recommended (Owen et al 2011;Wicks et al 1965).…”

Co-transforming bar and CsALDH Genes Enhanced Resistance to Herbicide and Drought and Salt Stress in Transgenic Alfalfa (Medicago sativa L.)

“…Moreover, alfalfa yield can be reduced through competition with weeds for growth conditions. Its forage quality can be lowered by decreasing the digestibility and protein content of hay brought about by moderate to severe weed infestation ( Cords, 1973 ; Kapusta and Strieker, 1975 ). Alfalfa yield from the first herbage cut can be reduced by 60–80% when volunteer monocots are not controlled in the fall.…”