Susceptibility of Alfalfa Cultivars to Triazine Herbicides¹

Abstract

While simazine [2‐chloro‐4,5‐bis(ethylamine)‐s‐triazine] has been used for several years to control perennial broadleaf weeds in alfalfa (Medicago sativa L.), it occasionally fails to provide adequate weed control, or causes crop injury. Other triazine herbicides have been shown to provide more reliable weed control but also may injure the crop. Consequently, this study was conducted to determine which triazine herbicide was least injurious to alfalfa and if alfalfa cultivars differed in their susceptibilities to the herbicides. Included in the study were five alfalfa cultivars and the herbicides atrazine [2‐chloro‐4‐(ethylamino)‐6‐(isopropylamino)‐s‐triazine], cyanazine [2‐chloro‐4‐ (1‐cyano‐1‐methylethylamino)‐6‐ethylamino‐s‐triazine], secbumeton (2‐sec‐butylamino‐4‐ethylamino‐6‐methxy‐s‐triazine) and simazine. The cultivars were established on silt loam (Typic Argin‐doll Fine‐Silty Mixed Mesic) and loamy sand (Typic Udipsament Sandy‐Mixed) soils. Results of tests conducted on both soils indicated that the ‘Vernal,’ ‘Saranac,’ and ‘Iroquois’ cultivars had the greatest yield potential under Wisconsin conditions, but when expressed as a percentage of yield in untreated plots, the ‘Tempo’ cultivar was injured least by the herbicides. The ‘DuPuits’ cultivar, while initially responding to the triazine herbicides much like the other cultivars, exhibited greater injury after overwintering. Initial injury to the Vernal cultivar on the silt loam soil was greatest from atrazine, secbumeton, and cyanazine, but recovery was nearly complete by the spring following treatment. On the loamy sand soil, however, atrazine and high rates of simazine produced the greatest initial injury, and injury to the Vernal cultivar persisted through the following spring.

Weed control in dormant alfalfa (Medicago sativa L.) with active ingredients� metribuzin, imazetapyr and pronamide

“…Herbicides such as imazetapyr, metribuzin and pronamide generally are applied during alfalfa dormant period (November -February) to control weeds effectively, and, in same time, to avoid alfalfa crop injury (Waddington, 1980;Peters et al, 1984). As a result of that, yield and quality of established alfalfa increased (Harvey et al, 1976;Kapusta and Stricker, 1975;Fawcett et al, 1978;Wilson, 1981).…”

New Herbicides for Weed Control in Established Alfalfa (Medicago sativa)

“…If the weed when harvested is of lower quality than alfalfa, the quality of the forage declines as the percent age of weeds increases (2,3,7,9). In some studies, weed control has increased alfalfa yields (4,6,9); and in others, yields were similar or less following weed control (10,11). Results from several experiments have shown that herbicides can be used to control weeds selectively in established alfalfa (4,5,6,8,11).…”

Effect of soil temperature, seeding depth and cultivar on wheat tolerance to simulated ethalfluralin carryover

“…Clay et al (1995), Heath (1981) and Olson and McKercher (1985) have observed differences in tolerance of wheat cultivars to trifluralin. Harvey and Gritton (1977) also observed differences in tolerance to trifluralin among pea cultivars. However, Darwent et al (1990) found no differences in tolerance to trifluralin among barley cultivars.…”