Residual Herbicides for Weed Control in Established Alfalfa (Medicago sativa) Grown for Seed

Abstract

The long-term effect of repeated late-fall versus early-spring imazethapyr, hexazinone, terbacil, metribuzin, dichlobenil, or chlorsulfuron treatments, when applied on dormant stands of alfalfa was investigated at three sites for weed management of alfalfa grown for seed. Dichlobenil applied at 1.2 to 2.4 kg ha−1and chlorsulfuron applied at 11 to 22 g ha−1in fall or spring were the only herbicides to injure alfalfa at one location. Hexazinone provided the most consistent weed control of the herbicides evaluated. Average control of Canada thistle, catchweed bedstraw, dandelion, perennial sowthistle, quackgrass, Russian pigweed, and scentless chamomile was 80%. When averaged over three sites, weed control by hexazinone resulted in a 33% increase in seed yield.

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

“…Imazethapyr at the recommended rate of 1.0 l*ha -1 excellent controlled many predominant broadleaf species, except Cirsium arvense (78.5%), and showed insignificantly lower control of grass weeds in all experimental years (Table 4). Similar results were reported by Malik et al (1993), who stated that imazethapyr at rate of 0.2 kg a.i. *ha -1 excellent control Taraxacum officinale in established alfalfa stand, but control of Cirsium arvense was not satisfactory.…”

“…No evident alfalfa injury was detected in herbicide-treated plots with pronamide, prodiamine + metribuzin, and metribuzin at 0.3 kg*ha -1 (Wilson, 1989). Similar, no visual injury was recorded in established alfalfa when imazethapyr was applied on dormant stands of alfalfa (Malik et al, 1993). Opposite, metribuzin caused crop injury of alfalfa as a result of increased rate from 1.1 to 1.7 kg*ha -1 (Wilson, 1997).…”

“…Results from several experiments have shown that many herbicides can be used to control weeds selectively in established alfalfa (Wilson, 1981;Cosgrove and Barrett, 1987;Wilson, 1989;Malik et al, 1993;Wilson, 1997;Ashigh et al, 2009). 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).…”

Evaluating Glyphosate Treatments on Roundup Ready Alfalfa for Crop Injury and Feed Quality

“…Forage quality is usually highest in weed‐free stands (7,11,15). Once alfalfa is established, other herbicides may be used, such as paraquat applied to dormant alfalfa and between cuttings (6,9), imazethapyr or a postemergent grass herbicide (2,13), or residual herbicides such as pronamide and metribuzin, depending on the production system used (8,12). Glyphosate is labeled for application to dormant alfalfa stands that are not glyphosate tolerant.…”

Avaliação de resíduo do herbicida imazethapyr e da interferência de plantas daninhas na cultura da alfafa

“…Um dos problemas para o estabelecimento das plantas de alfafa no campo, tem sido a fitoxicidade dos herbicidas aplicados em pré ou em pós-emergência (Hasting & Kust, 1970;Kust, 1969;Oliveira et al,1997), mas foi observado que imazethapyr, aplicado nas doses de 0,1 e 0,2 kg/ha, não causou efeito fitotóxico na alfafa (Malik et al, 1993). Da mesma forma, Wilson, (1994), constatou que o imazethapyr não reduziu a produção de matéria seca da alfafa no primeiro corte e diminuiu acentuadamente a biomassa das plantas daninhas.…”