2,4-DB

Abstract: Alfalfa and sainfoin were sown in 1978, 1979, and 1980 on irrigated land at the Lethbridge Research Station. The forages were established using herbicides for weed control, no weed control, or a barley companion crop. Weed control treatments were applied only during the establishment year (year 1). Alfalfa yields, averaged from the three seedings, were 360 and 200 g/m2 greater during year 1 and year 2, respectively, when diclofop plus 2,4-DB was applied than when the companion crop was grown and no weed control was used. Weed yields were greater in years 2 and 3 where alfalfa was established in competition with weeds or companion crops than where weeds were controlled. Alfalfa yields were similar for all treatments in years 3 and 4. Year 1 treatments in sainfoin produced yield differences similar to those described for alfalfa; however, sainfoin yields tended to be smaller and weed yields larger. Year 1 and year 2 forages with high weed contents have acceptable nutrient composition but may not be saleable...

Abstract: Weed management during alfalfa (Medicago sativa L.) establishment is a major concern for producers in the northeast USA. The objectives of this research were to determine the yield, quality, and economic consequences of controlling weeds during the establishment of spring- and summer-seeded alfalfa. Alfalfa was band-seeded during spring (April and May) and late summer (August and September) into a conventionally tilled seedbed of Hagerstown silt loam (fine-loamy, mixed, mesic Typic Hapludalfs) at Landisville, PA, in 1991 and Murrill silt loam (fine-loamy, mixed, mesic Typic Hapludult) at Rock Springs, PA, in 1991 and 1992. Weed control treatments for the spring seedings included: (i) no herbicide or nurse crop (no weed control); (ii) oat (Avena sativa L.) nurse crop; (iii) benefin preplant incorporated; and (iv) sethoxydim and 2,4-DB postemergence. Weed control treatments for late-summer seedings were the same as those in the spring except that the nurse crop was replaced with a paraquat application to dormant alfalfa. Seeding alfalfa later, compared with earlier, in the spring tended to increase weed and decrease alfalfa dry matter (DM) yield but did not affect total DM yield or forage quality during the seeding year. For spring-seeded alfalfa, weed control treatment effects on alfalfa and weed DM yield during the seeding-year were sporadic, however, net economic return per acre was generally greatest when no weed control was used. Neither time of spring seeding nor weed control treatments produced consistent differences in yield, quality, or net economic return per acre after the seeding year. Delaying alfalfa seeding in the summer reduced first harvest alfalfa yield (704 Ib/acre less) and season total alfalfa yield (1121 Ib/acre less) compared with early seedings. Generally, weed control treatments in summer-seeded alfalfa did not improve alfalfa or total DM yield, forage quality, or net economic return per acre compared with no weed control. We conclude that when alfalfa is either spring or summer seeded, the weed control practices used in this study were not economically beneficial and may actually reduce net return per acre because of associated additional costs compared with seeding alfalfa with no companion crop or herbicide.

Abstract: Control of Texas panicum and southern crabgrass with sethoxydim was reduced under field conditions when bentazon, acifluorfen, bentazon + acifluorfen, pyridate, or naptalam plus 2,4-DB was added. The addition of lactofen to sethoxydim did not result in antagonism. Complete control of annual grasses did not appear to be a necessity in order to improve peanut yields. Peanut yields in plots with 70 to 80% control of annual grasses were comparable to those where annual grass control was 99%. Nomenclature: Acifluorfen, 5-[2-chloro-4-(trifluoromethyl)phenoxy]2-nitrobenzoic acid; bentazon, 3-(l-methylethyl)-(lH)-2,1,3-benzothiadiazin-4(3H)-one 2,2-dioxide; 2,4-DB, 4-(2,4-dichlorophenoxy)butanoic acid; lactofen, (?)-2-ethoxyl-methyl-2-oxoethyl 5-[2chloro-4(trifluoromethyl)phenoxy] -2-nitrobenzoate; naptalam, 2[(1 -naphthalenylamino)carbonyl]benzoic acid; pyridate, 0-(6-chloro-3-phenyl4-pyridazinyl S-octyl carbonothioate; sethoxydim, 2-[l-(ethoxyimino)butyl]-5-[2-(ethylthio)propyl]-3-hydroxy-2-cyclohexen-l-one; peanut, Arachis hypogaea L. 'Florunner'; southern crabgrass, Digitaria ciliaris (Retz.) Koel. #3 DIGSP; Texas panicum, Panicum texanum Buckl. # PANTE. Additional index words: Antagonism, tank-mixes, acifluorfen, bentazon, 2,4-DB, lactofen, pyridate, naptalam, southern crabgrass, Texas panicum.

Abstract: Postemergence herbicide treatments that were most effective for controlling horsenettle (Solarium carolinense L.) were glyphosate [N-(phosphonomethyl)glycine], dicamba (3,6-dichloro-o-anisic acid), silvex [2-(2,4,5-trichlorophenoxy)-propionic acid], and picloram (4-amino-3,5,6-trichloropicolinic acid). All exhibited good to excellent long term control of the horsenettle plant when applied annually for at least 2 yr. Picloram and glyphosate both provided better control of horsenettle when applied at a postbloom or fruiting stage of growth. Dicamba and picloram also were very effective in controlling horsenettle when used as a subsurface layer (SSL) treatment. However, all of these treatments caused visual injury to peanuts (Arachis hypogaea L.). Applications of 2,4-DB [4-(2,4-dichorophenoxy)butyric acid] were effective in causing an 80 to 90% fruiting inhibition of horsenettle plants when applied at a prebloom stage of growth, with no damage to the peanuts. Applications of several dinitroaniline herbicides as SSL treatments exhibited some control of horsenettle with little crop injury. Postemergence treatments which effectively controlled seedling horsenettle plants grown in the greenhouse were glyphosate and dinoseb (2-sec-butyl-4,6-dinitrophenol).