Broadleaf control

Hertz, L.B. and D.K. Wildung (1978). Quackgrass and broadleaf control in low-statured hybrid blueberries. HortScience, 13 699-700. Hogue, E.J. and G.H. Neilsen (1987). Orchard floor vegetation management. Hortic. Rev., 9 211-420. 

Annual bluegrass has shown susceptibility to currently available preemergence herbicides such as oryzalin, pendimethalin, dithiopyr, prodiamine, or oxadiazon (Smith et al., 1986 Webster et al., 1986 Higgins et al., 1991 Lewis, 1991 McCarty, 1991 Coats, 1992 Lewis, 1994 Murphy and Johnson, 1995). However, these herbicides do not provide broadleaf control equal to the triazines. Although annual bluegrass control is often very good with these herbicides, there are usually some broadleaf weeds that are not controlled, such as lawn burweed and purple cudweed (Murphy and Johnson, 1995). 

Typically, the inclusion of atrazine in an herbicide program results in good-to-excellent control of broadleaf and grass weed species. In a summary of 750 Midwest research trials conducted from 1972 through 1991, control efficacy was 80-100% in 74% of the broadleaf weed control trials in which atrazine was used (Pike et al., 1994). When atrazine was not used and other herbicides were used, broadleaf control in the 80-100% range was obtained only 54% of the time. 

Uses Atrazine is a symmetrical triazine used for broadleaf control on com. It forms major metabolite(s) by dealkylation of the ethyl or isopropyl side chains. Approximately 120 million pounds of triazines are used in the United States alone on com-growing fields. 

Table III. Postemergent Broadleaf Control in Greenhouse Tests...

Compound Number % Broadleaf Control (1) Rate (lb/acre)... 

Phenoxyalkanoics. The phenoxyalkanoic herbicide grouping is composed of two subgroups, the phenoxyacetic acids and the phenoxypropionic acids. The phenoxyacetic acid herbicides include some of the first commercially successhil herbicides, eg, 2,4-D. They continue to be widely used for foUar control of broadleaf weeds. The more heavily functionalized phenoxypropionic acid herbicides are relatively new herbicides compared to the phenoxyacetic acids and are used primarily for selective control of grassy weeds in broadleaf crops (2,296,297). 

Chloroacetanilides are soil-applied herbicides used for pre- and early post-emergence control of annual grasses and broadleaf weeds in crops. Representative chloroacetanilide compounds, alachlor, acetochlor, and metolachlor, are extensively used worldwide. Other chloroacetanilides with limited usages include propachlor, bu-tachlor, metazachlor, pretilachlor, and thenylchlor. Public environmental concerns and government regulatory requirements continue to prompt the need for reliable methods to determine residues of these herbicides. There now exist a variety of analytical methods to determine residues of these compounds in crops, animal products, soil, and water. The chemical structures and major crops in which these compounds are used are summarized in Table 1. 

Pyraflufen-ethyl was primarily developed as a cereal herbicide to control a broad spectrum of broadleaf weeds. Pyraflufen-ethyl applied in early postemergence at 12 g a.i. ha provides excellent control of some important weeds such as Anthemis arvensis, Lamium purpureum and Sinapis arvensis and good suppression of Matricaria chamomilla, Stel-iaria media, Veronica persica and Viola spp. 

Sulfentrazone is a broad-spectrum, pre-emergent herbicide that provides good control over broadleaf weeds, grasses and sedges in crops and turf. The metabolism of sulfentrazone in animals and plants is similar. The major plant metabolite of sulfentrazone is 3-hydroxymethyl sulfentrazone (HMS). The soybean tolerance of 0.05 mg kg includes residues of sulfentrazone plus its major metabolite, HMS. The rotational crop tolerance includes residues of sulfentrazone and its major metabolites, HMS and... 

Study 2. The effects of wheat, oats, barley and rye mulches on three broadleaf weed species and crabgrass (Digitaria spp.) are shown in Table VI. Weed control data for the corn test at Kinston are not presented because of poor cover crop kill by the paraquat treatment. 

Crabgrass control in the mulched plots was generally lower than the control of broadleaf species, despite the alachlor treatment at planting time (Table VI). Poor crabgrass control in the non-tilled treatments may have been due to the low early season rainfall which reduced the effectiveness of alachlor. 

Table VII. Mean broadleaf weed control of mulched and unmulched treatments averaged over location, crop, and weed species...

Atrazine is a white crystalline substance that is sold under a variety of trade names for use primarily as a selective herbicide to control broadleaf and grassy weeds in com and sorghum... 

Control of broadleaf weeds with 2,4-D has posed a new problem, the invasion of fields by true grasses, which will need specific herbicides. 

Molinate (S-ethyl hexahydro-azepine-l-carbothioate) has been widely used for broadleaf and grass weed control in rice culture. The 96-hour LC50 of technical molinate in the common goldfish is 30 ppm (1) and the medium tolerance limits (LTm) for molinate in mosquito fish (Gambusia affinis) are 16.4 ppm for 96 hours (J2). Kawatsu (3) estimated the 20-day lethal concentration of molinate in Japanese carp (Cyprinus carpio) var. Yamato koi at 0.18 ppm. However, there was no toxic effect of molinate on American carp at concentrations of 10 ppm during a two-week observation (40. ... 

Dicamba (3,6-dichloro-2-methoxybenzoic acid) is primarily used as a postemergence broadleaf herbicide, which interferes with normal plant auxin function, subsequently causing uncontrolled growth and the inhibition of the phototropic and geotropic function. Cumulative response results in plant death. The success of auxinic analogues such as Dicamba and 2,4-dichloropheno-xyacetic acid in weed control has led to widespread manufacturing and use. Estimated U.S. production for Dicamba was 5 million kg in 1990 [391]. 

This application was made between 0700 and 0830 a.m. in cool (air temp., 10 0 clear and windless weather. Both granular and emulsion formulations were incorporated to the 7.5cm depth with a disc cultivator within 15 minutes of application. A second cultivation to the same depth, but at right angles to the first, was completed within 2-3 hours. On May 20th both plots were spring-tooth harrowed for seed-bed preparation for soybean planting on the same day. The only subsequent soil disturbance was a row cultivation in late June to control a severe infestation of quack-grass control of broadleaf weeds was essentially complete with the trifluralin. 

Uses Pre-emergence herbicide used in soil to control germinating broadleaf grasses and weeds in crops such as apples, cotton, grapes, pears, pineapples, and alfalfa sugar cane flowering depressant. 

Bentazone Acid 25057-89-0 2.55 1972 Herbicide A postemergence herbicide used for selective control of broadleaf weeds and sedges (a weed) in beans, rice, com, peanuts, mint, and others... 

Rapid growth of chemical weed control did not occur until after World War II when a herbicide was introduced by Jones in 1945 at the Imperial Chemical Industries of England 2,4-dichlorophenoxyacetic acid (2,4-D). Its utility has come from its ability to kill selectively broadleaf weeds in cereal grains, com, and cotton. It does not disturb the soil and is not persistent. 2,4,5-T was launched commercially by American Chemical Paint Co. in 1948 (now Union Carbide) to combat brush and weeds in forests, along highways and railroad tracks, in pastures, and on rice, wheat, and sugarcane. 

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