Reduced abundance at 20 ug/L (Dewey 1986) Shift in emergence period at 20 ug/L (Dewey 1986) Reduced emergence at 20 ug/L (Dewey 1986) 1979)Ĭontinuous exposure across generations produced reproductive effects on the third generation including rapid embryonic development, embryonic abnormalities and increased egg laying (Tate et al. More sensitive response to Roundup® at elevated temperatures and at pH as it rises from 6.5 to 7.5, with no increased sensitivity at pH beyond 7.5 (Folmar et al. 1979)Īcute 96h LC 50 is 97mg/L technical glyphosate and 1.0 mg/L Roundup® surfactant (Folmar et al. 1979)Īcute 96h LC 50 is 130mg/L technical glyphosate and 13mg/L Roundup® surfactant (Folmar et al. 1979)Īvoided Roundup® at 10 mg/L but not 1.0 mg/L (Folmar et al. Examples of Herbicide Concentrations Causing Toxic Effects HerbicideĪcute 48h EC 50 is 55 mg/L technical glyphosate and 13mg/L Roundup® surfactant (Folmar et al. Acute toxicity is likely only when they are deliberately or accidentally applied directly to water bodies. Most commonly, they enter surface water in runoff or leachate, but, because they have relatively low toxicity to fish and invertebrates (see Table 2). Herbicides may cause biological impairments of water bodies if they occur in water or sediment at sufficient concentrations. This herbicide is applied to the soil to control target vegetation by inhibiting or disrupting cell division in shoots.Īdapted from Ross and Childs (1996) and USDA commercial names in italics. These herbicides are applied to the soil to control target vegetation before emergence by inhibiting root growth.Īpplied pre-planting to control annual grasses and broadleaf weeds among crops such as corn and soybeans. They are fast acting: effects on foliage are visible within minutes of application.Īpplied to control grasses and broadleaf weeds in crops such as beans, peanuts, cotton and tobacco. Effects can be observed as discoloration of foliage and deformations in new growth. These synthetic growth hormones are applied to the foliage of dicots and transported to meristems causing uncontrolled growth. Also applied for control of broad-leafed trees when planting conifers. Urban use on lawns and grassy rights of way. They inhibit photosynthesis.Īpplied to broad-leafed weeds in corn, small grains, sorghum, pastures and rangeland. These broad spectrum herbicides are applied at the soil and carried to the leaves by transpiration. Effects will manifest in two or more weeks as discoloration of foliage and deformations in new growth.Īpplied to control weeds in alfalfa, barley, soybeans and wheat.Īpplied to control weeds in small grains, soybeans and corn and in conifer and hardwood plantations.Īpplied to crops such as corn, soybeans and sorghum, particularly for conservation tillage. Because of its broad spectrum and relatively low toxicity to animals, it is used in horticulture and in the control of aquatic macrophytes.Īpplied to the foliage and transported with sugars to metabolic sites where they inhibit amino acid production. Roundup, Ultra, Rodeo, TouchDown Pro, AccordĪpplied primarily to genetically engineered, glyphosate-resistant varieties of soybeans, corn, canola and cotton. Common Applications and Modes of Action of the Ten Most Heavily Used Herbicides in the United States, 2001 Herbicide Glyphosate and atrazine were applied to more than double the crop field acreage than the third leading herbicide, 2,4-D, in 2001. Application methods include spraying onto foliage, applying to soils and applying directly to aquatic systems.įigure 1 and Table 1 present the ten herbicides most used on agricultural land in the U.S. Herbicides can act by inhibiting cell division, photosynthesis or amino acid production or by mimicking natural plant growth hormones, causing deformities (Ross and Childs 1996). The molecular site of action is challenging to predict because structural associations have not been identified (Duke 1990), but modes of action are well-established. The potential effects of herbicides are strongly influenced by their toxic mode of action and their method of application. These weeds can impede irrigation withdrawals or interfere with recreational and industrial uses of water (Folmar et al. Herbicides are applied to water bodies to control aquatic weeds. In suburban and urban areas, herbicides are applied to lawns, parks, golf courses and other areas. The total applied volume and area covered is greater but the frequency of application is much less than for farming (Shepard et al. Herbicides are used in forest management to prepare logged areas for replanting. Reproduced from USDA Economic Research Service, Pest Management
Agricultural use of herbicides in 2001 in millions of acres.
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