- general description
- When to make a list
- to measure ways
- concept diagrams
- literary criticism
- references
general description
- Sources, site evidence and biological impact checklist
- Other stressors that can affect the action of herbicides
Herbicides are chemicals used to manipulate or control unwanted vegetation. Application of herbicides is most common in row crops, where they are applied before or during planting to maximize crop productivity by minimizing other vegetation. They can also be applied to crops in the fall to enhance harvest.
Herbicides are used in forestry to prepare cleared land for replanting. The total amount applied and the area covered are higher, but the frequency of application is much lower than in agriculture (Shepard et al. 2004).
In suburban and urban areas, herbicides are applied to lawns, parks, golf courses, and other areas. Herbicides are applied to bodies of water to control aquatic weeds. These weeds can prevent irrigation abstraction or affect recreational and industrial uses of water (Folmar et al. 1979).
The possible effects of herbicides are strongly influenced by their toxic mode of action and their mode of application. The molecular site of action is difficult to predict as no structural associations have been identified (Duke 1990), but the modes of action are well established.
Herbicides can act by inhibiting cell division, photosynthesis or amino acid production, or by mimicking natural plant growth hormones and causing birth defects (Ross and Childs 1996). Methods of application include foliar spraying, soil application and direct application to aquatic systems.
Figure 1 and Table 1 represent the top ten herbicides used on farmland in the United States. In 2001, glyphosate and atrazine were applied to more than twice the area of the third most important herbicide, 2,4-D.
| Herbicide | Common application | action mode |
|---|---|---|
| Amino Acid Inhibitors | ||
| glyphosate Summary, Ultra, Rodeo, TouchDown Pro, Accord | It applies in particular to glyphosate-resistant genetically modified soybean, maize, canola and cotton varieties. It is also used to control shrubs. Due to its broad spectrum of activity and relatively low toxicity to animals, it is used in horticulture and to combat aquatic macrophytes. | Applied to leaves and carried with sugars to metabolic sites where they inhibit amino acid production. The effects manifest themselves in two or more weeks as discoloration of foliage and deformation of new growth. |
| imazetapir Seek | Used to control weeds in alfalfa, barley, soybeans and wheat. | |
| Thifensulfuron Lighthouse, Summit, Harmony | Used to control weeds in small grains, soybeans and corn, and in coniferous and hardwood plantations. | |
| Photosynthesehemmer | ||
| discovered Atrex, Atrazina | It is applied to crops such as corn, soybeans and sorghum, especially for conservation tillage. | These broad spectrum herbicides are applied to the soil and transported to the leaves by transpiration. They inhibit photosynthesis. |
| Cyanazine Bladex/Dupont | ||
| Synthetic auxin, growth regulators | ||
| 2,4-D | It is applied to broadleaf weeds in corn, small grains, sorghum, grasses and willow. Urban use on lawns and grassy paths. It is also used to control deciduous trees when planting conifers. | These synthetic growth hormones are applied to the leaves of dicots and transported to the meristems, causing uncontrolled growth. The effects can be seen as discoloration of foliage and distortions in new growth. They act quickly: the effect on the leaves is visible within a few minutes after application. |
| dicamba Banvel, Clarity, Conquest, Veteran | ||
| cell division inhibitors | ||
| Trifluralina treflan and others | It is used to control grasses and broadleaf weeds in crops such as beans, peanuts, cotton and tobacco. | These herbicides are applied to the soil to control target vegetation before it emerges by inhibiting root growth. |
| Pendimethalin Prowl, Pentagon, Pendulum, Stomp | ||
| Metolachlor Doble, Doble Magnum, Wimpel Magnum | It is applied before planting to control annual grasses and broadleaf weeds on crops such as corn and soybeans. | This herbicide is applied to the soil to control target vegetation by inhibiting or disrupting cell division in shoots. |
| Adapted from Ross and Childs (1996) and USDA; Trade names in italics. | ||
Herbicides can cause biological damage in aquatic environments when present in sufficient concentrations in the water or sediment. They typically enter surface waters as runoff or leaching, but because they have relatively low toxicity to fish and invertebrates (see Table 2). Acute toxicity is only likely when applied directly to the aquatic environment, intentionally or accidentally.
| Herbicide | Taxa | biological effect |
|---|---|---|
| glyphosate | ||
| water flea Big water flea | Acute 48 h EC50es 218 mg/L (ECOTOX) | |
| Amphipode Gammarus pseudolimnaeus | Acute 48 h EC50es 42-62 mg/L (ECOTOX) | |
| buzzing mosquito Chironomus plumosus | Acute 48 h EC50is 55 mg/l technical glyphosate and 13 mg/l Roundup® surfactant (Folmar et al. 1979) | |
| mayfly newspaper runner | Evite Roundup® a 10 mg/L oder nein a 1,0 mg/L (Folmar et al. 1979) | |
| Welskanal spotted ichthalur | Akute LC 96h50is 130 mg/L technical glyphosate and 13 mg/L Roundup® surfactant (Folmar et al. 1979) | |
| Bighead Minnow Pimephales Promelas | Akute LC 96h50is 97 mg/l technical glyphosate and 1.0 mg/l Roundup® surfactant (Folmar et al. 1979) | |
| rainbow trout Oncorhynchus mykiss | More sensitive response to Roundup® at elevated temperatures and at pH increasing from 6.5 to 7.5, with no increase in sensitivity at pH above 7.5 (Folmar et al. 1979) | |
| bluegill Lepomis macrochiru | ||
| american ribbed snail Pseudosuccinia columela | Continued intergenerational exposure resulted in reproductive effects in the third generation, including rapid embryonic development, embryonic abnormalities and increased oviposition (Tate et al. 1997). | |
| discovered | ||
| Mosquito Labrudinia pilosella | Emission reduced to 20 ug/L (Dewey 1986) | |
| Microcaddisfly creme und braun Oxyethira pallida | Change in emergence time to 20 ug/L (Dewey 1986) | |
| non-predatory insects | Abundance reduced to 20 ug/L (Dewey 1986) | |
| The stone algae Charasp. | Resistant to atrazine up to 100 ug/L (Dewey 1986) | |
| Tigersalamander Ambystoma tigrinussp. | Longer duration of the larval stage, reduced body weight and body size (Larson et al. 1998) | |
| Hydrasp. | 48 Std. CL503000 ug/L (lowest acute value) (U.S. EPA 2003) | |
| goldfish carasio dorado | 96 Std. CL5060,000 ug/L (highest acute value) (US EPA 2003) | |
| water flea doubtful ceriodaphnia | Chronic life cycle value of 3536 ug/L (highest chronic value) (U.S. EPA 2003) | |
| Bachforelle Salvelinus fontinalis | Chronic life cycle value of 88.32 ug/L (lowest chronic value) (U.S.EPA 2003) | |
Direct applications can result in direct toxicity to non-target plants and animals, or indirect effects through plant death and spoilage. Deficiency symptoms are also more likely when herbicides are applied together or with other pesticides (Streibig et al. 1998), resulting in additive or synergistic effects.
Atrazine reacts synergistically with chlorpyrifos: the mixture was seven times more toxic to one worm species than either pesticide individually (Lydy and Linck 2003). Atrazine also potentiated the effects of other pesticides on mosquito larvae and various flies (Belden and Lydy 2000, Lydy and Linck 2003). Surfactants used in herbicide solutions can also be toxic to biota and are not taken into account when testing active substances (Folmar et al. 1979).
Sources, site evidence and biological impact checklist
Herbicides are addressed in this module as immediate stressors. Herbicides should be a possible cause when human sources and activities, site observations, or observed effects support parts of the causal pathways (see Figure 2). The conceptual diagram and other information may also be helpful in Step 3: Evaluating the Case Data.
Rather than causing direct toxicity to organisms, herbicides may contribute to other stressors (e.g., alteration of river habitat by deforestation of riparian forests). In such cases, herbicides can be considered part of the route to the proximate cause of the deterioration.
The checklist below will help you identify important facts and information to help you decide if herbicides are among your possible causes. This list is intended to assist you in gathering evidence to support, weaken, or eliminate herbicides as a potential cause.
For more information on specific entries, seeWhen to make a listEyelash.
sources and activities
- forest office
- Agriculture/crops
- Parks
- golf courses
- Lawn
- Roads/Rights of Way
- Control of aquatic weeds
website proof
- dead or injured plants
- kill parts
- irrigation canals
- Drainage of fields or lawns
- orchards
biological effects
- Inhibition of phytoplankton, periphyton or macrophytes
- Reduced richness and abundance of invertebrate species
- Reduction of sensitive species and abundance of tolerant species
Other stressors that can affect the action of herbicides
- Temperature: Elevated temperatures often tend to increase the toxicity of chemicals.
- medium to high pH: pH determines the ionic state and bioavailability of ionizable herbicides.
- Dissolved Oxygen (DO): Signs of herbicide use are evidence of a causal pathway to low DO when DO is a possible cause of death or other deterioration.
- Toxic not stated: Surfactants in herbicide formulations can be more toxic to animals than the active ingredients (Folmar et al. 1979, Diamond and Durkin 1997). The toxicity of Roundup®, which increased with increased pH, was attributed to the surfactant rather than the active ingredient glyphosate (Folmar et al. 1979). This finding is reinforced by the findings that more alkaline pH reduces glyphosate toxicity but increases surfactant toxicity (Diamond and Durkin 1997).
You may also want to consider other causes with similar evidence:
- insecticides
- endocrine disruptor
- toxic metals
When to make a list
- Sources and activities that suggest including herbicides as a possible cause
- Site evidence suggesting ingestion of herbicides as a possible cause
- Biological effects suggesting including herbicides as a possible cause
- Evidence from website supporting the exclusion of herbicides as a possible cause
Sources and activities that suggest including herbicides as a possible cause
Forest management practices, agricultural operations, and urban development and maintenance are all sources of herbicides that can enter surface water and cause damage. Herbicides are applied to forests after harvest to suppress undergrowth and non-commercial trees. For this use, the application rate can be high, and exposed streams are more likely to be of better quality than agricultural or urban streams. In contrast, farms can contribute large amounts of herbicides because they can apply herbicides several times a year and by plane in addition to irrigating water or spraying crops (see Figure 3).
Urban land uses can contribute, as owners and managers of parks, golf courses, and other lawns use herbicides to improve aesthetics. Herbicides are also used on highway, pipeline, railroad and high-voltage line rights of way and to control plants in pavement cracks. Such urban and suburban uses can pollute storm water.
Herbicides are also applied directly to water to control vegetation in ponds, ditches, irrigation canals, and recreational water bodies. Such uses are sources of exposure at the point of use and downstream.
Site evidence suggesting ingestion of herbicides as a possible cause
Although herbicides are generally less toxic to animals than other pesticides, the death of fish or invertebrates can be a sign of herbicide use. For example, acrolein has been applied in irrigation ditches in amounts sufficient to be extremely lethal to fish and invertebrates (see U.S. EPA 2009 for acrolein), and if improperly applied to fields, it can cause death in receiving waters. . Fatalities can also result from low levels of dissolved oxygen (DO) resulting from the decomposition of plant matter in the water.
Biological effects suggesting including herbicides as a possible cause
Because herbicides tend to affect plants faster and more severely than animals, the most useful biological marker of herbicides is the effect on aquatic plants (Kreutzweiser et al. 1995, Van den Brink et al. 1997, Hall et al. 1997). This feature can help distinguish the biological effects of herbicides from those of insecticides and most other toxic chemicals. Secondary effects of herbicides are mediated by low DO concentrations from plant decay and changes in trophic structure due to changes in the plant community.
Herbicides can reduce the taxonomic richness and abundance of benthic fish and macroinvertebrates due to a reduction in vulnerable species and an increase in the abundance of tolerant species at high concentrations (Daam and Van den Brink 2007, Dewey 1986). Some herbicides, notably atrazine, have also been attributed specific mechanisms of action in frogs and aquatic fish, including developmental disorders (Hayes et al. 2006, Tillit et al. 2010). However, a review by the US EPA found that the evidence for such effects in amphibians is weak and conflicting (US EPA 2007).
Evidence from website supporting the exclusion of herbicides as a possible cause
to measure ways
Herbicides and their metabolites can be measured in ground and surface water using gas chromatography (GC), mass spectrometry (MS), high performance liquid chromatography with diode array detection (HPLC/DAD), liquid chromatography (LC), solid phase extraction (SPE) or enzyme-linked Immunosorbent Assay (ELISA) (Scribner et al. 2000). Since there is no standard method for detecting all herbicides, measurements can be difficult, expensive and time consuming.
Herbicide metabolites can have similar toxicity to the parent herbicide and are often found at higher concentrations (USGS 2010). Currently, metabolites of triazines, chloroacetanilides, phenylureas and phosphanoglycine glyphosate have been measured (Scribner et al. 2000, USGS 2010). Different herbicides and metabolites can be measured using different techniques, and the correct technique must be adapted to the metabolite of interest. The USGS Toxic Substances Hydrology Program provides guidance, laboratory methods, field methods, and literature for detecting herbicides in ground and surface water.
concept diagrams
- About concept diagrams
- Simple conceptual mockup diagram
- Detailed diagram of the conceptual model
About concept diagrams
Conceptual diagrams are used to describe hypothetical relationships between sources, stressors, and biotic responses within aquatic systems.
- More about concept diagrams
Simple conceptual mockup diagram
Herbicides are used to control unwanted plants on farms, commercial forests, and managed lawns and landscapes. Herbicides are sometimes applied directly to surface water to control aquatic weeds. Herbicides are typically applied to soil or terrestrial vegetation, which can increase herbicide delivery to groundwater, atmospheric drift, and runoff. The extent to which herbicides reach running waters depends on factors such as rainfall, timing and application rate, and the persistence of the herbicides and their metabolites in the environment.
Downloads
- Simple and detailed conceptual model diagrams
- Diagram conceptually simple (PPT) (ppt) (138.5 KiB)
- Detailed concept diagram (PPT) (ppt) (185 KB)
In rivers, herbicides can dissolve in the water column or bind to sediments, and their effect depends on the environment in which they are produced. Exposures can be episodic (e.g., during runoff events) or continuous (e.g., exposure to bottom sediments contaminated with herbicides). The bioavailability, absorption and toxicity of herbicides vary with environmental conditions (e.g. pH).
Elevated levels of herbicides in streams can affect stream flora and fauna through multiple mechanisms, including decreased growth, condition, and reproduction; increased mortality; and behavior changes. These effects can lead to biologically damaged aggregations of macrophytes, periphyton, phytoplankton, fish and invertebrates, which in turn can contribute to changes in community structure and ecosystem function.
Detailed diagram of the conceptual model
High concentrations of herbicides and their metabolites in streams can have lethal and sub-lethal effects on aquatic biota, potentially altering community structure and ecosystem function. This conceptual diagram (Figure 7) illustrates the links between human activities and sources (top of diagram), herbicide-related stressors (middle of diagram), and resulting biological responses (bottom of diagram).
In some cases, additional steps leading from sources to stressors, modes of action leading from stressors to responses, and other modifying factors are shown. This narrative generally follows the diagram from top to bottom and left to right.
Linking sources to stressors
Anthropogenic activities and land uses such as industry, urban development, forestry and agriculture can introduce herbicides into watercourses. Herbicide manufacturers, industrial plants and sewage treatment plants can discharge effluent containing herbicides. Accidental or unauthorized downloads can also occur.
Herbicides are sometimes applied directly to surface water for aquatic weed control (eg, aquatic recreation). Herbicides can be applied to golf courses, lawns and other managed landscapes, forests, crop fields, and orchards to control a variety of undesirable vegetation. In some cases herbicides can be transported atmospherically in spray drifts. These applied herbicides can enter streams through stormwater runoff, groundwater discharges, or direct atmospheric deposition.
Stored herbicides can also enter rivers through runoff or groundwater, both at the locations where they are used and at the locations where they are manufactured. The extent to which these transport routes occur depends on several factors, including soil cover, rainfall patterns, timing and application rates, and the persistence of the herbicides in the environment.
Linking stressors to biological responses
In rivers, herbicides can dissolve in the water column or bind to sediments, and their effect depends on the environment in which they are produced. Exposures can be episodic (eg, pulsed discharges with stormwater runoff) or continuous (eg, long-term exposure to herbicide-contaminated sediments). The bioavailability, absorption, and toxicity of herbicides and their metabolites during these exposures depend on factors such as temperature, pH, and dissolved oxygen concentrations.
The most direct effects of herbicide contamination are decreased condition, growth and reproduction, and increased mortality of plants (ie macrophytes, periphyton and phytoplankton). For example, exposure to herbicides can lead to increased internal herbicide concentrations and decreased photosynthesis, cell division, and amino acid production in plants. Impacts on aquatic plants can indirectly affect fish and invertebrates by altering habitat and food availability.
Exposure to herbicides can also directly increase mortality and alter the behavior and reproduction of fish, amphibians and invertebrates. Possible behavioral changes include increased drift by invertebrates and increased avoidance by fish.
Ultimately, these effects can lead to changes in community structure (e.g. reduced wealth, changes in functional food groups) and ecosystem functions. For example, aquatic vegetation is particularly susceptible to herbicides, so it can decrease in abundance and richness. As a result, the relative abundance of invertebrate groups that feed can change. However, herbicide-resistant plants and other non-target plants may increase in abundance due to reduced competitive pressure from affected herbicide-exposed plants.
literary criticism
This section contains an annotated bibliography of references providing information on stress-response relationships for herbicides and general background on herbicide properties. This is not intended to be an exhaustive bibliography of references dealing with herbicides, but rather to highlight a few references that may be particularly useful.
- Kegley SE, Hill BR, Orme S, Choi AH (2010)Pesticide Action Network Pesticide Database. Pesticide Action Network, North America, San Francisco CA.
This database contains toxicity data for pesticides for many species. It offers a good starting point for finding data on the use, occurrence and effects of pesticides on the Internet.
- Ross MA, Kinder-DJ (1996)Summary of the mode of action of herbicides. Purdue University, Department of Botany: Plant Pathology, West Lafayette IN. Report No. WS-23-W.
This publication provides a breakdown of seventy-eight common herbicides, organized by translocation mechanism and then by mode of action. In addition, the information is divided into chemical type, and then into common and trade names. A brief paragraph describes each mode of action and types of vegetation that the herbicide typically controls.
- Stenersen J (2009) Chemical pesticides: mode of action and toxicology. CRC Press, Boca Raton FL.
This is an up-to-date reference for mechanistic information on the health and environmental toxicity of pesticides, including herbicides and insecticides.
- AN US EPA (2009)Aquatic Life Reference Points for Pesticide Registration. US Environmental Protection Agency, Office of Pesticide Programs, Washington DC.
The aquatic life reference points (for freshwater species) provided in this module are based on toxicity values reviewed by the US EPA and used in the agency's most recent risk assessments developed as part of the pesticide (including herbicide) registration decision-making process. Acute and chronic reference points are provided for fish, invertebrates, and aquatic plants. The benchmark table contains links to support environmental risk assessments. Each aquatic reference point is based on the most sensitive and scientifically acceptable toxicity endpoint available to the US EPA for a particular taxon. The goal of the US EPA is to raise these benchmarks annually.
references
- Belden J, Lydy MJ (2000) Effect of atrazine on organophosphate insecticide toxicity. Chemical and Environmental Toxicology 19:2266-2274.
- Daam MA, Van den Brink PJ (2007) Effects of clopyrifos, carbendazim and linuron on the ecology of a small indoor aquatic microcosm. Archives of Environmental Contamination and Toxicology 53(1):22-35.
- Dewey SL (1986) Effects of the herbicide atrazine on aquatic insect community structure and emergence. Ecology 67(1):148-162.
- Diamond GL, Durkin PR (1997) Effects of surfactants on glyphosate toxicity, with particular reference to RODEO. US Department of Agriculture, Animal and Plant Health Inspection Service, Riverdale MD. IT WILL BE TR 97-206-1b.
- Duke SO (1990) General description of the mechanisms of action of herbicides. Environmental Health Perspectives 87:263-271.
- Folmar LC, Sanders HO, Julin AM (1979) Toxicity of the herbicide glyphosate and various of its formulations to fish and aquatic invertebrates. Archives of Environmental Contamination and Toxicology 8:269-278.
- Hall LW Jr., Anderson RD, Ailstock MS (1997) Chronic toxicity of atrazine to sago over a range of salinities: implications for criteria development and ecological risk. Archives of Environmental Contamination and Toxicology 33:261-267.
- Hayes TB, Stuart AA, Mendoza M, Collins A, Noriega N, Vonk A, Johnston G, Liu R, Kpodzo D (2006) Characterization of atrazine-induced gonadal malformations in African clawed frogs (Xenopus laevis) and comparisons with effects of an androgen antagonist (cyproterone acetate). ) and exogenous estrogen (17B-estradiol): support for the demasculinization/feminization hypothesis. Environmental Health Perspectives 114 (Supplement 1): 134-141.
- Kegley SE, Hill BR, Orme S, Choi AH (2010)Pesticide Action Network Pesticide Database. Pesticide Action Network, North America, San Francisco CA.
- Kreutzweiser DP, Capell SS, Sousa BC (1995) Effects of hexazinon on invertebrate and periphytonic communities in streams. Toxicology and Environmental Chemistry 14(9):1521-1527.
- Larson DL, McDonald S, Fivizzani AJ, Newton WE, Hamilton SJ (1998) Efectos del herbicida atrazina enAmbystoma tigrinusMetamorphosis: duration, larval growth and hormonal response. Physiological Zoology 71(6):671-679.
- Lydy MJ, Linck SL (2003) Evaluation of the effects of triazine herbicides on organophosphate insecticide toxicity to earthwormsEisenia fetida. Archives of Environmental Contamination and Toxicology 45:343-349.
- Ross MA, Kinder-DJ (1996)Summary of the mode of action of herbicides. Purdue University, Department of Botany: Plant Pathology, West Lafayette IN. Report No. WS-23-W.
- Scribner EA, Thurman EM, Zimmerman LR (2000) Analysis of Selected Herbicide Metabolites in Surface and Groundwater in the United States. Environmental Science Total 248(2-3):157-167.
- Shepard JP, Creighton J, Duzan H (2004) Forest herbicides in the United States: a review. Wildlife Society Bulletin 32(4):1020-1027.
- Stenersen J (2009) Chemical pesticides: mode of action and toxicology. CRC Press, Boca Raton FL.
- Streibig JC, Kudsk P, Jensen JE (1998) A general model of joint action for herbicide mixtures. Pesticide Science 53(1):21-28.
- Tate TM, Spurlock JO, Christian FA (1997) Effect of glyphosate on the development ofPseudosuccinea columelaSchnecken. Archives of Environmental Contamination and Toxicology 33:286-297.
- Tillit DE, Papoulias DM, Whyte JJ, Richter CA (2010) Atrazine reduces reproduction in fathead minnows (Pimephales Promelas). Aquatic Toxicology 99(2):149-159.
- AN US EPA (2003)Ambient Aquatic Life Water Quality Criteria for Atracin: Revised Draft.Office of Water, Office of Science and Technology, Division of Environmental and Sanitary Criteria, Washington DC. EPA-822-R-03-023.
- US EPA (2007) Technical report on the potential of atrazine to affect gonadal development in amphibians. Environmental Protection Agency, Office of Pesticide Programs, Washington DC.
- AN US EPA (2009)Aquatic Life Reference Points for Pesticide Registration.US. Environmental Protection Agency, Office of Pesticide Programs, Washington DC.
- AN US EPA (2009)Water quality criteria for aquatic life in the environment for acrolein.Office of Water, Office of Science and Technology, Division of Environmental and Sanitary Criteria, Washington DC. CAS registration number 107-02-8.EPA/822/R-09/010
- USGS (2010) The herbicide glyphosate is found in many Midwestern streams, antibiotics are not common. US Geological survey
- Van den Brink PJ, Crum SJH, Glystra R, Bransen F, Cuppen JGM, Brock TCM (2009) Effects of a herbicide-insecticide mixture on freshwater microcosms: risk assessment and chain of ecological impacts. Pollution 157:237-249.
- Van den Brink PJ, Hartgers EM, Fettweis U, Crum SJH, Van Donk E, Brock TCM (1997) Sensitivity of macrophyte-dominated freshwater microcosms to chronic concentrations of the herbicide linuron. Ecotoxicology and Environmental Safety 38:13-24.
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