by Scott Wright, Dow AgroSciences
Adapted from Transmission and Distribution World - Vegetation Management
When applying herbicides on lands grazed by livestock, vegetation managers must read and understand product label information regarding grazing tolerances. Failure to do so can lead to unintended consequences such as off-target damage to desirable vegetation and the rejection of livestock for human consumption. Not all herbicides have grazing tolerances established. For example, the Perspective herbicide label states, “Do no graze or feed forage, hay or straw from treated areas to livestock.” In contrast, the the Milestone® herbicide label includes grazed areas.
In a nutshell, any herbicide that is applied to land that is subsequently used for grazing must have grazing tolerances spelled out on the label. Land that is treated with herbicides lacking grazing tolerances puts the livestock who graze that land and the products of the livestock — milk, dairy products or meat — at risk of being rejected from commercial trade, economically impacting agricultural producers.
Grazing tolerances are established for herbicides by the U.S. Environmental Protection Agency. They are only established for products that have undergone stringent testing for use of the herbicide on grass, hay or other feedstock for livestock animals such as cattle, horses, sheep and goats. Additional studies conducted for grazing tolerances include: grass residue trials, lactating cow feeding study, nature of residue in a ruminant, acute, and sub-chronic toxicity.
Herbicides that have grazing tolerances may still have special use restrictions such as use rates, application methods, or instructions on how to handle hay, manure or the movement of livestock in and out of treated areas. Thus managers need to read the label and abide by any special use restrictions. Violations of the herbicide label conditions of use is considered an off-label application under the Federal Insecticide, Fungicide and Rodenticide Act (FIFRA). There are many cases where large settlements have been paid out to replace contaminated livestock.
The definition of grazed areas is also somewhat broad. It mainly refers to pasture or rangeland set aside for grazing cattle or other livestock, but can also include rights-of-ways that are grazed or hayed. Applying herbicides labeled for a wide variety of site types including lands grazed by livestock increases efficiency for vegetation managers working across a complex of grazed and non-grazed areas (e.g. rights-of-way and pastureland).
Grazing tolerances should always be considered when planning herbicide applications. Applicators setting parameters for a mix of grazed and non-grazed lands should consider only using herbicides with grazing tolerance on the label. It is important to note that even if an animal escapes from a fenced pasture and grazes an area treated with an herbicide without a grazing tolerance, that animal may be considered adulterated and cannot be sold for food.
Typically there is no cost difference or additional premium paid by a consumer for herbicides with a grazing tolerance, and these products (e.g. Milestone® and Transline® herbicides) are easily accessible from most herbicide manufacturers. It is also a good policy for rights-of-way and other managers to practice proactive landowner communication prior to herbicide application, especially in areas where grazing may be taking place. This helps alleviate landowner concerns, but also provides a forum for landowners to alert vegetation managers to areas accessible to grazing animals.
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Milestone is not registered for sale or use in all states. Contact your state pesticide regulatory agency to determine if a product is registered for sale or use in your state. Label precautions apply to forage treated with Milestone and to manure from animals that have consumed treated forage within the last three days. Consult the label for full details. State restrictions on the sale and use of Transline apply. Consult the label before purchase or use for full details. Always read and follow label directions.©2019 Corteva
Active ingredients for herbicide products mentioned in this article: Product (active ingredient). Milestone (aminopyralid), Transline (clopyralid), Perspective (aminocyclopyrachlor + chlorsulfuron)
First published May 2016; Updated June 2019