Milestone Does Not Have a Fit in Most Pasture Situations

Mark VanGessel, Extension Weed Specialist; mjv@udel.edu

Milestone (aminopyralid) is a relatively new herbicide for pastures and CRP that provides good to excellent control of many broadleaf weeds (including thistles). It has other positives as well that makes it a very tempting choice for grass pastures. However, the herbicide does not break down in the plants, or in the digestive tract of the animals, nor during the composting process. Therefore, manure from animals fed with treated hay or grazed in the treated pastures, can contain some of the active herbicide. In addition, if this manure is applied to fields or gardens with sensitive plants, they can be severely injured or killed. Broadleaf plants (especially legumes) are most prone to injury.

The following is from the Milestone label:

Do not use Milestone-treated plant residues, including hay or straw from treated areas, or manure from animals that have grazed forage or eaten hay harvested from treated areas within the previous 3 days, in compost or mulch that will be applied to areas where commercially grown mushrooms or susceptible broadleaf plants may be grown.

Do not spread manure from animals that have grazed or consumed forage or eaten hay from treated areas within the previous 3 days on land used for growing susceptible broadleaf crops.

Manure from animals that have grazed forage or eaten hay harvested from Milestone-treated areas within the previous 3 days may only be used on pasture grasses, grass grown for seed, and wheat.

Do not plant a broadleaf crop in fields treated in the previous year with manure from animals that have grazed forage or eaten hay harvested from Milestone-treated areas until an adequately sensitive field bioassay is conducted to determine that the Milestone concentration in the soil is at level that is not injurious to the crop to be planted.

Milestone is better suited in our region for use with CRP where the grasses are not harvested or grazed. Since manure management is essential to protect sensitive plants, it has no fit in pastures or hay crops in our area.

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