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Milestone (2 lb ai aminopyralid) Labels Pending Indiana
Milestone and ForeFront are labeled for permanent pastures, conservation reserve program, wildlife areas, and several non-crop areas. The active ingredient aminopyralid is good to excellent on several thistles and annual and perennial weeds such as common ragweed, horseweed, dock species, and some buttercups. Aminopyralid is in the herbicide family of pyridine carboxylic acids. Other herbicides that have active ingredients that belong to this family of herbicides are Crossbow [triclopyr + 2,4-D], Stinger [clopyralid], Transline [clopyralid], Tordon [picloram]. Two issues with the use of these herbicides should be taken into account. Both of these issues have to do with the chain of events after an application of these products. When using these products and other herbicides, it is important to consider what is going to be done to the site after application. Not only do we have to consider this for rotational aspects but for environmental reasons. In some cases it is also important to consider what the vegetative material sprayed is going to be used for after application.
Excellent
Good
Fair
Cocklebur
Wild parsnip
Multiflora rose
Lambsquarter
Buttercup spp.
Common Chickweed
black nightshade
Oxeye daisy
Common ragweed
Ironweed
Giant ragweed
Common pokeweed
Common burdock
Black locust
Bull thistle
Musk thistle
Canada thistle
Bedstraw spp.
Wild carrot
Dandelion
Dock spp.
Horsenettle
Stinging nettle
Taken from the 2009 Weed Control Guidelines for Ohio and Indiana - Guide
Residual activity – Pyridine carboxylic acids can remain in soil and plant residue for some time. The halflife of aminopyralid, clopyralid, picloram and triclopyr are approximately 34.5, 40, 90 and 30 days, respectively8. This is dependent on the soil and environment. Picloram has been reported to have a half-life of 300 days in some conditions. This leads to the need to know what is going to happen to the land and plants where these herbicides could be applied.

In one scenario that occured, an application is made by a company or one family member to an old stump then the stump is put though a chipper, then the mulch is sold to a third party. The third party, possibly a neighbor, uses the mulch not realizing that herbicide was used and that residues may still be in the mulch. It has happened. The same situation can happen with chipped shrubs and trees that have originally been sprayed. The Milestone label states “Do not use aminopyralid-treated plant residues, including hay or straw from treated areas. . . in compost or mulch that will be applied to areas where commercially grown mushrooms or susceptible broadleaf plants may be grown.”

Movement in the animal - Herbicides that have these active ingredients generally do not have grazing restriction for non-lactating animals but the labels will generally require the animals be grazed on non-treated forages for 3 days before the animals can be moved to pastures of sensitive crops. The reason for this is that the herbicide simply passes though the animals on the food they consume. The herbicides in this family are not altered as they pass through the animal’s body and can be found in the urine and manure produced by the animal. If the animal is moved from a treated pasture or fed feed from a treated pasture then moved to a pasture with legumes or other sensitive broadleaf crops, injury of those sensitive crops will occur. One way to think of this is if the animal has been feeding on treated feed, when the animal relieves its self, it is essentially making a herbicide application. Rotation restrictions state that to switch from pasture to a sensitive crop, a one year period has to occur before planting. The use of a bioassay is recommended. It might be safe to assume that if you move cattle from a treated pasture to a non-treated pasture you may be making a herbicide application, and the one year rotation restriction could imply even though you have not applied the herbicide directly to the pasture. In one case experienced in 2008 in Indiana, cattle were fed treated feed, and then moved to a grass/legume mixed pasture where the legumes started to show growth regulator injury.
       
Updated 1/8/09

Information listed here is based on research and outreach extension programming at Purdue University and elsewhere.
The use of trade names is for clarity to readers of this site, does not imply endorsement of a particular brand nor does exclusion imply non-approval. Always consult the herbicide label for the most current and update precautions and restrictions. Copies, reproductions, or transcriptions of this document or its information must bear the statement ‘Produced and prepared by Purdue University Extension Weed Science’ unless approval is given by the author.
       
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Milestone