Technical Facts and Answers to Frequently Asked Questions About Milestone® Herbicide

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What is the environmental fate of Milestone® herbicide?

Soil: Aerobic microbial degradation is the primary route of breakdown in soil. Average field soil half-life is 34.5 days for eight North American sites. There are no degradation metabolites of concern.

Water: Photolysis (UV portion of the light spectrum) is the primary route of degradation in water. Photolysis half-life under standard conditions is 0.6 days. Groundwater contamination potential is low because of low use rates combined with moderate soil half-life.

Air: Practically non-volatile

Where can Milestone herbicide be used?

Milestone is labeled for use on rangeland, permanent grass pastures, Conservation Reserve Program (CRP) acres, non-cropland areas (such as roadsides), non-irrigation ditch banks, seasonally dry wetlands, natural areas (such as wildlife management areas, wildlife openings, wildlife habitats, recreation areas, campgrounds, trailheads and trails), and grazed areas in and around these sites.

What is the runoff potential of Milestone herbicide?

Milestone has a low risk of runoff in surface water compared to the current market standards. The runoff impact of Milestone® is mitigated by low use rate and rapid photolysis in water. 

What is the ecotoxicology profile of Milestone herbicide?

  • Milestone exhibits low acute and chronic toxicity to mammals, birds, fish, aquatic and terrestrial invertebrates, algae and aquatic vascular plants in laboratory studies. 
  • Risk of adverse effects is substantially below all of the EPA levels of concern (LOC) for non-target organisms.
  • Milestone produces no significant soil or water metabolites other than CO2 and NH3 and has a low bioaccumulation potential.
  • In EPA’s assessment under the Reduced Risk Pesticide Initiative, Milestone was found to have reduced acute and chronic toxicity to mammals, birds, algae and aquatic vascular plants compared to market standards.

What is the rainfast period?

Foliar absorption of Milestone® applied post emergence is relatively rapid. Milestone herbicide appears to be rainfast within two hours after application when applied at recommended label rates.

How close to water can I spray?

Milestone can be used to the waters edge but do not apply directly to water or to areas where surface water is present or to intertidal areas below the mean high water mark. Take precautions to avoid spray drift onto water. Do not spray on inner banks of ditches or canals used to transport irrigation water.

It is permissible to treat non-irrigation ditch banks, seasonally dry wetlands (such as flood plains, deltas, marshes, swamps, or bogs) and transitional areas between upland and lowland sites.

Can Milestone herbicide be used in riparian areas?

Yes, under the following guidelines:

  • The label does not allow applications directly to water (ponds, lakes, rivers, streams and irrigation canals). 
  • Avoid applications that may result in movement of Milestone into water used to irrigate crops.
  • The non-target plant community should be considered (see forb and shrub tolerance section, page 11).

How long does Milestone® herbicide persist in the soil?

  • While Milestone herbicide will provide season-long residual control of emerging broadleaf weeds, this herbicide has a moderate field soil half-life. 
  • Half-lives in U.S. and Canadian field studies have averaged approximately 34.5 days. Ninety percent of Milestone applied at a rate of 7 fl oz/acre dissipated within 90 days. 
  • In a large majority of studies, the herbicide has remained in the top six to 12 inches of the soil profile.

What effect does pH have on degradation of Milestone?

Due to the low pKa (ionization constant) of the active ingredient, pH will have no impact on Milestone degradation in any matrix.

Can Milestone® herbicide be applied with spot treatments?

Yes, spot treatments may be made at an equivalent broadcast rate of up to 0.22 lb active ingredient (14 fl oz of Milestone) per acre per annual growing season; however, not more than 50% of an acre may be treated.

Do not apply more than a total of 0.1 lb active ingredient per acre (7 fl oz per acre of Milestone) per annual growing season.

(See spot treatment calibration guidelines on page 15.)

What about surfactants?

The addition of a high quality non-ionic surfactant (of at least 80% active ingredient) at 0.25 to 0.5% volume per volume (1 to 2 quarts per 100 gallons of spray) is recommended to enhance herbicide activity under adverse environmental conditions (such as high temperature, low relative humidity, drought conditions, dusty plant surfaces), when weeds are heavily pubescent, or with more mature plants.

How long will Milestone herbicide remain active in the spray tank solution?

Milestone herbicide is not degraded by the hydrolysis process like sulfonylurea herbicides. Milestone® will break down in water when exposed to ultra-violet (UV) light from the sun. Provided the spray tank is a UV resistant tank (most are), or if the sprayer or mix tank is parked inside, the solution would be stable for very long periods of time. Although once herbicides are mixed, it is advisable to use them as soon as possible.

Are there sprayer clean-out instructions to avoid damage to sensitive plants?

Yes. It is important to not use spray equipment used to apply Milestone for other applications to land planted to crops or desirable sensitive plants unless it has been determined that all residues of this herbicide have been removed by thorough cleaning of equipment. No exceptions! See label for detailed cleaning instructions.

Will Milestone herbicide harm grasses?

Research was conducted on over 33 different grass species and both warm and cool season grasses show excellent tolerance to Milestone herbicide. In fact, grass production increases significantly after weeds are removed.

Are there grazing or haying restrictions?

Milestone passes through an animal’s digestive system unchanged and is excreted in urine and manure.  This occurs relatively rapidly, within about three days.

There are no restrictions on grazing (any livestock including lactating dairy and horses) or hay harvest following application of Milestone® at labeled rates1.

Cutting hay too soon after spraying weeds will reduce weed control. Wait 14 days after herbicide application to cut grass hay to allow herbicide to work.

Milestone does not break down in plants.  Therefore, hay from areas treated with Milestone may contain residues. Inform the recipient of hay or manure from animals grazing pastures or feeding on hay from areas treated with Milestone of the label use precautions and restrictions.

Hay from grass treated with Milestone within the preceding 18-months can only be used on the farm or ranch where the product is applied unless allowed by supplemental labeling. 

Do not transfer livestock from treated grazing areas to sensitive broadleaf crop areas without first allowing three days of grazing in an untreated pasture. Otherwise, urine and manure may contain enough Milestone® to cause injury to sensitive broadleaf plants. Refer to Milestone label for additional instructions. 

1Restrictions do apply to the transfer of grazing animals to sites intended to grow sensitive crops. Refer to the label for a complete list of transfer restrictions.