Need info on herbicide that kills Stiltgrass

[danacat]

I have now lost almost half of one of my pastures to a monoculture of Japanese Stiltgrass (Microstegium vimineum) – it’s slowly been overtaking this 4 acre pasture – remarkable that this invasive grass does so well in full sun.

I’ve been taking measures to erradicate it, but the seed bank must be high + all the rain we had this year caused an explosion of it. Anyway, I have to resort to using an herbicide.

There is a product made by Bayer called Acclaim Extra – active ingredient is: fenoxaprop-p-ethyl. It very effectively kills stiltgrass at low concentrations (won’t harm other grasses) + it is legal in NY. However, it is not labeled for use in pastures.

I called Bayer to find out why and got nowhere with the customer service person I spoke to – only explanation they offered was: Not for use in pastures. Okay…but what if I keep the horses off the pasture for a week, a month, a year? I further pressed for more detailed answers like how fast it degrades in the soil, is it absorbed by other grasses that will poison a horse if they eat it, etc. etc. and still got nowhere = Not for use in pastures was all they would say. Hmmmm.

So I then researched fenoxaprop-p-ethyl- which besides lawns and recreational areas is used in certain crop fields that produce grains for human consumption – but was still unable to find the answers I was looking for.

Has anyone used Acclaim Extra – does anyone know anything about it or want to venture a guess as to why it can not be used on pasture?

[danacat]

@danacat

… want to venture a guess as to why it can not be used on pasture?

Maybe this is an answer to my own question – in part:

So stiltgrass gets sprayed with non-horse pasture allowed herbicide. Stiltgrass dies and leaves behind residual plant particles = dried up stuff still laden with herbicide. Horses come along and eat this = injest herbicide = god knows what reaction because herbicide has either not been tested on horses (only mice etc.) or already is know to contain an active ingredient that should not be eaten by any mammal in any quantity.

So it then makes sense that no grazing animals should be put on herbicide treated ground until all residual traces of dead stiltgrass are gone (total decomposition) and ground is growing healty stand of pasture grass in its place.

I can’t imagine no grazing ever after an area is treated. There has to be a time factor. I just don’t know what that is specifically, other then the timing it takes for treated plant material to be gone.

[NoSuchPerson]

Pesticides are registered by EPA for specific uses and different kinds of data may be required for different uses. If a company feels like it won’t make enough money from selling a particular product for a specific purpose to offset the costs of getting it registered for that use, they won’t bother doing it. This most commonly becomes an issue when a pesticide goes through registration review and EPA will ask for additional data to support certain uses and the company will decide to just cancel the use rather than spend the money to conduct the additional studies.

It doesn’t necessarily mean that the pesticide is unsuitable for that use or that there is some problem with using the pesticide for that use. It may just be an economic issue. It’s recognized as a problem, EPA has a minor use program that addresses some of these concerns.

I realize that none of this helps your particular problem, but may explain why Acclaim Extra can’t be used on pasture. And I’m not surprised that Bayer wouldn’t tell you anything beyond that the product isn’t registered for use on pasture. There is too much potential liability if they told you anything that might, by any stretch of the imagination, be interpreted as encouragement to use their product for an unregistered use.

[Garythesquirrel]

You could spray with glyphosate, which would kill everything off, and reseed.

[danacat]

@NoSuchPerson

If a company feels like it won’t make enough money from selling a particular product for a specific purpose to offset the costs of getting it registered for that use, they won’t bother doing it. This most commonly becomes an issue when a pesticide goes through registration review and EPA will ask for additional data to support certain uses and the company will decide to just cancel the use rather than spend the money to conduct the additional studies.

It doesn’t necessarily mean that the pesticide is unsuitable for that use or that there is some problem with using the pesticide for that use. It may just be an economic issue.

This makes sense. Could very well be the case.

Interesting though that Bayer wouldn’t want to register – for pasture use – an herbicide that specifically targets an invasive grass species and doesn’t harm orchard grass and some other pasture grasses. They could make $$ with a product like that, especially since similar products by other companies: Milestone for example that also effectively kills stiltgrass, but isn’t allowed in certain states.

[Where_sMyWhite]

Contact your local county extension agent. They should (I can really only speak to the county I live in ) have access to people who deal with turf, pasture, herbicides, etc. If you first contact them and don’t get a response, start leaning on them. Also contact your state land grant university directly.

I am a certified Master Gardener for the county I live in. I’m not qualified to talk about herbicides but I know I have access to staff who are far more qualified than I am if I need them

[danacat]

@Where'sMyWhite

Contact your local county extension agent. They should (I can really only speak to the county I live in ) have access to people who deal with turf, pasture, herbicides, etc. If you first contact them and don’t get a response, start leaning on them. Also contact your state land grant university directly.

I spoke with an agent yesterday – as expected he was no help as to why certain herbicides are not labeled for pasture, but he did inform me that certain pasture friendly herbicides that were not legal in NY – now are. And we went over the ones that might work for stiltgrass. He also was very surprised that the stiltgrass I have is thriving in full sun.

I then got hold of a really nice and very informative gal from Corteva, a division of Dow Agro sciences, and she was forthcoming, saying simply that the research for non pasture use herbicides on pasture, has not been done, just what @NoSuchPerson said – but that doesn’t mean that it wouldn’t be safe. She then gave me the contact info for another Dow employee who specifically studies the herbicides in the field in my area – he might have the info I’m looking for etc.

[Palm_Beach]

I’ve been using ProwlH20 which works well until this time of year. There is something new and better, I will try to find out for you today. My neighbor used it and said it worked great.

[ShotenStar]

Stiltgrass is wrecking my pastures as well. And the County Extension folks think I’m a little weird for insisting that is adapting to growing in full sun, but I have proof every time I walk my fields.

I also did the rounds of researching various herbicides and tried a pre-emergent one year. Stiltgrass is an annual, like crabgrass, and is prolific seed producer. The pre-emergent did reduce the amount of stiltgrass that one year, but it had a 45-day grazing restriction - too high a price for me to consider using a second year. So now I use fall mowing as my only control strategy. We mow just as seed heads are starting to form and mow again a few weeks later to catch any new seed heads. This is only a partially successful tactic since I live next to a State Park that is an endless reservoir of seeds.

The bottom line for me is that I have given up searching for any full-control measures and have settled for maintenance techniques.

star

[Mango20]

Same here, it’s been creeping across my pasture starting from the shady side and into the sun. Most of mine is still at least partially shady, but there are some outcroppings in full sun. I also try to mow it at the right time to prevent some seeds from forming, but I think it’s kind of a lost cause.

[KJag550]

I am new to maintaining pastures but am having the same issue in a field we plan to fence. My father had suggested 24D.

[Palm_Beach]

Milestone. Works great, no grazing restrictions.

[NoSuchPerson]

@Palm Beach

Milestone. Works great, no grazing restrictions.

I don’t think you can use Milestone on pasture in New York.

[Palm_Beach]

@NoSuchPerson

I don’t think you can use Milestone on pasture in New York.

Yes, you can, except Nassau and Suffolk Counties.

https://www.corteva.us/labels-and-safety-data-sheets.html?pid=3057&pdpSrc=agrian

[danacat]

@Palm Beach

Yes, you can, except Nassau and Suffolk Counties.

Correct ^^^. But there are restrictions insofar as using manure for compost from horses grazing in a Milestone treated pasture. – you can’t for 18 months. All manure + any baled hay must stay on the farm because Milestone is very persistent in the soil for this time frame – of course it depends on the amount used + soil type + weather etc. that will determine how long it will take for Milestone to break down and not be a garden plant killer via composted manure.

But manure is clear of Milestone after 3 days of grazing on a non-Milestone treated pasture – but once horses go back to grazing in the treated pasture (before the 18 month time frame) manure will be laden with Milestone again and again you can’t compost.

Milestone is very effective on Stiltgrass so long as it is sprayed on seedings in the spring once they reach a growth habit of no more than 4 leaves but more than two (if I remember correctly) so timing has to be just right for upwards of a 75% kill off. But if the seedbank in the soil is high, then the following year (or sooner) those dormant seeds will probably sprout and you have to start all over again.

The key is lower the seed bank by not letting ANY more stiltgrass seed get into the soil – this often means a 2-4 year management plan = Milestone (or other herbicide) + mowing + pulling it out by hand.

This year in mid Sept. I hand pulled tons of the stuff out of my pasutres just as it was setting seed. Very labor intensive – but all those seeds are now NOT in my pastures.

[Palm_Beach]

@danacat

Correct ^^^. But there are restrictions insofar as using manure for compost from horses grazing in a Milestone treated pasture. – you can’t for 18 months. All manure + any baled hay must stay on the farm because Milestone is very persistent in the soil for this time frame – of course it depends on the amount used + soil type + weather etc. that will determine how long it will take for Milestone to break down and not be a garden plant killer via composted manure.

But manure is clear of Milestone after 3 days of grazing on a non-Milestone treated pasture – but once horses go back to grazing in the treated pasture (before the 18 month time frame) manure will be laden with Milestone again and again you can’t compost.

Milestone is very effective on Stiltgrass so long as it is sprayed on seedings in the spring once they reach a growth habit of no more than 4 leaves but more than two (if I remember correctly) so timing has to be just right for upwards of a 75% kill off. But if the seedbank in the soil is high, then the following year (or sooner) those dormant seeds will probably sprout and you have to start all over again.

The key is lower the seed bank by not letting ANY more stiltgrass seed get into the soil – this often means a 2-4 year management plan = Milestone (or other herbicide) + mowing + pulling it out by hand.

This year in mid Sept. I hand pulled tons of the stuff out of my pasutres just as it was setting seed. Very labor intensive – but all those seeds are now NOT in my pastures.

If you choose to pull it out by hand wow, you have more of a work ethic than me. I don’t compost either, too much of a waste of time. Simply sharing what works good in my area.

[danacat]

@Palm Beach

If you choose to pull it out by hand wow, you have more of a work ethic than me.

When horses on a particular pasture have little real grass to eat (due to stiltgrass invasion) your work ethic gets pretty darn strong! I am at war with stiltgrass! A few years ago brown knapweed was my enemy – I have won that war.