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How to eradicate Horse weed from 40% of a yard #876666

Asked July 10, 2024, 12:33 PM EDT

Email: <personal data hidden> About 40% of my yard is infected with Horse weed. Glysophate is not the viable solution.I have 19 new trees and 3 gardens...and pets. > It's possible it came from infected topsoil bought from Gertens. I understand this weed aggressively spreads with 200k seeds per plant.. and my neighbors are getting now too. > how to eradicate it? > if gone, how can I keep it from coming back...especially if removing it is costly, and either adding new seed or rolls of sod. With that amount of seed, how is it spreading...rabbits and squirrels? Air borne? Some advice I got. Solar starvation, which I'm trying in a small area, but I heard the plants can grow horizontally with dark plastic. Cardboard? > Many weed specialists even at nurseries, have not heard of it nor know how to eradicate it. > Some of my research says it it's common in farm fields. I'm guessing if it was from the topsoil i bought, Gertens likely scooped farm soil and resold it. I have no real solid idea of what to do. > By watching it recently, spreading to the neighbors, I'll guess it'll be a serious problem spreading across neighborhoods in a season.

Hennepin County Minnesota

Expert Response

Thank you for the articles.  It is good information.
However,  I have a Horse weed infestation in my residence.
Glysophate is not a viable option as it will kill ALL plants and trees.
> it will sicken local animals and birds as well as pets.
Extremely harmful to human contact.
> Given, if it can be eradicated,  and to what expense that will take,
> are there any preferred methods of re sodding  whereas the horse weed will not affect it again...next season?

If I leave this to be....its only a matter of time before it spreads throughout the neighborhood...then more.
It sounds like lawn service weed control cannot treat it


On Wed, Jul 10, 2024, 4:27 PM Ask Extension <<personal data hidden>> wrote:
The Question Asker Replied July 10, 2024, 6:22 PM EDT

Thank you for your question regarding the elimination of horseweed. It has been referred to me.

To start, look at the following. It is an excellent description of the plant and its life cycle:

https://growiwm.org/weeds/horseweed-marestail/ - :~:text=Burndown herbicides, such as 2,or spring to control horseweed.

Dealing successfully with horseweed requires a bit of background information about the plant. It is an annual plant having a relatively shallow root structure. It has a single taproot. It can be pulled up rather easily. Its primary way of spreading is via the production of an enormous number of seeds. As you correctly pointed out in your question, this can be over 200,000 seeds per single plant. Wind dispersal is the major way for their distribution. So one control strategy is to pull the plants up prior to their blooming. It seems that you may be dealing with a large area so this tactic may not be realistic.

But what you can do now is to apply a broad-leaf herbicide. This needs to be done ASAP and prior to their blooming. Killing plants after they have released their seeds achieves nothing. Look for an herbicide containing 2,4-D or Dicamba. Read the product label to be sure that it is effective against horseweed. To ensure safety for people and animals, scrupulously follow the application instructions. Herbicide resistance is well documented for horseweed. Usually this resistance is against such things as glyphosate and not herbicides containing the two compounds just mentioned. To cover your bases, use an herbicide that contains both 2,4-D and Dicamba or use two different herbicides containing either one or the other compound. Horseweed can bloom for much of the summer. So a single application of herbicide will not cut it. Plan on doing applications at three different times: now (early July 2024), early August 2024, and then in early September. The overall goal is to kill the plants before they produce and release seeds. Be aware that these herbicides will also kill established plants, both annual and perennial. This can’t be avoided. Try to use direct spraying of these herbicides onto just the horseweed. There is no herbicide that will kill only horseweed and nothing else. See:

https://www.extension.purdue.edu/extmedia/gwc/gwc-9-w.pdf

Some of the seeds produced in 2024 will germinate this fall. Others will germinate spring 2025. To counteract this latter possibility, apply a pre-emergent herbicide in late April to early May 2025. Look for a product containing oxadiazon, dithiopyr, and/or prodiamine. See:

https://www.nurserymag.com/article/glyphosate-resistant-horseweed-control/

https://growiwm.org/weeds/horseweed-marestail/ - :~:text=Burndown herbicides, such as 2,or spring to control horseweed.

I understand your concern regarding the use of glyphosate. I share it as well. Using one or more of the herbicides I’ve described, will be a bit safer. Complete elimination of horseweed will take at least three or four seasons.

Good luck. Please feel free to get back to us if we have not adequately answered your question or if you have additional, related questions. Thanks for using our forum

An Ask Extension Expert Replied July 10, 2024, 10:27 PM EDT

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