By: Douglas K. Daniels, DVM, & Shawn M. Devaney, DVM

The nomer “foxtail” describes this plant’s characteristic shape: It looks very much like a fox’s tail (and is also a look-alike for timothy), generally producing a graceful, curved seed head in summer. Foxtail is a summer annual grass, meaning it grows from seed in the spring and dies in the fall. It is fast-growing, hard to control, and resilient in the face of efforts to stop it from going to seed. For this annual plant to come back year after year, it drops hundreds of seeds into the soil. Within each seed head are unpleasant and barbed little members called “awns,” which can spell big trouble for your horse (or dog) after drying up in the fall. Foxtail awns are stiff, spiky fibers that can readily get bundled in your round or square bales at harvest if foxtail has gone to seed in the hayfield, which is a very common occurrence.

As a horse owner, your only protection against these awns is to inspect your horse’s hay carefully. As a hay producer, you must mow the hayfield before it goes to seed or apply the correct herbicides, which we’ll discuss later on. In our experience, we find foxtail-infested hay more commonly in round bales, because that hay is more difficult to inspect. We also see more of it after a very wet growing season, when the hay crop is in the field longer and becomes more mature than the farmer would like.

When horses eat hay contaminated with foxtail, the awns can lodge in the mouth and gums, working their way through the tissue, causing lesions, infections, and pain.

How do you know if your horse has eaten foxtail?

Signs include being off feed, mouth ulcerations, excessive salivation, and a foul odor. While mild cases usually resolve with time after you remove the offending hay, severe cases require a call to your veterinarian to sedate the horse and pluck, dig, or scrape the awns out from under the gums, the lips, and around the mouth.

Mitigating Foxtail

Because foxtail is a grass, it is nearly impossible to eradicate with herbicides that won’t also damage your desirable grasses. You have three options:

Renovate your pastures. If you have a minor foxtail infestation, you can overseed with desirable cool-season grasses (e.g., Kentucky bluegrass, orchardgrass, tall fescue) in the late summer so by springtime, the new grass shades out the foxtail seedlings. If you have a significant infestation without much desirable grass left, consider plowing it under and reestablishing the hayfield. Tilling the field will bury the seeds too deep for them to germinate. Have your local extension agency analyze the soil to recommend amendments before planting. You will also want to avoid grazing the pastures for at least six months after seeding to allow the new grasses to establish healthy root systems.

In pastures you are not able to reestablish, let foxtail grow up and begin producing seed heads, then mow it. If you keep an eye on these plants, you can tell when the seed heads start developing within the sheath. You must be able to identify the grasses without the seed head present. If you mow between this stage and full seed stage, then the plant will not be able to drop seeds for next year, and it won’t grow another seed head this year. There are three important things to remember with this method:

Like desirable forage grasses, foxtail is not deterred by mowing. You must let the grass grow tall before producing seed heads.

The foxtail seeds in your pasture might have germinated at different times in the spring. Therefore, they will not all set seed at the same time. You must watch them to know when to mow.

The soil might have a considerable seed bank. You must use these management techniques for several years before achieving control. Letting the foxtail drop seeds just once will replenish the seed bank.

Apply an herbicide. Two herbicide options can help control annual foxtail species in grass hay: pendimethalin and quinclorac. They work differently and require different control strategies. Generally, however, you should target very early spring with preemergent herbicides or immediately following the first cutting with post-­emergent herbicides. Your county agricultural extension agency is a great local information resource for herbicides and procedures for your area and climate.

Take-Home Message

If you grow and harvest your own hay, check the fields. If you find foxtail in your hay supply, contact your provider and ask for a foxtail-controlled or -free replacement. You can expect to pay more for foxtail-free hay, because the farmer will incur additional labor and costs to produce it. Considering the impact of your horses ingesting foxtail-infested hay and the associated veterinary costs, it might be a price worth paying.