By Heather Smith Thomas — Eye problems in livestock and horses can be caused by foreign material in the eye, and one of the most challenging problems is burdock slivers. Burrs from this invasive weed stick to hair or clothing. When ripe, the burrs release hundreds of microscopic barbed slivers that contain tiny seeds. If a sliver gets into an eye, it can cause inflammation and infection. The cause of infection may be difficult to discover, however, since the microscopic sliver is hard to see. The eye may become inflamed and ulcerated, turn cloudy and have a white spot or bulge on it.
In cattle, this may be mistaken for pinkeye, but pinkeye is generally a summer problem when face flies spread infection from animal to animal. By contrast, burdock slivers usually get into the eye in fall or winter after burrs are ripe, and become embedded in the eyelid. This scratches the eye every time the animal blinks, creating an ulcer on the eyeball and infection. The sliver is so small that the typical light and magnifying lens used by a veterinarian may not be powerful enough to locate it.
Pinkeye infection causes weeping eye-watering, and if you look closely at the eye, the white part is red. Ulceration is usually in the middle of the cornea rather than off to one edge. If the ulcer appears some other place than in the center, it may be from a sticker or seed that got stuck under the eyelid and scraped the cornea.
Restrain the animal so you can look at the eye with a good light to see if there’s a plant awn or a hair under the lid scratching the cornea every time the eye blinks. Even if the foreign material is no longer there, if the scratch is significant there are bacteria present that could cause an infection. Burdock slivers are hard to locate.
If it’s a horse with a sore eye, you’ll need your veterinarian to possibly sedate the horse or anesthetize the area so he/she can examine the eye without protest from the horse. For livestock, you’ll need the animal restrained in a head-catch, with a halter to pull the head to one side. Then use your fingers to peel back the eyelids and take a look at both top and bottom, and in the front corner where the third eyelid is located, to see if you can find anything caught in there.
You can use a tissue to wipe something out of that area. Even if you can’t see anything, wipe the area. This might pull a microscopic sliver loose and get it out of there. A foreign body causes a lot of pain, and if you can remove it or wipe it out of the eyelid, this will give the animal relief.
If there is an infection in the eye, your veterinarian can prescribe an antibiotic. If a human has a scratched eyeball, the doctor prescribes antibiotic drops to administer several times a day because an irritated eye waters and washes out the antibiotic. We can’t keep repeating topical medication with cattle, however, so we use a systemic antibiotic (usually in injectable) that will get into the bloodstream and tears, and then it can flow over the eyeball via the tears.
Burdock plants can be a frustrating problem. Burrs occasionally get baled up in hay or straw. When the burrs get broken up and float around in the air (if the animal shakes it up, or it blows in the wind), tiny slivers can end up in the eyes.
Getting rid of burdock plant patches in a field/pasture can help prevent these problems. You can spray burdock plants at the right time of year, or chop them down before burrs are ripe. You can use a small tractor and bush hog, or chop the plants by hand in places where you can’t drive. Even if you are not worried about eye issues, burdock plant should be eradicated because it spreads and takes over certain areas crowding out other plants.
Several broad-leaf herbicides will kill burdock if applied properly. Burdock plant blooms in late summer, producing composite seed heads (burrs) by mid-August in southern areas and later in northern climates. Burdock plant is a biennial, living for two growing seasons. The first year, it doesn’t grow very tall or bloom; it merely stores reserves in the roots, like a carrot (which is also a biennial).
The second year, it grows a deep taproot, a tall stalk, flowers, and burrs. This exhausts the food reserves in the root; the plant dies after burrs are mature. After the stalk comes up, it is harder to kill with herbicides because the plant is sending food up from the roots instead of down.
Burdock plant is easiest to kill in early spring or in the fall. The first-year plant stays in rosette stage that first summer (circular cluster of leaves, no tall stalk) and this is the easiest time to kill it with spray — when the plant is putting food into the root — since you have to get herbicide into the root to kill the plant. If you spray early in the spring you generally kill the new young sprouts and last year’s rosettes (plants that are trying to create more food reserves in the roots for their big push to complete second-year growth and make burrs). After the stalk comes up it’s harder to kill. If you spray in the fall you are killing this year’s rosettes — plants that would mature and create burrs next year.
Fall is a good time to spray to kill the young plants that are storing food reserves in their roots for next year’s growth. The first hint of cold weather is a trigger to send food to the roots. By contrast, in spring the second-year plant is taking food from its roots to produce leaves and make the big push for a tall stalk and blooms. The food is going up and it’s harder to get herbicide down into the root. Food reserves in the root are lowest when the plant starts to bloom.
When using herbicides to kill burdock or other biennial and perennial weeds, don’t overdo it. If you use too much, it quickly kills the leaves and doesn’t get down into the taproot. The root survives, to regrow. You want slower kill so leaves survive long enough to transfer herbicide down into the root to kill the whole plant. Use only broadleaf herbicides. Burdock doesn’t grow well where there’s a lot of grass. Don’t use a spray that kills everything; you want the grass to survive because it competes with the burdock.
Chopping burdock is effective, but you must do it at the right time or the plant will regrow. The best time to chop it down is after the stalk is budding but before burrs are ripe. At that point, the food reserves are so low in the root that it cannot regrow. It may take several years of diligent control to eradicate burdock since seeds can live a long time. Even though you chop or spray the plants, there may be viable seeds in the ground — from earlier years — that sprout and grow. Keep checking the patches and get rid of new plants that grow from old seeds. Unless controlled, burdock is readily spread to new areas by burrs stuck to animals. Livestock and wildlife spread this tenacious weed to other fields and pastures. Cattle buyers may refuse to purchase animals that are covered with burrs.
Have you had problems with burdock plants in your pastures? How did you eradicate it?