Burdock Can Cause Eye Irritations

Published on Fri, 07/29/2022 - 10:00am

Burdock can Cause Eye Irritations

By Heather Smith Thomas

Burdock is an invasive plant, brought to this country many years ago.  The tall burdock plant is a native of Eurasia, probably brought to North America by seed burrs stuck to imported animals.  This biennial puts forth clusters of round burrs after it flowers during its second year of growth.  The prickly burrs get caught in the hair coat of livestock and other animals, spreading seeds via these animals. 


The tenacious burrs are a very effective way to spread the seed.  This is an amazing mechanism the plant has developed for attaching its seeds to whatever is passing by.  The creator of Velcro ™ copied this method for his invention.  If you look at the tiny burr slivers with magnification, their hooks are almost identical to a Velcro ™ fastener.

The seeds can also be spread if the plants are accidentally baled in hay or straw.


Burdock blooms in late summer, producing a composite seedhead which matures by mid-August in southern areas and later in northern climates.  Ripe burrs consist of hundreds of tiny barbed slivers, and if these get into an animal’s eye they cause severe irritation—especially if they get caught under an eyelid where they continually scrape the eyeball every time the animal blinks.


The actual cause inflammation and infection that may be puzzling, since the microscopic sliver is not easily seen.  The cornea of the eye may become inflamed and ulcerated in the injured area; the eye may turn cloudy and have an ulcerated spot.


In cattle the problem 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 an eye in fall or winter after burrs are ripe.  A sliver may become embedded in the eyelid, where it scratches the eye every time the animal blinks, creating an ulcer on the eyeball.  The sliver is so small that the usual tools used by a veterinarian to examine an eye (focal light and magnifying lens) may not be powerful enough to locate the foreign object. 


    Carl Dahlen, Beef Specialist, North Dakota State University, says it’s hard to know how many cases of “pinkeye” are actually pinkeye. “All we see is an irritated eye and an ulceration.  Most of our winter ‘pinkeye’ is due to some kind of irritation that allows micro-organisms to proliferate.  The eye problem is preceded by some type of insult to the surface of the eye.  It might be windy conditions blowing dust or chaff into the eye, or something like burdock caught under an eyelid,” he says.  The scratch on the cornea allows access by pathogens, causing an eye infection.


    Gerald Stokka, Associate Professor of Animal Sciences, North Dakota State University has seen many eye problems in livestock and says proper diagnosis is important.  “Typically, if it’s an infectious problem caused by bacteria or a virus or a mycoplasma associated with it, it appears as an outbreak.  Initially, you may get one or two animals with an eye problem and then you’ll get more,” he says.


    “True pinkeye, a bacterial infection, causes weeping (the first thing you’ll notice), and if you look closely and carefully into the eye, you will see redness of the conjunctiva, the covering of the white part of the eye.  It is trying to get more blood to that area.  You’ll see a little ulcer start to form, and it’s usually in the middle of the cornea rather than off to one edge.  This can be a clue,” says Stokka.


    “If the ulcer occurs some other place than in the center, you may be dealing with something like a sticker, plant awn or some other foreign body that got stuck under the eyelid and scraped the cornea.  To make the diagnosis—and this is difficult if cattle are out on large pastures—you must confine the animal and look into the eye,” he says.


    “You need a good light, to see something as small as a plant awn or a hair that’s scratching on the cornea every time the eye blinks.  The eye is very sensitive to scratches.  Even if the foreign matter is no longer there, if the scratch is significant enough, there are always bacteria present that could cause an eye infection.  This may take a while to clear up,” Stokka says.


     Burdock slivers are harder find than most plant material.  “You must be diligent in your search, and the animals don’t like you doing that.  It helps to have the animal restrained in a headcatch, with a halter to pull the head to one side.  Then use your fingers to peel back the eyelids and take a look both top and bottom, and in the front corner where the third eyelid is located, to see if you can find anything,” says Stokka.


    “I often use a tissue or lens paper to try to wipe something out of the area.  Even if I can’t see anything, I’ll still wipe it.  Sometimes I’ve been successful, even when I can’t identify anything there, just by wiping the area.  This might pull it loose and get it out of there, if it’s a tiny particle like a burdock sliver.  There is a lot of pain, and it will give the animal relief if you can remove the foreign body or wipe it out of the eyelid,” he says.


“If there’s an infection in that eye, I’ll prescribe an antibiotic.  If a human has a scratch on the eyeball, the doctor prescribes antibiotic drops to put in many times a day.  An irritated eye waters a lot and washes the antibiotic out.  We can’t keep repeating topical medication with cattle so we use a systemic antibiotic in hopes it will get into the bloodstream and tears, and be applied over the eyeball via tears,” Stokka says.


    In years past, many veterinarians injected a small amount of antibiotic under the surface of the conjunctiva or inner surface of the eyelid, for longer-lasting effects than topical eye medications.  This is still very effective but most veterinarians today prefer to use a systemic antibiotic labeled for pinkeye that can flood the eye via the tears, because it is easier to administer.


    Burdock can be a frustrating problem, often causing eye infections in late fall and winter when cattle are grazing in areas with thick patches of these plants.  Burdock occasionally gets baled up in hay or straw, and when the burrs get broken up in hay or bedding 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.

Controlling Burdock

“Eye irritations are common and we don’t have a good way to prevent them,” says Dahlen.  “Getting rid of burdock patches in a field/pasture can help prevent irritation from burrs, however.  Spraying these plants at the right time of year, or chopping them down before burrs are ripe can help.  We’ve used a little tractor with a brush hog to drive through every pasture and chop down those patches.  In places you can’t drive to, you end up chopping them by hand,” he says.


    “Ranchers may not be as concerned about the eye issues as just the fact that burdock takes over certain areas of the pasture.  It competes and crowds out other plants and nothing else grows there,” says Dahlen.


Several broad-leaf herbicides will kill burdock, if applied properly, according to Dr. Don Morishita, University of Idaho Professor of Weed Science and Extension Specialist (now retired).  “Burdock is a biennial; it lives for two growing seasons.  The first year, it doesn’t grow tall or bloom; it merely stores reserves in its roots,” he says.


The second year it grows a deep taproot, and a tall stalk, producing flowers and burrs.  This exhausts the food reserves in the root, and the plant dies after the 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 plants are 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.  Apply spray when the plant is putting food into the root, since you have to get herbicide into the root to kill the plant.  Use a broad-leaf herbicide like 2,4-D that can move down into the root.  If you spray early in the spring you generally kill 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).  You must spray early to get the second-year plant.  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,” Morishita says.


“Fall is a good time to spray burdock, to kill young plants that are storing 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, 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.


The main thing to remember when using herbicides to kill burdock or other biennial and perennial weeds is to not 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 the leaves survive long enough to transfer herbicide down into the root, to kill the whole plant.  Use the recommended rate (2 to 3% solution of 2,4-D which is about .5 to 3.75 ounces per gallon of water) and spray lightly--until plants are barely wet but not dripping,” he explains.


He cautions against using anything other than broadleaf herbicides.  “Burdock doesn’t grow well where there’s a lot of grass cover or other competing plants.  Don’t use Roundup, since it kills everything--including grass that inhibits regrowth of 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 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,” says Morishita.


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 seed in the ground--from earlier years--that will sprout and grow.  Keep checking the patches and get rid of new plants that grow up 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.  There are multiple reasons to try to eliminate these noxious plants in your pastures.