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Poisonous Plant Control

Most poisonous plant losses are not mysteries. They happen when hungry cattle meet a plant they would normally leave alone, so control starts with knowing what grows on your place and when it is most dangerous.

Why plant poisonings happen when they do

Cattle usually avoid plants that taste bad or feel wrong in the mouth. The trouble starts when something takes away their choices. A short pasture in a dry spell, a new field after hauling, a hay shortage, or a sudden flush of green growth after a long cold stretch can push animals to eat what they would otherwise skip.

Some plants are dangerous at one growth stage and harmless at another. Some stay toxic in hay. Others are only a problem after frost, drought stress or herbicide treatment changes the plant. Because of that, a plant list alone is not enough. You need to know the conditions that turn a weed into a threat.

Learn your pastures before you need to

Walk every pasture at least once each growing season with a notebook or phone. Look along fence lines, ditches, ponds, woodlots, old homesites and disturbed ground, because poisonous plants often start in those edges and spread inward.

Take clear photos of anything you cannot name and bring them to your county extension office or a range specialist. Many offices will identify plants from photos and can tell you which ones are a known concern in your region.

• Mark problem patches on a simple farm map
• Photograph plants at flowering and at seedling stage
• Note which fields had trouble in past seasons
• Check hay fields and purchased hay for the same weeds

Reducing exposure through grazing management

Good grazing is the first line of defense. Pastures with a thick, healthy stand of desirable forage leave less room for weeds and give cattle something better to eat. Avoid turning hungry cattle into a field known to hold a toxic plant, and fill them with hay or good forage first.

Move cattle out before a pasture is grazed short. When animals are forced to eat everything, they eat the weeds too. If a patch is small and dangerous, fence it off until it can be dealt with.

Control methods and when to use them

Control options include mowing, hand removal, grazing management, competition from improved forage and herbicide. The right choice depends on the plant, the time of year and whether the plant is annual or perennial. Timing matters a great deal, and a treatment at the wrong stage can waste money or even make plants more palatable.

Treated plants can become more appealing to cattle for a time, and some remain toxic after they die. Keep animals off treated areas as long as the label and your extension specialist advise. Follow herbicide label directions exactly, and keep chemical records.

Hay, feed and cut forage

Poisonous weeds do not lose their danger when baled. Inspect hay as it comes off the truck, and break open a few bales rather than judging by the outside. Ask sellers what weeds are in their fields.

Keep a few flakes from questionable lots for identification if animals later get sick. Do not feed hay with heavy weed content to hungry cattle, and consider mixing it with clean hay or testing it with your nutritionist's help.

If you suspect poisoning

Sudden death, staggering, tremors, drooling, bloating, trouble breathing or several animals sick at once calls for an immediate phone call to your veterinarian. Move cattle away from the suspect pasture or feed, but handle animals calmly because stress can make some cases worse.

Do not try home treatments. Write down what the cattle ate, when they were moved, how many are affected and what the weather has been like. Remember that any animal that is treated carries a withdrawal period for meat, and that label or veterinarian directions must be followed exactly to protect the beef supply.

• Common mistake: assuming a plant is safe because cattle grazed it last year
• Common mistake: spraying and turning cattle back in too soon
• Common mistake: ignoring weeds in hay

Records and special situations

Write down where and when problems occurred, what the weather was doing, and which plants were present. Over a few years those notes show patterns, such as a particular fence line that gets trouble after a dry summer or a hay source that keeps bringing in the same weed.

Share what you learn with neighbors and the extension office. Poisonous plants do not respect property lines, and a regional picture helps everyone. Teach hired help and family members to recognize the main problem plants on your place so more eyes are watching.

Cattle that have just been hauled, weaned or moved to unfamiliar pasture are at higher risk. They are hungry, curious and unfamiliar with the plants around them. Offer good hay or forage on arrival and watch them closely for the first days. Stressed or thin cattle also tend to graze harder and farther. Keep body condition in mind, because a well-fed herd is more likely to leave unpalatable plants alone.

• Keep a pasture map with problem areas marked
• Log treatment dates and label restrictions
• Save photos from each growing season

More in Nutrition, Forage & Grazing

• Pasture Renovation Basics
• Fencing for Rotational Grazing
• Water Placement and Grazing Distribution
• Managed Intensive Grazing
• Drought Feeding Plans
• Feeding Cattle During Drought