Noxious Weed Identification

Noxious Weed ID Newsletter

Cody Trimble – January 2019

As we come into a new year we continue to deal with noxious and invasive species of weeds in our range and pasture land.  Over the next year I plan working with producers across the county to help better understand how to identify these species and eradicate them.  We will start with some identification tips and better understanding the effects of these weeds.  If you would like to be put on the email list to get this information be let know of dates of workshops, field days, and result demonstrations please sign-up below.

ANR - Email List

Email list sign-up for ANR.

African Rue

According to Toxic Plants of Texas, African rue is a member of the caltrop family, bright green, succulent, and a perennial herb growing from a woody base.  It is bushy, many branched, and about one foot tall when fully grown.  It originated in the deserts of Africa and southern Asia and has since made its way to the dry rangelands of Arizona, southern New Mexico, and western Texas.

African rue contains at least four poisonous alkaloids toxic to cattle, sheep, and likely horses.  Seeds are the most toxic at a lethal dose of .15% of the animal’s body weight.  Young leaves are lethal at 1% of the animal’s weight, while mature leaves are less toxic and dry leaves are apparently nontoxic.

Signs of chronic poisoning include loss of appetite, listlessness, weakness of the hind legs, and knuckling of the fetlock joints.  Acute conditions are stiffness, trembling, incoordination, and frequent urination.  Body temperature of poisoned animals is usually subnormal.  They tend to salivate excessively.

Animals usually only eat African rue if starved or suffering from severe mineral deficiencies.  Poisoning usually occurs in the spring and summer so avoid infected pastures during these times. Given good feed and water chronic poisoning case generally recover.

Perennial Broomweed, Broom Snakeweed

Based on information from Plants of Texas Rangelands this is a perennial half-shrub from 6 inches to 2 feet tall.  Unbranched, erect stems originate from a woody base and die back when the plan goes dormant.  Leaves are narrow and threadlike and small yellow flowers are clustered at the branch tips from June to October.

Perennial broomweed is widespread from California to Texas and Mexico to Idaho.  It poisons cattle, sheep, goats, and swine.  It is most toxic at early growth stages in late winter and early spring and on sandy soils.  Cattle abort after eating as little as 20 pounds of fresh broomweed in 7 days.  Cattle, sheep and goats have died by eating 10 to 20 percent of their body weight in 2 weeks.

Chronic poisoning signs are abortion, stillbirth, retained placenta, and weak offspring.  Acute poisoning signs are periodic thick nasal discharge, crusting and sloughing of the skin of the muzzle, listlessness, loss of appetite and weight, rough hair coat, and occasionally dark brown or reddish urine.  Frequent urination with diarrhea in the early stages to constipation with large amounts of mucous are also signs of poisoning.  Pregnant cows often have periodic vulvar swellings and premature udder development.

Russian Thistle, Tumbleweed

Toxic Plants of Texas describes tumbleweed as a many branched, annual herb growing to 2 to 6 feet tall.  At maturity it is stiff, prickly, round and bushy.  Spine-tipped leaves are oval and the stems have distinctive dark purplish striations when the plant is young and growing.

Tumbleweed is found in every region of Texas except the Piney Woods and Post Oak Savannah.  Nitrate is the toxic agent in the plant.  All ruminants are susceptible to poisoning, with cattle being poisoned most often.  Animals may die if they consume as little as .075% of their weight in nitrate.  Factors such as the plant growing in soils high in nitrate, excessive shade, lack of water, and stress or physical damage may also increase nitrate in the plant.

Acute poisoning often results in death with no previous signs of illness.  Less acute signs are weakness, unsteady gait, collapse, shallow and rapid breathing, rapid pulse, dilated pupils, recovery, delayed abortion, coma, and sudden death.  Unpigmented parts of the body like the whites of the eye, tongue and lips may have a blue-brown discoloration and blood may be a chocolate brown color.

Rayless Goldenrod, Jimmyweed

Described by Plants of Texas Rangelands as a low-growing half-shrub in the Sunflower family, rayless goldenrod has erect stems that arise from a woody crown and can grow 2 to 4 feet high.  Leaves are sticky, hairless, narrow, and located alternately along the stem.  It is often found on dry rangelands, especially in river valleys, drainage areas, irrigation canals, and on gypsiferous soil outcrops.

Goldenrod can poison all species of livestock and the toxic agent is tremetone.  Poison accumulates in the animal and is present in green and dry leaves, making it poisonous year-round.  The toxin can be passed through milk and it is common for poisoning signs to appear in suckling young but not the mother.  Lethal doses generally consist of 1 to 1.5% of the animal’s weight consumed over 2 to 3 weeks.

In cattle the plant produces trembles.  Muscular trembling is most noticeable about the nose, hips, and over the shoulders.  Stiffness and weakness are most pronounced in the forelegs.  In late stages the animal will lie down and not be able to get back up.  Other signs include vomiting, quickened and labored breathing and almost continuous dribbling of urine.  Shortly before death the animal breathes with prolonged inhalation followed by a pause and then a short, somewhat forcible expiration.


Comments are closed.