A member of the caltrop family, African rue is
a bright green, suc-culent, perennial herb growing from a woody
base. It is bushy, many branched and about 1 foot tall when
fully grown. The leaves are alternate, hairless and divided
into narrow segments. The flowers consist of five white petals
and are present from April to September, with seed pods developing
in May to October.
Distribution and habitat
African rue is native to the deserts of Africa and southern
Asia. First recognized in the United States in 1935 on a section
of land near Deming, NM, it has since spread onto dry rangelands
in Arizona, southern New Mexico and western Texas. Regions:
7, 8,
10.
Toxic agent
African rue, which contains at least four poisonous alkaloids,
is toxic to cattle, sheep and probably horses. The seeds and
fruit of the plant are the most toxic; a lethal dose is 0.15
percent of the animal’s body weight. Young leaves are somewhat
less toxic than seeds, with a lethal dose of about 1.0 percent
of the animal’s weight, while mature leaves are less toxic.
Dry leaves are apparently nontoxic.
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Livestock
signs
Signs of chronic poisoning include:
• Loss of appetite
• Listlessness
• Weakness of the hind legs
• Knuckling of the fetlock joints Acute conditions
produce these signs:
• Stiffness
• Trembling
• Incoordination
• Frequent urination The body temperature
of poisoned animals is usually subnormal. They salivate excessively,
wetting the lower jaw and muzzle. Postmortem examination may
reveal hemorrhages on the heart or liver. Acute poisoning
usually is caused by eating seeds.
Integrated management strategies
African rue is extremely unpalatable. Animals eat it only
if they are starved or suffering from severe mineral deficiencies.
If poisoning occurs, it is usually in spring and summer.
When possible, avoid pastures infested with African rue
during these times. Remove livestock known to be grazing
young leaves or seeds of African rue from the area. If given
good-quality feed and water, chronic poisoning cases generally
recover. Chemical control treatments for African rue should
target problem areas such as roadsides, livestock pens and
traps, and areas around oil fields.
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