Beans
Mesquite (Prosopis glandulosa)

Description
Mesquite is a small to medium height tree or shrub that is thorny and branching near the ground or single stemmed. The leaves are alternately located along the stems, deciduous, and dark green in color after maturity. The fruits are loosely clustered pods (beans) up to 8 or 10 inches in length and may be abnormally abundant in some years.

Distribution and Habitat
Mesquite is generally found throughout Texas but common on dry ranges and in washes and draws at low elevations in the Trans-Pecos region. It is especially common along streams and where the water table is high. It is found from California to Texas, Kansas and Mexico.
Regions: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10.

Toxic Agent
Cattle primarily are affected by mesquite beans, although goats are also known to be affected. Sheep are reported to be resistant. The biochemical pathology of mesquite poisoning is only partially understood. In some ways the syndrome produced by a diet of mesquite is best considered a nutritional problem. Mesquite beans have a high sugar content which, together with inadequacy in other dietary factors, alters rumen microflora, inhibiting cellulose digestion and possibly contributing to rumen stasis and impaction. B vitamin synthesis is inhibited. Ketosis may follow in severe cases or in pregnant animals.

Livestock Symptoms
The chronic form of the disease, jaw and tongue trouble, develops gradually, usually after cattle have been eating beans for 2 months or more. They gradually become emaciated and may lose 50 percent of their weight. Afflicted cattle salivate profusely and chew continuously, sometimes without anything in their mouths, and will hold their heads to one side as if chewing were painful. About 25 percent of affected animals have a partial paralysis of the tongue, which protrudes from the mouth 1 to 4 inches. At least 10 percent of poisoned animals will have swelling under their jaws or tongue, and some will have enlarged salivary glands. Signs of acute poisoning may include:

• loss of appetite
• rapid loss of weight
• nervousness
• a wild expression
• bulging eyes
• death

Integrated Management Strategies
Most cases of acute poisoning occur in pastures where large quantities of mesquite beans accumulate such as where pack rats store them. Cattle should not be allowed to consume large quantities of beans for more than 60 days without adequate high quality roughage. A combination stocking of cattle and sheep will reduce cattle losses, since sheep are apparently not affected by the beans. If the disease has not progressed too far, three out of four animals will survive if given high quality ground feed and rumen inoculation with fresh rumen fluid.

Numerous control methods are available for mesquite. The plant is rarely controlled solely because of its toxicological implications, but because it competes for moisture and space and can greatly reduce the growth of desirable forage. In severe infestations, plant density can impede other management activities as well.

Long-term mesquite control usually requires a variety of control and follow-up techniques. These may include ground or aerial broadcast chemical control, mechanical methods (grubbing, root plowing, etc.), individual plant treatments, and prescribed fire.

A Tactical Brush Management System (TBMS) focuses on preventive control measures, targeting the smaller, younger mesquites with individual plant treatments (chemical or mechanical) and/or fire. This system can reduce overall herbicide usage and expense and can also be used as a follow-up treatment after large scale control measures. Chemical control recommendations for mesquite are numerous and specific. For specific herbicides and rates refer to Extension publication B-1466, "Chemical Weed and Brush Control Suggestions for Rangeland."

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