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PLEASE NOTE:
"Poisonous" does not mean deadly. Some manifestations of toxicity are subtle. The dose, as always, determines if a plant is safe source of nutrients or a toxic hazard.

Control of Astragalus and prevention of poisoning

Astragalus caryocarpus or Ground Plum from Pammel

Animals become conditioned to feeding on Astragalus and others around them "learn" to eat it as well. Many ranchers know that if they have a small number of animals in their herd that begin to eat locoweed, soon the majority of the herd will begin to eat. According to a number of studies done, grazers normally do not have a preference for eating Astragali because it is not very palatable but, through one animal beginning to eat it, others will follow. This phenomenon is known as "social facilitation" -or- peer pressure. Animals that have become addicted will continue to eat locoweed until they die.

Due to this addiction or habituated preference for locoweed, it is important to have no animals in the herd which are Astragalus eaters. They will "teach" other animals in the herd to eat it, thereby causing the poisoning of the majority of the animals. (Ralphs et al. 1990, Ralphs et al. 1994)

Ueckert (1984) described pesticide measures for clearing land of Astragalus mollisimus. These are necessary at times when the threat of animals eating and becoming habituated to the plants are high.

  • foliar sprays of 2,4D from October through April at a rate of 1.1 kg/ha
  • foliar sprays of Picloram at a rate of 0.2 - 1.1 kg/ha in fall or winter

It was also found that fall applications were the most effective and that most other seasons had a lower rate of success.

Astragalus alopecuroides from The Illustrated Encyclopedia of Horticulture

Locoweeds have growth habits that make poisoning more likely. They remain green over the winter and are often the first plants to begin regrowth in the spring, making them a suitable feed for animals during the time when few other plants are available. In order to avoid this, ranchers should not overstaock ranges that have an appreciable number of locoweeds in them, allowing for enough good forage so animals don't begin to graze on the locoweed. By keeping locoweed free plots for spring grazing and animals that have become habituated to locoweed, poisoning can be minimized. Animals should also be watched closely for signs of poisoning and removed to "clean" pastures should they begin to show symptoms of poisoning. Clean pastures can be made through the use of pesticides or determined weeding (sometimes very difficult because of the deep root of Astragali). (Ralphs and Pfister, ! 1994) Less hazardous pastures can also be made by early season clipping of Astragalus. This results in there being smaller amounts of edible biomass and lower overall amounts of toxins. (Majak et al. 1988)

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