Spotted locoweed

Spotted locoweed (Astragalus lentiginosus) is a perennial herbaceous plant belonging to the Fabaceae family. While it is a natural part of some ecosystems, in agricultural settings, it is classified as a significant weed, particularly on rangelands and grazing areas where it poses a risk to animal health and land productivity.

The plant is commonly found in the arid and semi-arid regions, thriving in various soil types including sandy and rocky substrates. It often colonizes overgrazed or degraded pastures, where the reduction in native vegetation cover allows the weed to establish itself. Once established, it can spread rapidly, displacing forage species and reducing the overall carrying capacity of the land.

The biology of the plant is defined by its remarkable adaptability to drought. It features a deep taproot system that ensures survival during dry seasons. The plant reproduces via seeds, which are produced in distinct, often inflated pods. These seeds exhibit dormancy, meaning they can persist in the soil seed bank for years, making long-term control a challenging task for land managers.

The primary economic and agricultural impact of this species is its toxicity. It contains swainsonine, an alkaloid that causes a condition known as «locoism» in cattle, sheep, and horses. Affected animals exhibit erratic behavior, loss of weight, reproductive failure, and neurological damage, which can lead to significant economic losses for livestock producers.

Effective control measures require a combination of strategies. Mechanical control, such as grubbing or timely mowing before seed set, can reduce population growth. Chemical control using systemic herbicides is also common, but must be applied carefully to target the plant during its active growth stage. Integrated pest management, focusing on restoring healthy forage cover, is the most sustainable approach to long-term control.

• Grubbing individual plants before flowering.
• Selective herbicide application for dense infestations.
• Managing grazing pressure to prevent overgrazing.
• Reseeding desirable forage species to increase competition.