Which invasive plant is toxic to cattle and horses?

Cytisus scoparius, commonly known as Scotch broom, is the correct answer as it is recognized for its toxicity to cattle and horses. This invasive plant contains toxic alkaloids that can cause significant health issues in livestock if ingested. Animals may suffer from symptoms such as gastrointestinal distress and, in severe cases, it can lead to more serious health complications.

Scotch broom is prevalent in disturbed areas and can form dense thickets, which may limit grazing opportunities for livestock and contribute to its invasive nature. Understanding the toxicity of this plant helps in managing its spread and protecting livestock health in agricultural and pastoral settings.

The other plants listed, while they may have negative impacts on ecosystems or agricultural practices, do not share the same level of toxicity to cattle and horses as Scotch broom does. The knowledge of such toxic plants is essential for effective management in right-of-way and agricultural practices.