Certified Arborist Practice Test

The correct answer encompasses all the organisms listed—bacteria, fungi, and viruses—because each type can contribute to vascular diseases in trees.

Bacteria are known to cause vascular infections that often lead to wilting, necrosis, and eventually tree death. These pathogens can block water and nutrient transport, leading to significant health decline in affected trees.

Fungi are particularly notorious for causing a range of vascular diseases. They can invade and obstruct the xylem, which is responsible for transporting water and nutrients. Fungal infections can also produce toxins that further damage the vascular system.

Viruses can also play a role in vascular diseases, though their effects might manifest differently compared to bacteria and fungi. Viral infections can impair plant growth and development, altering physiological functions, which may indirectly affect the vascular system.

Understanding that all three types of pathogens can cause vascular diseases highlights the complexity of tree health and the need for comprehensive management strategies to address these threats effectively.