Which root disease is described as causing fading crowns, shortened leaders, reduced diameter growth, and brown or black staining in root sapwood, with a management buffer strip of 50 feet?

• A. Black stain root disease
• B. Armillaria
• C. Laminated root rot
• D. Dwarf mistletoe

Answer: (A)

The symptoms described—fading crowns, shortened leaders, reduced diameter growth, and brown or black staining in the root sapwood—point to black-stain root disease. The key clue is the distinctive sapwood discoloration in the roots, which occurs as the fungus colonizes root tissue and impairs the tree’s ability to take up water and nutrients. This decline in vigor leads to crown thinning and slower radial growth.

A common management measure is a 50-foot buffer strip around affected areas. The idea is to reduce contact between infected and healthy trees and limit the spread of the disease through root connections and vector activity, helping protect uninfected stands. In practice, controlling this disease also involves removing or thinning infected trees and avoiding planting highly susceptible species within the buffer.

Other root diseases have different signs: Armillaria often shows white mycelial mats under bark and honey-colored mushrooms, laminated root rot produces a laminated, dark decay in roots and lower stems, and dwarf mistletoe is a parasitic plant that causes witches’ brooms and growth suppression rather than root sapwood staining.