Dutch elm disease moves from diseased to healthy trees by which mechanisms?

Dutch elm disease moves from diseased to healthy trees by which mechanisms?

• A. Elm bark beetle feeding only
• B. Elm bark beetle feeding and through natural root grafts
• C. Wind-dispersed fungal spores only
• D. Soil movement of pathogens only

Answer: (B)

Dutch elm disease spreads between trees mainly through two pathways: elm bark beetles carrying fungal spores as they feed on and move through trees, inoculating healthy trees in the process; and natural root grafts that connect neighboring elm roots, allowing the fungus to move directly from an infected tree to a healthy one. So, beetle-mediated transmission plus root graft spread together account for how the disease moves. Wind-dispersed spores or soil movement aren’t the primary routes between trees, which is why those options don’t capture the real mechanism.

Dutch elm disease spreads between trees mainly through two pathways: elm bark beetles carrying fungal spores as they feed on and move through trees, inoculating healthy trees in the process; and natural root grafts that connect neighboring elm roots, allowing the fungus to move directly from an infected tree to a healthy one. So, beetle-mediated transmission plus root graft spread together account for how the disease moves. Wind-dispersed spores or soil movement aren’t the primary routes between trees, which is why those options don’t capture the real mechanism.