Dutch elm disease
Ophiostoma ulmi
dutch elm disease
Image provided by Joseph O'Brien, USDA Forest Service, U.S.
Plant hosts
  • Major hosts: Ulmus alata (winged elm), Ulmus americana (american elm), Ulmus glabra (mountain elm), Ulmus laevis (russian white elm), Ulmus minor (european field elm), Ulmus procera (english elm), Ulmus rubra (slippery elm), Ulmus serotina (red elm), Ulmus thomasii (rock elm), Zelkova carpinifolia (caucasian elm)

Means of movement and dispersal
 
Plant parts liable to carry the pest in trade and transport:
  • Bark: Spores, hyphae and fruit bodies are born internally and externally. Spores, hyphae and fruit bodies are invisible.
  • Growing medium accompanying plants: Spores are born externally and are invisible.
  • Leaves: Spores are born internally and are invisible.
  • Seedlings and micropropagated plants: Spores and hyphae are born internally and are invisible.
  • Roots: Spores, and hyphae are born internally and are invisible.
  • Stems: Spores, hyphae,and fruit bodies are born internally. Spores, hyphae and fruit bodies are invisible.
  • Wood: Spores, hyphae and fruit bodies are born internally and externally. Spores, hyphae and fruit bodies are invisible.
Plant parts not known to carry the pest in trade and transport:
  • Bulbs, tubers, corms, rhizomes and fruits.
  • Flowers.
  • Seeds including grain.

Symptoms
 
Early symptoms are wilting leaves and sparse foliage, first on single limbs but later the entire tree may be affected. Yellowing and premature defoliation follows. Symptoms may show only a few days after infection has occurred. If infection is high in the tree and late in the year, disease progress may be slow. If main limbs are infected through lower branches in spring, progress may be rapid, and the tree can wilt and die in a short time. These symptoms may be confused with other vascular wilt diseases or summer heat stress. Infected sapwood shows brown streaking especially in its current season growth. A cross-section often shows either a broken or continuous brown ring in outer growth rings.
 
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