Verticillium wilt on Japanese maple

A Japanese maple branch that turns brown and dies suddenly in late spring or summer -- while the rest of the tree looks fine -- is the classic presentation of Verticillium wilt on a woody plant. The disease is unpredictable. Some trees lose a single branch and carry on for decades. Others decline.

A Japanese maple branch that turns brown and dies suddenly in late spring or summer — while the rest of the tree looks fine — is the classic presentation of Verticillium wilt on a woody plant. The disease is unpredictable. Some trees lose a single branch and carry on for decades. Others decline over two or three seasons and die. There is no cure, no spray, and no fertilizer that reverses the infection once the vascular system is colonized.

I don't grow Japanese maple in my Long Island garden, but the disease is common enough in zone 7a that I've seen it in neighbors' yards, always following the same branch-flagging pattern. This guide draws on University Extension and botanical garden research.

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The pathogen and host susceptibility

Verticillium wilt on Japanese maple is caused by Verticillium dahliae and, less commonly, V. albo-atrum. Per Missouri Botanical Garden, Acer palmatum (Japanese maple) is highly susceptible to V. dahliae, one of the most susceptible ornamental trees.

The same pathogen infects tomatoes, strawberries, eggplant, and dozens of other vegetable and ornamental hosts. Per UC IPM, more than 300 plant species are susceptible. This wide host range means V. dahliae can persist in a planting site indefinitely when a rotation of susceptible hosts is maintained.