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Lilac > Stems/branches > Dead or dying branches

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Credit: M. Grabowski, University of Minnesota
Credit: Whitney Cranshaw, Colorado State Univ., Bugwood.org
Credit: Univeristy of Illinois
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Lilac Borer (also known as ash borer)
Podosesia syringae

Wilted or dead stems
Base of stem swollen with ¼ inch exit holes
Sap, sawdust and frass exuding from holes
Reddish-brown pupa cases sometimes found protruding from exit holes
Larvae are 1' long; creamy white with light brown head
Adult is a clear wing moth that resembles paper wasp; smoky brown forewing, hindwing is clear with brown edge.
More information on Lilac borer...

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Credit: M. Grabowski, University of Minnesota
Credit: M. Grabowski, University of Minnesota
Credit: M. Grabowski, University of Minnesota
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Witches' Broom
Candidatus Phytoplasma fraxini

Dense clusters of short, thin twigs originate from one area of stem
Leaves may be small, distorted and yellow
Brooms are common at the ends of branches and clustered at the very base of the plant
Entire canopy is pale green to yellow, some leaves with brown margins
Branches may die and shrub will decline
More information on Witches' Broom...

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Credit: M. Grabowski, University of Minnesota
Credit: W. Jacobi., Colorado State University, Bugwood.org
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Verticillium wilt
Verticillium dahlia

Leaves on one to several branches turn red to yellow, wilt, die and fall off
Dark olive to gray streaks are often visible in the sapwood if the bark is peeled back
The entire canopy may show symptoms in a single season or take several years
Symptoms are often most obvious in late summer and autumn but can occur throughout the growing season
More information on Verticillium wilt...

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