Disease

Bacterial leaf scorch

Xylella fastidiosa

A bacterium that lives in the water-conducting wood and is spread by leafhoppers and spittlebugs. It looks like drought scorch, but it comes back every summer on more branches. On a large oak, elm, sycamore, red maple or mulberry it takes 5 to 10 years to reach the whole crown, and the tree eventually dies.

Signs

• Leaf edges brown starting mid to late summer, with a yellow or reddish band between the brown and the green.
• Older leaves near the base of a branch scorch first.
• The same branches scorch every year, a few more each year, whatever the rainfall.

What favors it

Oak (pin, red, scarlet and bur), elm, sycamore, sweetgum, red maple and mulberry; heat and drought bring out the symptoms.

Prevention

• Plant nonhost or less susceptible trees where it is common on your street.
• Water deeply in dry spells and mulch the root zone; it may delay the scorch.

Crops it shows up on

Shade & ornamental trees.

Often confused with

Sources

• Bacterial Leaf Scorch of TreesUniversity of Maryland Extension
• SP661: Bacterial Leaf Scorch in Landscape TreesUniversity of Tennessee Extension
• Bacterial leaf scorchThe Morton Arboretum
• PPFS-OR-W-12: Bacterial Leaf ScorchUniversity of Kentucky Cooperative Extension

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