Pest Alert: Bot Canker in Landscape Plants

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white oak canker

Flagging branch tips at the end of oak limbs is an indicator of Bot Canker in Oak

We have been seeing lots of Bot canker in landscape plants. Botryosphaeria is a fungus that causes a canker (infected wound) in oak, arborvitae, cherry laurel, Leyland cypress, and many other trees and shrubs. The fungus infects wounds on plants and kills the branch. Wounds can be caused by pruning, storm damage, cold damage, or excessive wetness.
bot canker wounds

Bot canker wounds cause the branch to swell eventually killing the branch.

There is no real treatment for the disease. Try to prevent damage to trees. Keep dwarf trees and shrubs as open as possible so that they will dry out after rain. Prune to allow air flow in plants. Clean out leaves from the insides of shrubs. Do not bury plants too deep in mulch. Prune out infected branches and fertilize affected trees if needed.
arborvitae with canker

We have seen many arborvitae with stem cankers due to piles of needles on the inside of the plants piling up and rotting wounding the wood.

dead arborvitae leaves

Clean dead leaves out of plants. Leaves pile up, rot, and damage stems leading to a wound that can be infected by fungi.