Disease Du Jour (July 12)

To get the week off to a good start our “disease du jour” comes to us courtesy of Russell Harris in Orleans parish. This is oak leaf blister caused by the fungus Taphrina caerulescens. The disease develops on a wide variety of oaks and is seen here on a water oak (Quercus nigra). The blisters typically bulge upward with a depression visible on the lower surface of the leaf. Initially, the blisters may be whitish or light green, but as they age the tissue dies and becomes brown, as seen here. The pathogen attacks the young, expanding leaves when temperatures are mild and there is plenty of moisture to keep the foliage wet. Once the leaves are fully expanded, they become resistant to disease. When disease is severe, it may cause some defoliation, but this does not generally affect the overall health of the tree. Fungicides applied prior to bud break and during early leaf development may aid in the control of this disease, but spraying large trees in residential neighborhoods is generally problematic.  

Leaf blister on water oak.

Advertisements

About Don Ferrin

I am an associate professor and extension specialist in the Department of Plant Patholgy & Crop Physiology with the LSU AgCenter in Baton Rouge. I have statewide responsibility for issues and educational programs related to diseases of all horticultural crops in Louisiana.
This entry was posted in Forestry / Urban Forestry, Ornamentals and tagged , , , , , , , , , , , , , . Bookmark the permalink.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s