Forest Insect and Disease Newsletter

Update on bur oak blight

image: Bur Oak list of CountiesAs of the end of 2011, bur oak blight (BOB) was diagnosed from 14 more counties, bringing the current total number of counties with BOB to 20. The disease, thought to be native, is found in a scattered pattern that spans the entire state from north to south and east to west borders. We suspect the increase in counties is due to a combination of factors: outreach and increased awareness of BOB, more folks looking for and reporting symptoms, and free sample analysis at the University of Minnesota Plant Diagnostic Clinic if it is the first BOB diagnosis in the county.

image: Bur oak blight.

As survey efforts continue, we anticipate that BOB will be confirmed in many additional counties since the range of bur oak encompasses the entire state.

Another important point to add to this discussion is that Dr. Harrington, Iowa State, feels that BOB is not only just a newly identified disease, but that it is likely a native disease. "Recent genetic analysis reveals a significant level of genetic variation that strongly suggests that the fungus is a native disease. Its distribution coincides with the distribution of the small-acorn variety of bur oak, Quercus macrocarpa var. oliviformis. Unusually wet springs for the last 20 years may be the most important contributing factor for the relatively recent prominence and recognition of this disease."

More information:

It looks like bur oak blight (BOB) really isn't new.- written by Dr. Harrington.