The Verdict - Buckthorn Disease is Oat Crown Rust

I received a number of responses and all led me to Oat Crown Rust as the disease that has affected our buckthorn bushes. Some bushes are so badly hit now that they appear to be dying, or at least severely weakened.

Thanks to Drs. Andre, Bernard and Richard.

Richard Wilson,  Forest Program Pathologist with the Ontario Ministry of Natural Resources provided the following response.

 I am pretty sure what you are seeing is Oat Crown Rust, and buckthorn is the alternate host for this disease. This is a tentative identification for now and I will send you positive ID once our lab can confirm this.

The causal agent of this disease is Puccinia coronata, a serious disease on oats and as you have seen, can be very damaging to buckthorn too.  I have include a few websites here for your information.

http://ipm.illinois.edu/diseases/series100/rpd109/

http://www.apsnet.org/publications/imageresources/Pages/Volume87-8-1-3.aspx

http://www.omafra.gov.on.ca/english/crops/facts/ontweeds/european_buckthorn.htm



I now see the rust affecting buckthorn quite widely for many kilometres all around.