Storing Blackspot

I was going to post here asking about how to store blackspot so that it could be used to inoculate seedlings in the spring and get a quicker evaluation.

I keep coming back to Bill Radler…everyone seems to say that his roses are the cleanest and David told me that Bill inoculated his seedlings with blackspot.

Then I stumbled on the following article about Radler and I thought I’d share it:

The paragraph that caught my attention was this one:

“William collects diseased leaves early in the season and dries them on sheets of newspaper. The dried leaves are put into a kitchen blender to create a powder. Large quantities of this powder are sprinkled over the entire rose garden while the rose leaves are wet. The overhead watering adds additional moisture and creates an ideal environment for infection.”

It goes on to say that symptoms usually appear in two weeks.

This is great! I wonder if I can keep the blackspot leaf powder overwinter in the freezer. I think I am going to try.

I spent some time a while back going through the scientific literature on blackspot, and yes, it looks like it is routinely stored for several years in the freezer without a loss of viability.

To successfully inoculate, water is critical – liquid water in the leaf surface is required for blackspot to germinate and infect the leaf.

Joe, check your yahoo email for some papers I’m sending along.