Thought this might be of interest. Article is about the fungus that caused the Irish Potato Famine spreading across the US. I’ve been seeing this kind of damage on roses, too, alas, and been wondering what it was. Oh well, time to get out the spray…
Link: www.sciencedaily.com/releases/2009/07/090701163647.htm
Downy mildew seems to be lingering. While the optimal germination seems to be approx. 65 degrees, it shows low sporangium germination at approx. 35-45 degrees, and at least in California (maybe we have a super strain) ‘isolates germinate as high as 77 degrees’. We have had so much (like either every day or every night since the 1st of May, and sometimes both) of these temps, coupled with high humidity, that even the Inez Grant Parker rose garden in Balboa park is inundated with Downy mildew. And I am still finding many publicly displayed for sale roses with Downy. And just received 2 mini’s(among others) about a month ago with a full blown Downy attack through the mail from a California retailer. Since you are seeing fungus in Co., is this happening in other places? I have picked out several photos recently posted that I swear have downy. The good thing is, I believe I have about 10-15 seedlings that have proven themselves Downy resistant. Organic sprays just don’t work that well against it, and it is having a detrimental effect on hip set with certain roses. Jackie