I sure hope you get that under control in a hurry. What a shame to see this. I went out in my garden right away to-day after seeing this just to see if I have any thing going on. So far so good. I had this problem a few years ago. What ever you do do not let water splash around this stuff it will spread the mildew like crazy
Well, I have never had mildew on apple tree or gooseberry plants before, so I went out and pruned out any effected growth, which wasnt much. So fingers crossed it doesnt spread.