The brown spots are from some sort of chemicals you have used on your leaves.

The white is very common for end of summer lilacs and in fact can only be avoided by treating with an anti-fungus sort of spray in the beginning stages.

Just make sure that once the leaves drop for the season, you rake good and catch it early next year, before it takes hold.

Mike

Hmm... I don't really use chemicals on the leaves, though I did put down some anti-weed stuff on the grass some weeks ago. I was careful to keep it off the lilacs.

By the way, I posted a link to this discussion in the shrubs forum, and there was a general belief that I had planted far too close to the house. Do you agree?

Hi Newhomeowner. I wish I knew your real name:-0)

I have been growing Lilacs for years and have had them up even closer to my home. They are impossible to burn unless something accidently got sprayed on them or from frost damage.

In fact, I think they will love that spot. They will flourish from the lime leached from the cement and will not be bothered by your home. If anything, they will learn to grow away from your house.

I have been doing some searching for you and found nothing that looks like the leaves on yours.

I'll link you to images to see if you recognize anything. I hope this helps. Good luck with them. I hope this was only a fluke thing for you.

http://images.search.yahoo.com/search/images?_adv_prop=image&fr=aaplw&sz=all&va=lilac+diseases

Mike

Thanks, Mike. Well you know, I'm hearing that since these lilacs grow so large, they may cause damage. See http://forums2.gardenweb.com/forums/load/shrubs/msg091924433130.html?10 What do you think?

I'll be happy to move them in the spring, if that's best, or not, so I'd be curious to get your view on the discussion.