What grows on live tree leaves?

dwheeler at teleport.com dwheeler at teleport.com
Sun Sep 14 02:51:37 EST 1997

In article <5vc2e1$dbi at ccshst05.cs.uoguelph.ca>,
  pjf at uoguelph.ca wrote:
> In this area, in late summer, I notice some trees have lower leaves that
> are covered in "white powder".  I suspect control is next to impossible
> (Collecting and disposing of fallen leaves may slow it down).  Are there
> many species involved (I see maple, lillac, and others infected)?  The
> affected tree seem to be doing fairly well (haven't died yet).
> --
>  /PJ   "You can't grep dead trees"  pjf at uoguelph.ca  (519)824-4120x6309

The key to your post may be where the fungi occurs. Powdery mildew is
common where overwatering occurs on foliage. Your post notes "the lower
leaves" are involved. For trees, this may mean a sprinkling system nearby
which also hits these lower branches.

In Oregon, I often have this problem with flowering plants, especially
lupine and gloriosa daisy. It is easily solved by careful water only at
the base of the plant.

I understand this fungus may also be spread by aphids. If this were the
case, more than just the lower leaves would be involved.

It is probably too late to do anything about the fungus this year.
However, adjustaing any nearby sprinklers to spray at lower levels may
aid next year's foliage without applying fungicides, which can kill the
mycorrhizal fungi necessary for the tree's health, and thus should be

Daniel B. Wheeler

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