Subject: Re: Moldy lilac
From: "Bill Robinson" <roseguy@flash.net>
Organization: Flashnet Communications, http://www.flash.net
Date: 31 Aug 1997 22:35:50 GMT
Message-ID: <MOD$970831.22211@rec.gardens.ecosystems>
References: <MOD$970831.13930@rec.gardens.ecosystems> <MOD$970831.19987@rec.gardens.ecosystems>



> Nancy Wright wrote:
> >
> > Would appreciate insights into white mold suddenly covering an otherwise
> > healthy four-year-old lilac bush. It's been a strange season of weather
> > here in Michigan: a cold, wet spring followed by a cool, cloudy summer.
In response, Severin wrote:

> You have whats commonly known as powdery mildew. There are plenty
> of fungicides on the market to combat the problem. I would suggest
> trying one and maybe some selective pruning to the affected plant . At
> the base of the plant try removing some of the older branches but not to
> many for this will lower your blooms for next year. The purpose of prun
> ing is to allow more air and light to come through the plant .. Mildew
> starts when the leaves stay damp for long periods of time and the spores
> start growing on the leaves.

It is difficult to say with certainty that the "white mold" is powdery
mildew. If
a lilac is going to come down with a "white mold" it is usually downey
mildew
which is a different disease. Powdery mildew needs a dry surface to become
attached and to thrive. Downey mildew needs a wet surface. Powder mildew
likes warm temperatures, Downey mildew likes it cool. My hunch is that you
more likely have have downey mildew but you asked about treatment.

Virtually all of the commercial fungicides work to prevent the spread of
the disease
and are of little value in correcting an established infection. Virtually
all of the
commercial fungicides are toxic to the soil mycorrhizae and they should be
avoided in the home garden.

I'd go along with Severin's suggestion of pruning. Remove all of the
foliage that
shows any signs of mildew, rake up around the base of your infected plant
and
remove all plant debris, put that stuff in a plastic bag, seal it shut, and
throw it
in the garbage - not your compost. Do some pruning to open up the bottom
structure
to let in more sun and more light. Add a 2"-3" layer of clean compost under
your
infected plant. Work at keeping the foliage dry.

The primary goal is to keep the disease contained. It can and will spread.
Keep an eye
on that infected plant. The infection shows up on the bottom leaf surface.
Get that infected
stuff out of your garden. If the weather turns hot and dry, the problem
may self-correct.
If you continue to have cool and humid weather, the downey mildew will go
from bad to
worse. If things start getting out of control, you should probably spray
with a smothering
oil like Eco-Oil from Garden's Alive. It is relatively safe to use and it
has very little
impact on the environment.

There really are alternatives to the use of synthetic fungicides in the
garden.

Bill