mildew on oaks
you tell me what's wrong with my young oak trees? They started off
healthy in spring, but now all the leaves have a white coating and
they've stopped growing.
mildew is the culprit. There are different powdery mildews - some
attack a range of plants, while others only affect one or two particular
The problem usually starts
in warm humid weather in spring or early summer and continues to
get worse through the rest of summer. When the autumn rains arrive
it's usually less of a problem, but by then the damage is done,
with the affected leaves often falling off early.
You can't do much to
change the weather or stop the fungal spores drifting in on the
wind, but the disease won't kill your young trees - although it
might slow them down a bit.
If you do want to take
some action, you could spray with a fungicide such as Fungus Fighter
or Fungus & Mildew Spray. Or you could try a weekly spray of one
teaspoonful of baking soda dissolved in one litre of water with
a couple of drops of dishwashing liquid added, or organic sprays
such as Nature's Way Fungus Spray or Super Sulphur.
Gardener, Issue 143, 2004, Page 26
Reproduced with permission from the former Weekend Gardener magazine. The views expressed here are not necessarily those of the RNZIH.