mildew on rhodo
leaves of our rhododendron are not looking good. They have gone
white, as if they have powdery mildew. What should I do?
varieties of rhododendrons and azaleas are more susceptible to powdery
mildew than others. I have heard yellow ones tend to be worse than
others, but how badly any variety is affected will depend on your
local weather conditions.
The disease is usually
at its worst during warm, humid, summer weather. You can't control
the weather, so the next best thing is to spray your plant with
a fungicide, such as Super Sulphur, Bravo or Fungus & Mildew Spray.
Ideally spray in spring
to protect new growth before disease symptoms appear, then again
later in the season when conditions favour the disease, and in autumn
to reduce the number of disease spores which can overwinter to cause
problems again the following season. Mix the spray according to
the label recommendations.
Some gardeners have had
success reducing mildew problems by thoroughly spraying the foliage
with a solution of liquid seaweed fertiliser, so that could be worth
a try, too.
Gardener, Issue 173, 2005, Page 28
Reproduced with permission from the former Weekend Gardener magazine. The views expressed here are not necessarily those of the RNZIH.