I have noticed lately that since I started misting my outdoor trees 3-6
times a day, some things are happening to some of the trees. Two dwarf
Myrtle have caught mildew fungus pretty badly, a flowering quince has
developed yelow and deformed leaves, a barberry has had it's blossoms
stop developing. There is an overall funk over a some of the plants.
Though, it has not affected the junipers. I live in zone 12 in the
desert, Tucson, humidity has been low, 15-25%. The dew point has been
24-30. Is there a point where there is too much water on the leaves and
top soil, or is it just learning which species like it and which species
do not? Brian
It's not clear to me why you're misting the trees. I mean, yeah,
you're in Arizona, but misting isn't helping to raise the relative
humidity to any significant degree, and *is* benefitting foliar
pathogens, so why do it? To increase humidity, put plants in an
environment that will encourage humidity without encouraging leaf
wetness. Erect a lathe roof to create partial shade. Screen plants
from drying winds.
The best thing to do about the powdery mildew (besides using a
fungicide) would be to increase air circulation. That will change
the microclimate of the leaves, making sure that microdroplets of
water evaporate as quickly as possible.
I don't know what's wrong with the quince: check for thrips, which
cause the symptoms you describe. Your quince is always going to have
problems; in hot climates, quince typically put out a burst of
flowers and leaves in the spring, then get blasted by the summer heat
and drop their leaves. They then reflower and re-leaf in the fall.
If you shade them during the summer, they should retain their leaves.
--
Nina Shishkoff
Frederick, MD
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