Chinese Pistache Problem - please help

[bil...@mindspring.com]

I live in Dallas Texas, and have 3 of these trees. One has many leaves
turning yellow/brown with little black spots. We have had a drought
situation, but this is only occurring on about half of the tree. Is this
symptom always a fungus, and how do you spray a tree that is 20' high if it
is?

[dd]

If it's thousands of tiny spots...more like pin pricks...you may have
spider mites, which are an opportunistic pest thet is most difficult
during hot, dry, dusty weather, especially if the trees are stressed from
lack of water. Treatment is with a product called Pentac, which (unlike
other, less effective treatments) is supposed to be harmless to bees,
which are in a shocking decline across the country as it is.

If the spots are larger than a pin-prick, you may have sunscorch, and no
amount of spraying will fix that. But good, deep watering, administered
only when soil is beginning to dry... not every day, will cause
unblemished new growth to emerge (provided you fertilized adequately).

In both cases, old, damaged leaves wont lose the damaged spots, but you
should leave them to help the tree continue to make food from the sun.

Black, wet-looking spots could be caused by fungal or bacterial problems,
but it seems the less likely possibility: both fungi and bacteria need
either outright wet conditions, of extremely humid air to sprout their
spores on leaves. Neither event applies to dry and dusty Texas this year.
The only way this possibility could apply, is if you water constantly from
above, which seems unlikely, since we are talking about a tree, not
bushes.

David Deutsch
Gondwana Gardens
http://www.gondwana.org

[bil...@mindspring.com]

From what you said, I think I will try good deep watering first (on the days
that I can). From where it sits, between two streets, it gets the least
water from our sprinklers. For the last 7 weeks, that has been the only
source of water. I realize the spots won't go away, but I can watch to see
if it takes over the tree. I know two other Chinese Pistache trees down the
street from me have died, and so I want to take care of it before it's too
late.

If that doesn't work - I'll try the mite treatment. There are thousands of
spots, however, they range in size from pin pricks to irregular quarter inch
diameter spots, so it doesn't sound like mites are the problem.

Thanks so much for the help!

Becky

dd wrote in message ...