To be sure I'm
continuing with the copper oxychloride and have started spraying with
insecitcide.
[/nag mode on/]This is the problem with treating a problem without
knowing what's wrong: You're using at least one unnecessary
pesticide. Nowadays the EPA has stopped worrying about individual
exposures to individual pesticides, and is concentrating on figuring
out the effect of lifetime exposure to all pesticides. You should
try to minimize your overall exposure. [/nag mode off/]
Woolly aphids are furry white lumps. They will scrape off with your
finger, and if squished, will bleed aphid blood. They are hard to
treat with insecticides because their "wool" is hydrophobic. Summer
oils will work, but these tend to be phytotoxic to maples. If it
were my maple, I'd scrape off the adults by hand, and treat
periodically with a contact insecticide like a pyrethrin to catch the
"crawlers" (immature, thin-skinned stage).
Spider mites, if they reach really high levels, will cause extensive
webbing on the underside of leaves. But it doesn't look like powder:
it looks like webs. Washing the leaves with a hard stream of water
periodically will usually get rid of them; if not, pyrethrin sprays
will.
Powdery mildew generally causes white powdery spots on leaves. It is
only mildly harmful to trees unless they are being kept in bad
conditions with poor air circulation. Part-sun and good circulation
will solve the problem better than a fungicide.[And you have to
believe me on this, because I am one of the US's powdery mildew
experts. Once in a while I actually know what I'm talking about].
Let us know if you figure out what the maple actually has: If you
want to cut to the chase, take the tree to your nearest county
Cooperative Extension office, and they'll be able to give you a
positive ID. Good Luck!
--
Nina Shishkoff
Frederick, MD
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