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Rose Bush
Q: Hello Tom. We have a long standing rose bush, but last year and now again the
leaves are yellowing with dark spots. I am afraid I will lose all the
leaves and lose the rose bush itself.
Your thoughts much appreciated.
A: Wet spring conditions are favorable to leaf fungi, and it sounds like
you have the infamous black spot that roses get. Since this is a fungal
disorder, so you'll need to do spray or dust applications to control it.
A visit to your local garden supply center should do the trick.
Describe the symptoms, tell them you have a preliminary diagnosis of black
spot (you might want to take in a leaf or two to show them), and ask them to
show you the various control products they have.
There are many products available that control leaf fungi, either in
liquid or dust form. Dusts you simply apply by, well, dusting the foliage
with the material straight out of the box. The downside to dusts is that
they wash off easily, so when you water you must be careful not to wet the
leaves. You would also want to dust after a rain.
Liquids usually have a greater residual on the leaf. Some come prepared
to spray right out of the bottle, others you dilute to the correct strength
and apply with a hose-end sprayer.
Whatever product you choose, ALWAYS follow the label instructions for
dilution rates and application techniques. More chemical does not mean
better control. Sometimes it even reduces the effectiveness, so apply only
the correct amount per the label's directions.
You shouldn't lose the rose to this disease, but it will make the rose
look pretty tired. Dispose of fallen infected leaves regularly, and next
year start with the control applications early in spring so that the disease
doesn't get too far ahead of you.
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