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Sunday, March 1, 2015

Black Spot and Rust Not Common in Vegas Roses

Q. Here's the pic of what's going on with my roses.  What do you think?  Black spot or rust?

A.This was sent to me in July, 2014.
I really didn't see any black spot or rust in the picture. Black spot of roses have the typical "black spots" on the leaves and rust are pustules on the leaves that can be rubbed off with your fingers.
Both are more common during the spring, periods of high humidity and too much shade. Usually full sunlight, drip irrigation (no overhead irrigations), watering during early morning hours, fertilizing regularly and our dry conditions seldom lend itself to either disease here.
If you need to put on a preventive treatment on roses in the spring or fall, apply one of these treatments to the leaves: sulfur dust, Neem oil or compost tea.
The damage looks more like spider mites, drought or lack of fertilizer. Make sure roses have an organic surface mulch applied to the top of the soil that decomposes (wood chips), use drip irrigation, water early in the morning and are fertilize during the spring and fall months. 

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