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Oh what is that on my beautiful roses?


Blackspot is a plant disease caused by a fungus (Diplocarpon rosae) that is a source of major problems. If you are growing roses in Florida you will see a lot of blackspot if you aren't on a regular spray schedule. There are a few roses that aren't troubled by blackspot. Mostly Old Garden Roses and a few shrub roses.

Blackspot looks like circular black spots with irregular edges on the top side of the leaves. The tissue around the spots or the entire leaf turns yellow and the infected leaf will fall off. Plants with a severe case may lose all of their leaves if not treated. Flower production is often at a minimum and the quality of bloom suffers badly.

The high humidity here in Florida causes the spores to germinate. They can be air borne or on splashing water. It is fine to wash your bushes by spraying them early in the morning so the leaves can dry before dark it is important the the leaves do not stay wet over night as this causes the spores to germinate.

Control with Dithane M-45 and Funginex applied every 7 days follow label directions for mixing  and be sure to water roses well the day before spraying. Blackspot is not cured but prevented.




page updated: Monday, September 02, 2002