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Plant Diseases/Black discoloration on peony flowers, but healthy leaves

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Blackening peony flower
Blackening peony flowe  

Blackening peony flower
Blackening peony flowe  
Greetings Dr. Vann,

I am seeing a problem with a client's peonies that I have never seen before. Some of her flowers are healthy, but other are turning black and shrunken. I suspect that the condition can be treated with a preventative, but I do not know what I would be preventing. I have grown peonies for years and have never seen this. Can you help me to diagnose it, and find a preventative?

Thank you.

Answer
Donna:
A couple of possibilities-- Look for a very tiny insect called thrips.  Check carefully within the petals for these 1-2 mm length yellowish cream critters.  Spread the petals apart slowly to look down inside the bloom to the areas of petal attachment.  Beware that they can move very fast!

Another possibility is a fungus disease called gray mold.  It is caused by the organism called Botrytis.  Stick one or two of the affected blooms in a Ziploc plastic bag with a wet paper towel resting beneath the blooms. Seal it and wait 48 hrs then look at the bloom outside of the bag.  If gray mold is the culprit, you will see a gray "fuzzy" growth on the bloom.  There are a few effective fungicides that are effective.

Regards
steve

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Dr Stephen Vann

Expertise

Plant Diseases and Disorders of Lawn Grasses, Trees, Vegetables,and Ornamentals

Experience

Plant Diseases Identification and Management

Education/Credentials
B.S. Botany --- Miss. State Univ. M.S. Plant Pathology --- Miss. State Univ. Ph.D. Plant Pathology --- Texas A & M Univ.

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