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Plant Diseases/White fungus on Crown of Thorns


Same as above
Same as above  
Crown of Thorns
Crown of Thorns  
I have a blooming CoT that I've had for almost a year. I live in the San Francisco area. The plant spent all last summer on my covered deck with afternoon sun. I brought it in this winter and it gets south sun. It has had blooms on it all this time but I have noticed recently that it is getting white powder spots where the blooms come off the throne stem. and also on the sticky stalks of the individual blooms. It wipes right off but is hard to reach next to the thorns. I have been watering it once a week but maybe that's to much. What else could be causing this and what do you recommend I use to get rid of it? The image I have isn't very clear but I hope it will be helpful.
thank you,

ANSWER: Carol:
Unfortunately, your images are too "fuzzy" to give me much information.  Can you try again? Suggest that you review your images on your computer to be sure they are in focus first.  Take a few images, then check their clarity before sending.  Getting an accurate identification is the first step in controlling the pest.

These cottony growths may be a type of insect such as wooly aphids or mealybugs.  You are welcome to send a couple more photos and you may wish to "Google" images of these two insects to compare with your plants. These insects make their living by sucking the juices from plants.  They have many predators while outside, but when they are brought in, there are no predators so the insects flourish without any enemies.


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White powdery stuff
White powdery stuff  

White powdery stuff
White powdery stuff  
QUESTION: Hi Steve, I think these are better pictures.
Thank you,

Hi Carol:

I believe these "tufts" of cotton-like material is an insect rather than a disease. As mentioned earlier, these are either woolly aphids or mealybugs (type of scale insect).  If you have a few of these on your plant, you can dab them individually with a Q-tip soaked in rubbing alcohol.  There are some effective insecticides that you can spray with if the numbers are real great on the plant.  See your local garden center or nursery for the most effective ones to use and are safe on COT.  See "Google Images" also.


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Dr Stephen Vann


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


Plant Diseases Identification and Management

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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