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House Plants/black spots under croton leaves


My croton is about 5 years old and was repotted several months ago when the soil started smelling like rotting soil.I don't know the species. I may have used a soil that I used for the yard and it had some compost in it. I used a high grade indoor house plant soil this time. It did amazingly well for quite awhile and then one day I noticed that there were tiny black spots mostly on the underside of the leaves. I believe it is spreading when the sides of the leaves rest on other leaves.I wiped down the plant thoroughly with a wet paper towel- the speckles wiped off and left a purplish color on the towel. I have now wiped it down thoroughly twice and it is a lot better but it is still a problem and the leaves are definitley showing stress now.

Hi Jessica,

From your somewhat limited description, I believe the black spots are scale insects. Scales have soft bodies that are covered by a hard protective shell. They don't move or look like other insects, but they are. Wiping will remove the visible scale insects, but it invariably misses the translucent juveniles that hide in tiny crevices.

Mix a solution of 5 parts water, 1 part rubbing (isopropyl) alcohol and a squirt of liquid dish soap. Then, spray that solution so that all leaf and stem surfaces on your Croton are dripping wet. This is a messy process but it is the only way to get to all of the scale insects. If you are thorough, one treatment is usually successful, but you should be watchful for any future reappearances of the scale.

Insect infestations are often an indicator of other problems because insects thrive on plants that are under stress for other reasons. In your case, I am concerned about the repotting, which should not have been done and was not done properly. Outside garden soil and compost should never be used. And there is no such thing as "high grade indoor plant soil."

Unnecessary repotting often leads to root rot. I cannot be sure if that is the case with your Croton because I do not have the details of what you did. However, you must be very careful not over water your Croton and make sure it is on a sunny windowsill.

I have written detailed articles on treating pests, repotting and on Croton care that I will email for free to you (or anyone else) who emails a request to me at I have also written an indoor plant care book in a PDF format that I can sell you if you contact me at my email address.

Please let me know if any of this is unclear or if you have any additional questions.

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Will Creed


I am the only expert in this category with professional hands-on experience and knowledge of all indoor plants. I can answer questions regarding light, water, fertilizer, repotting, pruning and humidity and temperature requirements. I can identify plant pests and provide information on safe, effective treatments. My answers are based on 35 years of professional experience and scientific research and are clear and easy to understand. I do NOT use search engines to find answers to your questions. If you read my previous posts here, you will get a good idea as to how thorough and professional my answers are.


I have over 35 years of professional indoor landscaping experience caring for plants in homes, offices, building lobbies, stores, restaurants, and other adverse environments. I have written extensively on the care of indoor plants, including a 260 page book. My specialties include Ficus trees, low light plants, repotting, pest control, and re-blooming holiday plants. Be sure to check my ratings and nominations to learn why I am the top-rated indoor plant expert. I am the only House Plant expert consistently ranked in the AllExperts Top 20.

BA, Amherst College

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