Succulent house plants with mystery problem

Asked September 21, 2018, 2:55 PM EDT

I have a large Jade plant and a couple of other smaller succulents with what I guessed might be scale. The problem was much worse earlier in the summer and when they were inside. I sprayed them twice with Neem, which cut back the infestation, but is still quite bad, particularly on the smaller succulents. I'm not sure if they're all in the Jade family but can definitely report that not all succulents seem to be affected.
Symptoms: leaves turn yellow and fall off; black spots very large with grey borders, almost looked as if you could scratch them off until 2 treatments with Neem decreased size to those in pictures. New healthy leaves keep forming, but then they get the black spots too.
I'm afraid that it will get worse again and maybe even spread to others when I bring everything back inside. I'd like to be able to treat them before then but obviously the time line is getting shorter.

Livingston County Michigan

3 Responses

Good afternoon,
Although there are several pesticides labeled for scale control, insecticidal soaps and horticulture summer and dormant oils are effective in controlling scale plus they are safer for you and beneficial insects. Generally multiple sprays ten to twelve days apart are needed. Dormant season oil sprays are effective for most scale except oyster shell scale and only partially effective for pine needle scale. Be sure to read and follow all label directions. Also, make sure you are not watering too much and never let water touch the leaves. Another thing to be sure to do is fertilize. Make sure the plants get fertilized and when outside do not sit plants sit in direct sun. I hope this helps with your plant problem so you can take them in and not spread this problem to any other house plants. Thank you for using Ask an Expert and good luck!

Thank you. I have some insecticidal soap, so will try that since it's one of the products you suggested. I see no way to apply it without getting water on the leaves though. I'm thinking you mean regular watering, not the treatment (or so I plan to proceed). Do you suggest I get rid of the plants if I can't clear whatever is going on? Also, I thought it might be scale, but diagnosis was really part of my question as I actually have no idea of what scale really looks like. Do my pictures look like scale?

Hello again, Yes, it is scale and another method of getting rid of them is to take a cotton swab and dab with alcohol and swab the leaves. And, I did mean not to actually get water on the leaves when weekly watering. Let me know if I can be of any more help. Thank you again for using Ask an Expert.