Why Are The Topmost Leaves Of My Adenium Plant Turning Yellow Then Brown?

Question

It had happened once before but I just pruned the top branch off, hoping it would go away. I also observed that the leaves at the bottom were turning yellowish green. The underside of the leaves also seems to have small black dots, I think they’re just dirt since they easily came off when I brushed the leaves, but I’m not so sure about it. Also, The topmost leaves suddenly fell as I was checking the underside of the leaves. I live in a tropical country and it’s usually 27°~32°C (or about 80°~90°F) in here.

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Answer 1

Your desert rose could use a few treatments with neem oil and/or insecticidal soap. Here's info on the soap:
https://www.gardeningknowhow.com/plant-problems/pests/pesticides/homemade-soap-spray.htm
and here's more general information on the plants and their requirements:
https://www.gardeningknowhow.com/ornamental/flowers/desert-rose