1Most likely
Mealybugs
Sap-sucking scale insects that hide in leaf joints and under leaves, protected by a waxy white coating that looks like small tufts of cotton. They excrete honeydew, a sticky, sugary residue that coats lower leaves and attracts sooty mold.
Tell-tale sign
White, cotton-like clusters tucked into the angle where a leaf meets the stem, often with a sticky film on leaves below.
60-second check
Touch one of the cottony spots with a cotton swab dipped in rubbing alcohol. If it's a mealybug, it'll turn brown and fall apart instantly.