What causes my indoor Ficus tree leaves to get very sticky?
Stickiness on Ficus trees is caused by either scale insects or mealybugs. Scale insects appear as tan colored, slightly raised bumps about the size of match heads on the undersides of leaves and along stems. They rub off easily with a fingernail. Mealybugs look like tiny bits of white cotton on stems and leaves. Neither insect pest looks like a bug so they are often overlooked. Although mealybugs and scale insects look very different, they are close relatives and are treated in the same manner.
The mistake that most folks make in treating these pests is treating only the ones that are visible. The juveniles pests are nearly indivisible, so they are often overlooked. They will survive, reproduce and the problem will come back to haunt you. The key to successful treatment is spraying all leaves and stems until they are dripping wet. It is a messy process and is best done outside, but not in the direct sun.
Mix a solution of 5 parts water, 1 part rubbing (isopropyl) alcohol and a squirt of liquid dish soap in a spray bottle. Thoroughly spray this solution on all leaf and stem surfaces of the tree until those parts are dripping wet. Complete coverage is most important. If you are thorough, one treatment is all that is required.