Scale are tiny sucking insects that damage plants by sucking the liquid from plant tissue. If left unchecked, the leaves will yellow and the plant will ultimately die. Scale insects are small oval shaped raised dots on the underside of plant leaves. They are difficult to notice unless you are looking for them. The scale releases a honeydew secretion onto the plant. This honeydew causes a reaction that turns into sooty mold, a black fungus. Discolored leaves and stems are indicative of scale.