In a nutshell: The only surefire cure is to throw the affected plants away. The whole story: Scales suck. These nasty little insects pierce your plants with their mouthparts and literally suck out sap from your plants' stems and leaves. They also excrete a sticky substance called honeydew, which encourages the growth of a black fungus called sooty mold and leaves a mess on nearby floors and furniture. Many species of scale, including Coccus hesperidum, attack houseplants, especially ornamental figs (Ficus spp.). Young scale insects are called crawlers because they crawl to a feeding site, insert their mouthpieces, and settle in. They eventually lose their legs and antennae, develop a shell, and stay put for the rest of their lives. Once an insect develops its shell (or scale), it is very difficult to eliminate. The easiest way to get rid of scale is to throw out infested plants as soon as you notice a problem. If you want to save your plant, then you'll have to plan your battle carefully. First, isolate affected plants to prevent spreading the infestation. Then remove adult scales by pruning out heavily infested areas and scrubbing off all the remaining adults with a toothbrush and soapy water. Rinse the plant thoroughly and allow it to dry. Crawlers can be controlled with soap spray (Safer soap is one brand), but the soap must come in contact with the insects. Spray the plants once a week for at least a month, making sure to coat the stems and tops and bottoms of leaves. Keep watch for adults and scrub off any that appear. Continue this process until no adults or crawlers are detected for several weeks. Scales are attracted to lush foliage, so don't fertilize during the treatment period and keep watering to a minimum. If an infestation occurs during summer, place the plants outside and let their natural predators, including lady beetles and parasitic wasps (Microterys flavus and Metaphycus luteolus), help you control the problem. Before bringing your plant back inside, inspect it carefully. As an added precaution, you can spray it with a light all-season or summer horticultural oil to smother any remaining scale insects. Always examine houseplants before you buy them, and consider isolating new plants for one month while you observe them for problems.
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