The longer I live in Florida, the more I’ve become aware of the growing problem of scale insects. Would you believe that there are more than 7,500 species of these parasites, and most homeowners don’t even know they exist until such a large population develops on their plants that they’re difficult to control.
There are two main groups of scales:
Soft scales – which secrete honeydew, much like aphids, and often herded like cattle by ants.
Armored scale – which unlike soft scale, doesn’t secrete honeydew but instead inject their waste back into the plant resulting in the plant developing poor vigor and death if a large enough population of armored scale is present.
While numerous pesticides (especially imidacloprid) claim to control soft scale, they have no effect on armored scale, which is best treated with systemic insecticides such as dinotefuran or clothianidin; which works on both groups.
For me, the best thing a homeowner can do is monitor your plants (particularly camellias, pines, sago), and if you find scale, treat immediately with appropriate pesticide. Be sure to cover the entire plant including upper and lower leaf surfaces, stems/trunks, and applying a soil drench when required. Keeping the scale population to a minimum is the best control.