I am wondering what causes scale on house plants. The plants I have that get scale are not near other plants. Only certain plants get scale, and others are not affected. There are a number of scale insects that infest house plants.
Some scales prefer certain plant species.
This suitable place may be the same plant they were hatched on or on adjacent plants. Once at these sites, they will settle down and begin feeding. The primary way scales get to new plants is by walking across leaves and table surfaces to new plants. They can also be spread if they get on your clothing. Males are capable of developing wings, and thus are able to fly to other plants that have crawlers which matured into females.