Utah State University Extension
Sycamore scale feeds on foliage of London planetree and California sycamore in urbanized areas throughout Utah. The insect is difficult to see with the naked eye, so we rely on the primary symptom of yellow-to-brown leaf spots. If needed, the timing of treatment is at bud break and involves oil application and/or a soil-applied systemic insecticide.
Murray, Marion and Davis, Ryan, "Sycamore Scale (Stomacoccus platani)" (2021). All Current Publications. Paper 2230.