Question: what are the white spots on my hydrangea leaves?
Answer: Answer. This is mysterious. Most fungal diseases found on hydrangeas cause leaf spotting on the foliage rather than the stems, so I suspect that the white spots could be the eggs of a sap-sucking scale insect called Pulvinaria hydrangeae, or hydrangea scale. This limpet-like insect also feeds on acers and cherries.