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Horse Chestnut Scale

Horse chestnut scale, apparent as circular white spots on trunks or large branches (and sometimes mistaken for pigeon droppings), is caused by the insect Pulvinaria regalis.

This insect pest is occasionally found disfiguring trees in urban localities, roadside pavements or other hard surfaced areas such as patios. This insect has little effect on the health or vigour of plants, therefore it is not something that needs to be controlled.

This is fortunate, as many of its host plants are too large to be sprayed. On smaller trees in gardens it is feasible to brush or wipe the mature scales and their eggs from the stems in April to May to stop the next generation developing but on larger plants the scale has to be tolerated.