[6] Feeding causes leaves to show chlorotic stippling (light coloured marks from lack of chlorophyll) near leaf veins which can spread across the entire leaf causing them to lighten or bronze, ultimately leading to premature falling.

[2] In 2006, outbreaks were discovered by agents from the Plant Health and Seeds Inspectorate (PHSI) at two nurseries in Bedfordshire[10] along with a stand of plane trees nearby.

[9] After the adults have mated, the female lays eggs on the undersides of leaves of the host tree, usually near a fork in the veins.

When the eggs hatch, the juveniles stay close together at first, only moving onto a new leaf at the fourth instar stage.

[6] The insects are restricted to the underside of the leaves where little black mounds of dried frass can be seen and the shed skins of the nymphs often adhere to the leaf.

Overwintering generally takes place as adults in crevices or under flakes of bark, the insects being able to withstand temperatures down to at least −24 °C (−11 °F).