The larvae are transparent or white and narrowly cylindrical, with the final (third) instar reaching a length of 15 to 20 mm (0.6 to 0.8 in).

The insects emerge from pupation in early summer and the female searches out a suitable host tree, usually Betula pendula or B. pubescens.

The larvae emerge near the base of the tree in the late summer or early autumn, fall to the ground and pupate in the plant litter or soil, where they overwinter.

[2] When choosing where to lay eggs, the adult female P. betulae probes twigs in the upper part of the crown of host trees with its ovipositor and tends to select vigorous young shoots.

Once the tree reaches around thirty years of age its growth rate slows and infections diminish.