Alatae emerge from the 3rd generation onwards and enventually breed on Galium . Apterous migrants are attended by several species of ants , which protect them from predators such as ladybirds , hoverflies and various hymenopterous insects. Winged sexuparae appear in early September and return to pear. Aphids produce considerable quantities of honeydew , thus causing a scorching of leaves which, moreover, become covered with sooty moulds . Growth is suddenly interrupted.
Unaffected leaves remain normal. .
On a petiole and a leaf. Growth of terminal bud is arrested. .