Damage. These are pests which may be serious on top fruit and ornamentals, especially woody members of the Rosaceae family. The caterpillars eat away leaves in spring and early summer and often form other leaves into loose webs, reducing the plant's photosynthesis. They occasionally scar young apple fruit.
Life cycle. This pest's timing of life cycle stages is unusual. The pest emerges as the adult form from a soil-borne pupa in November and December. The male is a greyish-brown moth, 2.5 cm across its wings, while the female is wingless. The female crawls up the tree to lay 100200 light-green eggs around the buds. The eggs hatch in spring at bud burst to produce green larvae with faint white stripes. These larvae move in a characteristic looping fashion and when fully grown, descend on silk threads at the end of May before pupating in the soil until winter.
Spread is slow because the females do not have wings.
Control. A common control is a grease band wound around the main trunk of the tree in October which is effective in preventing the flightless female moth's progress up the tree. In large orchards, professional growers use springtime sprays of an insecticide such as deltamethrin to kill the young caterpillars.
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