My two mature apple trees suffer huge attacks from woolly aphids. The insects seem to survive cold winters, emerging to colonise the trees in late srping. Insecticides based on thiacloprid, deltamethrin and even acetamiprid (intended for ornamentals only) seem just to encourage the aphids, either by acting as aphrodisiacs of killing competing orgabisms. The trees, formerly productive, are being seriously damaged. Any suggestions?
- 20 Mar, 2011