Weevil response from the Royal Horticultural Society
The beetles are a species of leaf weevil (Phyllobius or Polydrusus species). These beetles are found during late spring and early summer when they feed on the foliage of a wide range of deciduous trees. They can cause a significant amount of damage to the foliage during late spring if they are numerous. They lay their eggs in the soil and the larval stages feed on the roots of grasses and they are not regarded as being a pest when they are at that stage in their life cycle. They are not easy to control! Adult leaf weevils can be controlled on plants that are small enough to be sprayed but any reduction in their numbers may be short-lived. This is because the adult beetles fly readily during warm weather and so you may find more weevils moving onto your plants from other gardens. Fortunately, the damage caused by these weevils is limited to a few months during the spring and early summer, so the damage does not go on throughout the growing season. Adult beetles tend to be relatively tolerant of pesticides because they have a hard body shell that insecticides do not readily penetrate. Plants that are being attacked by leaf weevils can be sprayed with -:
acetamiprid (Scotts Bug Clear Ultra Gun!)
deltamethrin (Bayer Sprayday Greenfly Killer)
lambda cyhalothrin (Westland Plant Rescue Fruit & Vegetable Bug Killer)
imidacloprid (Bayer Provado Ultimate Bug Killer)
pyrethrum (Py Spray Garden Insect Killer or Scotts Bug Clear Gun for Fruit & Veg)
thiacloprid (Bayer Provado Ultimate Bug Killer Ready to Use or Bayer Provado Ultimate Bug Killer Concentrate 2).