Japanese Beetles and Leafhoppers
The primary insect that will bother young apple trees is the Japanese Beetle. These beetles usually do not appear until mid to late June and they can last up to six weeks. Sometimes caterpillars can be a problem, but Japanese Beetles are the main threat for a young tree. Generally a tree can lose 25% of its leaves with very little effect on the healt of the tree. But the beetles will not stop until the trees are sprayed. One can apply Sevin or Malathion. Imidan is another very good insecticide that will kill the beetles, but it may be harder to locate. Do not spray Sevin more than 3 times a season as it could promote spider mites, another problem and another type of spray.
Leafhopper damage: only the top leaves have been affected. They have responded by curling.
Leafhoppers can also affect the growth of trees. These small insects (an adult is about 1 mm long) do not eat the leaves in the same way as the beetles, but they do feed on the leaves and can secrete a poison into the leaf making it curl and cause the tree to temporarily stop growing. Applying Sevin will also kill the leafhoppers.