On large trees, predatory insects will often bring the aphid infestation under control. Boring insects are most likely to attack weakened or stressed trees. Newly planted young trees may also be attacked. No chemicals are available. Keep trees as healthy as possible with regular fertilization and water during dry weather.
Caterpillars feed on oak.
Large trees tolerate some feeding injury without harm. Trees repeatedly attacked, or having some other problem, may need spraying. Tent caterpillars form nests in trees then eat the foliage. The nests can be pruned out when small. Chemical controls for tent caterpillar are Orthene, Diazinon, malathion, or methoxychlor.