Oak trees can be plagued by a number of insect pests. These insects tend to feed mostly off an oak's leaves though some will eat actual oak wood. Common leaf-eating pests include the gypsy moth, the Oak leaftier and the forest tent caterpillar. The Formosan termite, which can be found in parts of the Deep South and in a small area in California, attacks and feeds off the wood in live oak trees.
Leaf-eating pests on an oak are the most common of the insects that may come to infest the tree. The gypsy moth is a voracious feeder on an oak's leaf. Males are greyish brown and fly. Females are large, whitish and can't fly. Oak leaftiers are small, bell-shaped and yellow with a violet to brown front wing. The forest tent caterpillar has a brownish body with lines along its sides which are blue in colour.
The Formosan termite is a voracious eater of oaks that tends to create very large colonies within the tree. They attack these and other species of tree with great enthusiasm. Like ants, they're also divided into subspecies types, including soldiers and workers. All eat wood, and soldier termites are aggressive, attacking anything or anyone that moves toward them. Most Formosan termites are yellowish-brown or off-white in colour and about a 1/2 inch in length.
Methods for ridding an oak tree of an insect infestation will depend on whether the insects are leaf eaters or Formosan termites. In the case of former, you should be able to apply commercially available insecticides yourself. Also, if they're leaf eaters, killing them when they are in their egg or larval stages is recommended. Formosan termite eradication when in a live oak, though, is extremely difficult and usually involves eventually cutting down the tree.
Natural solutions to the gypsy moth issue involve a substance that can be sprayed on the very young insects. Bacillus thuringiensis, or B.t., is a bacterium that works well to kill the moth after it has emerged from its egg. For caterpillars, a wide band of sticky tape coated with a horticultural pest barrier and placed around the tree's trunk about chest high has proven effective. All are organic in nature and are safe for humans.