The problem is likely Ips beetles. Ips beetles and other borers are serious pests of pines. These insects attack trees weakened by natural or manmade conditions such as drought, lightning, or construction damage. Both adults and larval Ips feed on the conductive tissues within the trunks of trees. Ips beetles also transmit bluestain fungi, which disrupt the water transport system of trees. Insecticide sprays applied to the trunk will probably not save an already infested tree. Spraying nearby uninfested trees with appropriate pesticides will help protect them from attack, but the best protection is to keep the pine healthy to avoid attack.

For more information on control of boring insects see this fact sheet:

http://edis.ifas.ufl.edu/mg007