Why are some pine cones in my park extremely sappy?

The resin (sap) production generally occurs due to wounds created on the developing cones. The most common wounding agents are seed and cone insects that feed on these structures. Damage from these insects can be prevented with properly timed insecticide applications to the developing cone during the summer months. This is seldom warranted except in seed orchards where genetically improved pines are grown for seed production to produce superior seedlings.