Forest pests including spongy moth (L. dispar) and southern pine beetle are already a serious threat to oaks and pines, and are expected to benefit from warmer and drier conditions. Drought stress may increase the risk of oak decline or sudden oak death.

Studies suggest that insect pests may increase due to increased metabolic activity in active periods and increased winter survival. Insect pests, such as spongy moth (Lymantria dispar) and southern pine beetle are expected to cause more frequent and severe damage under climate change, and new pests present unknown risks. Trees stressed by heat, drought, or disturbance are also typically more vulnerable to insect pests and diseases. Damage from existing native pests such as two-lined chestnut borer could combine with drought stress, for example.