Insect pests like forest tent caterpillar and spongy moth (Lymantria dispar) and diseases like oak wilt may become more active and damaging in oak forests under a warmer climate.

Under a high emissions scenario, researchers forecast more insect pest damage in northern forests due to increased metabolic activity in active periods and increased winter survival. Drought-stressed trees are also typically more vulnerable to insect pests and diseases. New pests such as Asian longhorn beetle present unknown risks. Stressed forests may also be more susceptible to oak wilt and oak decline.