General Sherman Tree Health Inspection

Giant sequoia bark beetles (Phloeosinus punctatus) are native to California and feed on phloem sap in trees. This liquid contains nutrients and hormones generated through photosynthesis in the tree’s leaves. Giant sequoias are generally able to fend beetles off by exuding large amounts of the sticky sap to plug the beetles’ entrance holes and prevent entry into the pholem, a process known as a “pitch response.”

When trees are stressed from conditions such as multi-year droughts or overly-intense fires, they are no longer able to repel their attackers, and they can succumb to beetle infestations. The multi-year drought of the past decade, in combination with intense fires, is a vivid example. Many giant sequoias were no longer able to access water supplies they’d long relied upon; therefore, they were no longer able to generate enough pitch to close the beetle bore holes. This allowed the beetles to freely enter under the dead outer bark and reproduce there.

In 2017, researchers started seeing a small number giant sequoia trees in Sequoia National Park and other areas die from the combination of drought, fire, and bark beetle attack. When more giant sequoias started dying in subsequent years, the National Park Service could not ignore the threat. They could not risk harm to such a globally-important tree as the General Sherman, so they brought in Ancient Forest Society (AFS) to inspect it for damage from bark beetles and assess it’s overall health.