Identifying Large White Grubs at the Base of a Tree

A homeowner discovered numerous white, ribbed larvae—about five inches long and as thick as a marker—at the base of a tree that had died and needed removal. Concerned about the identity of these "worms" and whether they posed a threat to other trees, they sought expert advice.

The larvae are most likely the immature stage of a large beetle, such as a rhinoceros beetle or Hercules beetle. These grubs feed on decaying wood and fungi within dead or dying trees, not on living tissue. Their presence indicates the tree was already in decline from other causes—such as disease, root damage, or environmental stress—before the beetles moved in. The grubs themselves do not kill healthy trees.

For reference, the University of Kentucky's Critter Files provides a description and images of Hercules beetle larvae: Hercules Beetle Larvae.

Since these insects only colonize dead or dying wood, they will not spread to healthy trees. No treatment is necessary. Focus instead on identifying what caused the original tree's decline—consider soil conditions, drainage, recent construction, or disease—and address those factors to protect remaining trees.