Gall wasp invasion infecting white oak trees in Missouri

Conservation officials ask Lake of the Ozarks property owners not to cut down their white oak trees despite the spread of disease. The jumping oak gall wasp spread its larva heavily in the area between Jefferson City and Rolla this spring, infecting white oak trees.
Signs of jumping gall disease are easily visible on fallen leaves.
“Close examination shows pinhead-sized buttons on leaf bottoms. These bumps eventually turn brown and fall to the ground where they commence bouncing, as if they were alive,” Missouri Department of Conservation News Services Coordinator Jim Low explained.
The galls, abnormal growths on leaves caused by wasp larva, cause leaves to jump and bounce when the larva move. The galls cause the white oak leaves to fall from the tree and appear brown and dead. As a result, property owners often mistake the disease for a tree’s death in early summer.
“Experts say the galls rarely cause significant damage to trees. They are just one of life’s irritations for healthy oak trees, sort of like fleas on a rabbit,” Low said.
Even with the unsightly infection, trees can still convert carbon monoxide into oxygen and continue living.
“Galls generally cause little real damage. Infested leaves, which can be twisted or curled up, are usually able to carry out photosynthesis at near-normal levels,” Bruce A. Barrett of the University of Missouri Extension Division of Plant Sciences said.
Barrett estimates that there are 1,500 species that produce galls on trees and plants. Most gall-producers are insects and mites. The galls can form in all sorts of shapes depending on what insect larva produces them.
Less noticeable galls on small branches, twigs, and roots and cause health problems for trees over time. In order to lessen the risk to trees infected with jumping galls, the MDC recommends that property owners maintain good growing conditions for trees. Regular watering during dry periods, spring fertilization, and the removal of fallen leaves help lessen the impact of galls.
Trees with existing damage run greater risk of being one of the statistical few to die from jumping gall disease.
“Oaks that have fungal infections or have suffered extensive limb loss due to ice or wind already are stressed. For these trees, the demands of replacing dead leaves can lead to long-term declines in health,” Low said.