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- Metropolitan Forestry Services

General Description:

Jumping Oak Gall refers to a species of parasitic wasp (Neuroterus spp.); a very small non-stinging insect. These wasps cause small bumps (galls) to form on the undersides of leaves. Each gall contains a larva where
the insect begins its life cycle.
Research shows that the gall is relatively harmless on healthy trees. The presence of small populations should not be of major concern. Trees under stress from drought, flooding, other insects, or construction damage are most at risk for attack.

Susceptible Species:

White Oak mostly, however other Oaks in the White Oak group may become targets as well.

Identification:

Signs of the Jumping Oak Gall can first be spotted in late spring as leaves can be spotted with brown, button-like bumps on the undersides of its leaves. The leaves may brown up and fall off by early summer. Once on the ground the tiny galls are reported as to ‘jump’ as the larvae vigorously moves inside. New wasps emerge from the galls the following spring.

Symptoms:

A browning of White Oak tree tops in late spring which may fall to the ground by early to mid-summer. The problem may persist for a few years but like many insect populations usually fades after natural predators and conditions control the infestation. Other studies show that Oaks respond for several years after insect infestations by increasing the tannin content in their wood and leaves, this is a naturally produced insect deterrent.
Prevention and Treatment: Chemical control usually is usually not warranted as the insect is not a major problem on healthy trees. Also because of its life cycle timing it is difficult to target for proper treatment. As always the best treatment is PREVENTION. Keep trees free from stress (drought, nutrient deficiencies, soil compaction, mechanical damage, etc…). Good sanitation by raking up and removing or composting infested leaves should alleviate some future infestations.

For a pdf factsheet of this factsheet: Jumping Oak Gall

Our goal is to provide you with the best possible service. If you are not satisfied with any treatment or completed job, we will resolve the situation to your satisfaction. We want to do our utmost to ensure your trees and shrubs are always 'green and growing'.

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