Spots on Oak Leaves - Ask Extension
We have two small oak trees and both of them have spots on the leaves. From the underside of the leaf, it is a raised creating a little bump. What i...
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Spots on Oak Leaves #647410
Asked June 07, 2020, 3:06 PM EDT
We have two small oak trees and both of them have spots on the leaves. From the underside of the leaf, it is a raised creating a little bump. What is causing it and will it damage the trees? Is there some something that should be done?
Benton County Oregon
Expert Response
Hi;
Seems both of those images are of the top of the leaf. I am imagining the little granule on the bottom side of the leaf. Those seed-like grains are galls formed by a tiny insect larvae. They are one type of 5 or 6 that we can find on our OR white oak. These are called Jumping galls.
Jumping oak galls cause small yellow spots on the upper surface of infested leaves. On the underside of the leaves are tiny seed like galls. These appear in midsummer or later. Inside each gall is the larvae of a tiny wasp. In the fall, the galls drop from the leaves to the ground, where the activity of the larva causes the gall to jump an inch or more off the ground. The wasps overwinter in the galls on the ground. In the spring, emerging females lay eggs in opening oak buds. Adult females emerging from these galls lay eggs on the leaves, producing the larvae which cause the jumping oak galls. Although they may be unsightly, jumping oak galls do relatively little damage.
https://pnwhandbooks.org/node/6971/print
Look closely and you might find some others like speckled galls (poppers) or apple galls.
They are all co-evolved, relatively harmless and for many people, fun to observe.
Seems both of those images are of the top of the leaf. I am imagining the little granule on the bottom side of the leaf. Those seed-like grains are galls formed by a tiny insect larvae. They are one type of 5 or 6 that we can find on our OR white oak. These are called Jumping galls.
Jumping oak galls cause small yellow spots on the upper surface of infested leaves. On the underside of the leaves are tiny seed like galls. These appear in midsummer or later. Inside each gall is the larvae of a tiny wasp. In the fall, the galls drop from the leaves to the ground, where the activity of the larva causes the gall to jump an inch or more off the ground. The wasps overwinter in the galls on the ground. In the spring, emerging females lay eggs in opening oak buds. Adult females emerging from these galls lay eggs on the leaves, producing the larvae which cause the jumping oak galls. Although they may be unsightly, jumping oak galls do relatively little damage.
https://pnwhandbooks.org/node/6971/print
Look closely and you might find some others like speckled galls (poppers) or apple galls.
They are all co-evolved, relatively harmless and for many people, fun to observe.
Thanks Brad, that looks exactly like what we have. I appreciate your time and advice. Kent
