River birch leaf damage - Ask Extension
Hi, I planted a river birch last fall. The leaf is showing symptoms of disease. What should I do? Thank you! Ana
Knowledgebase
River birch leaf damage #830824
Asked May 18, 2023, 7:03 PM EDT
Hi, I planted a river birch last fall. The leaf is showing symptoms of disease. What should I do? Thank you! Ana
Montgomery County Maryland
Expert Response
This is the abnormal (but unconcerning) tissue swelling (gall) caused by a tiny sucking insect called aphids. (This particular type of aphid is called the spiny witchhazel gall aphid).
Natural predators like lady beetles help to keep this aphid in check, particularly if you don't use broad-spectrum insecticides in your landscape. You can see them in action here:
https://extension.umd.edu/resource/spiny-witchhazel-gall-aphid-images
It's interesting and important to recognize the larval stage of ladybugs (they resemble alligators imo) so that you don't inadvertently kill them:
https://extension.umd.edu/resource/ladybird-beetles-or-ladybugs
Christine
Natural predators like lady beetles help to keep this aphid in check, particularly if you don't use broad-spectrum insecticides in your landscape. You can see them in action here:
https://extension.umd.edu/resource/spiny-witchhazel-gall-aphid-images
It's interesting and important to recognize the larval stage of ladybugs (they resemble alligators imo) so that you don't inadvertently kill them:
https://extension.umd.edu/resource/ladybird-beetles-or-ladybugs
Christine
