Here you can request to determine the cause of the damage. You can view the requests of other users and sort them according to the selected criteria. In addition, you can get information about your request, and you can follow the progress of its current state. If your application was not approved, it had probably been because it was impossible to identify the damage based on the sent photos or because the application does not address our topic - determining the pests of trees and shrubs. We will inform you about the status of your application by email.
Hi Tina, than you for your requestt. This is caused by Andricus quercuscalicis, a small wasp species. It's called a Knopper gall. The female wasp lays her eggs on the acorn cup in May and injects a special fluid into it. In response, the oak tree forms a strange growth – a green, irregular lump about 2 cm long, known as a gall. Inside this gall, the wasp larva develops. With best regards Milan Zubrik
One can see the little larva if we cut the galle in the middle
Answer
Dear Marie, thank you for your inquiry. This is a gall caused by the small hymenopteran species Andricus quercuscalicis, known as the Knopper gall. The female of this small wasp lays eggs on the acorn cup in May, injecting a special liquid inside. As a result, the oak forms a specific neoplasm — a very irregular, approximately 2 cm long, green lump (gall) — in which the larva develops. The gall seems to overgrow the acorn cup and sometimes even absorbs the entire acorn. This prevents the acorn from developing normally and causes it to lose its ability to germinate. It can damage up to 70-80% of the harvest in localized areas. Damaged acorns fall off prematurely. With best regards, M. Zubrik
