Knowledgebase
Stem Gall/Rough Bullet Solution? #869891
Asked May 24, 2024, 9:24 AM EDT
I have a young quercus bicolor with a moderate to heavy infestation of stem gall oak/ rough bullet galls.
1. Is there any permanent solution to the infestation short of removing the tree or will any treatment fall short of a long term solution and the galls will always return or be present? ( I have tried a systemic in the fall and foliar spray in the spring with some result, but there is still a noticeable amount of leaf damage and the wasps have emerged flying around the tree. It seems like treatment will be a never ending battle where there will always be an infestation to address.)
2. If removal is the only long-term solution, may I immediately replant with a tree not desired by the galls or should I wait a certain amount of time for the pests life cycle to complete without the host present to end the cycle?
3. If I need to wait to replant, will covering the area with black plastic for a certain amount of time kill off any of the in-ground life cycle pests quicker than having to wait for them to emerge and not have a host?
Thank you!
Baltimore County Maryland
Expert Response
Treatments aren't usually necessary or recommended for these galls. The tiny wasps that cause them are well protected in the gall structures and so pesticides are not very effective on them. That said, we know that the honeydew sections of the galls can attract nuisance insects like yellowjackets. Depending on the placement of the tree, you may simply try to avoid the area when wasps are most active. It's up to you about removal of the tree -- but swamp white oaks are a known host of these galls (as are other white oaks) and these trees provide a variety of benefits in the environment. The gall wasps don't spend any portion of their lifecycle in the ground, so covering it with black plastic will not have an impact. This page from entomologist Whitney Cranshaw provides further information about their life cycle and notes that spring foliar sprays and soil injections have not been effective.
Christa
