Dear Patty,

Thank you for reaching out to the UVM Master Gardener Program with your question.

Paper birch trees are susceptible to heat. We have had a warm and dry stretch of weather recently and the findings on your birch trees may be secondary to heat related stress. Drought symptoms can include wilting, curling of leaves and browning around the edges of the leaves. From the photos it appears that the findings are not isolated to a single limb or part of the tree. I am concerned that there may be more than one issue causing your trees’ findings. Stressed trees are more susceptible to other diseases/ pests. A common pest of birches is the birch leafminer. The timing of the onset of the findings in your birch trees would be consistent with the birch leafminer. The adults emerge in May and lay eggs on the leaves. When the larvae emerge they feed on the leaves resulting in brown patches. In some of the photos there are smaller brown areas within the leaves whereas other leaves have much larger areas of brown. A healthy tree can usually tolerate the damage from the leafminer so there would be no need for treatment. It is important to keep the trees well watered.

I have included resources on the birch leafminer. If after reviewing the information you do not feel that the findings in your trees are consistent with this pest you could submit additional photos. I am including our plant pathologist as a collaborator on your question.

https://hort.ifas.ufl.edu/trees/BETPAPA.pdf

https://extension.psu.edu/birch-leafminer

https://extension.unh.edu/sites/default/files/migrated_unmanaged_files/Resource002808_Rep4163.pdf

https://extension.umn.edu/yard-and-garden-insects/birch-leafminers

It is interesting that I see the characteristic white bark of Paper birch in only one of the photos. The bark in the other photos looks dark in color and not consistent with Paper birch. I ask because susceptibility to some of the diseases/pests is varied for different species of birch.