This mid-summer tree issues update comes from the Wisconsin DNR and highlights multiple issues and insects that may also occur across the landscape in Michigan.

One issue is heavy seed crops from maple trees this year. When trees produce so many seeds, it reduces the amount of energy available for producing leaves. As a result, leaves can appear smaller and off-color into the summer. With fewer leaves produced, these trees will continue to look very thin throughout this year’s growing season.

The maple petiole borer is an exotic sawfly insect whose larvae bore into maple the leaf stems or petioles, primarily sugar maple, damaging the petiole tissues and causing the leaves to drop prematurely.

The ocellate gall midge larvae feed on the leaves of maple trees causing the leaf to develop telltale colorful, concentric circles in that area of the leaf. Problems that might look similar include fungal leaf diseases and are cosmetic issues that do not impact the health of the tree.

The woolly elm aphid causes leaves to curl at the edges and develop a characteristic wrinkled appearance. Chemical control is generally not necessary and is rarely effective, because the aphids are protected within the curled leaf of the elms.

The dusky birch sawfly feeds on white birch and occasionally river birch and yellow birch. The defoliation is typically light, with a few dozen leaves per tree being eaten. This defoliation is only problematic on young seedlings with few leaves.