Participants at last week's Greater Cincinnati Diagnostic Walk-About were thrilled to view the unusual leaf symptoms caused by the Redbud Leaffolder (Fascista cercerisella; order Lepidoptera; family Gelechiidae) on its namesake host. Or, maybe it was just me who was thrilled.
While populations are not as high as in 2016, it is not uncommon to find redbuds with leaves turning brown after being folded over or "glued" together. I'm not aware of any host preference studies for this native moth; however, the damage has always seemed more evident on weeping redbuds. Of course, this could simply be due to the damage being more obvious because of the vertical orientation of the leaves.
Three overlapping generations of this velvety black moth occur per season in Ohio with 2nd and 3rd generation nests usually containing caterpillars in various stages of development. Populations tend to build with each generation meaning that the most significant damage occurs late in the season. The moth spends the winter as pupae in debris and fallen leaves beneath infested trees.
The leaffolder caterpillars produce nests described by their common name by using silk stitching to fold over leaf edges. However, the nonconformist caterpillars also make nests like those produced by a "leaftier" by stitching together neighboring leaves. In fact, in my opinion, the high frequency of tied-together leaves challenges the correctness of the caterpillar's common name.
The caterpillars reside in heavy silk tubes within both types of nests. They partially emerge out of their tubes to feed as skeletonizers, consuming the upper and lower leaf surfaces. The affected areas turn orangish-brown which sharply contrasts with the normal dark green color of the foliage.
Early instar caterpillars are cream-colored and have no discernible markings. As the caterpillars mature, markings begin to develop with alternating segments darkening to produce a striking appearance of black and light-green bands running the length of the body. They resemble tiny banded sea kraits (snakes). When disturbed, the caterpillars wiggle back and forth violently further enhancing their tiny snake impersonation. They have great entertainment value!
Insecticidal applications are not generally required for managing this moth in Ohio landscapes. Besides, the caterpillars live in protected locations which makes the successful use of insecticides problematic.
Most of the leaf damage is produced by the current 3rd generation caterpillars. Trees have already generated and stored enough carbohydrate to support the production of new leaves next season. Consequently, the leaffolder has a limited impact on the overall health of the tree even during localized population outbreaks.
Where practical, populations can be reduced by pinching nests to kill caterpillars. Raking and destroying fallen leaves will also reduce localized numbers by eliminating overwintering moth pupae.