The unusual damage caused by the Redbud Leaffolder (Fascista cercerisella, family Gelechiidae) on its namesake host (Cercis canadensis) is becoming evident as caterpillars develop through the final generation this season. Populations are sporadic and highly localized with the most dramatic damage appearing on weeping redbuds.
The native caterpillars use silk stitching to produce two types of nests. Leaf edges may be folded over to produce nests that conform to the "leaffolder" common name. However, the nonconformist caterpillars also make nests like those produced by a "leaftier" by stitching together neighboring leaves. In fact, various online resources may refer to the caterpillars as the redbud leaftier.
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!
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.
I'm not aware of any host preference studies for this native moth. However, I've observed that the damage has always appeared more severe on weeping redbuds. Whether this is due to host preference or simply because the vertical orientation of the leaves makes the damage more obvious is an open question.
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.