By Debra A. Parker
Those leaffolding caterpillars are at it again.
This spring I think every tree in Oklahoma had the problem. But additional generations of the pesky caterpillars are back for a second act this fall.
I can appreciate insects that have been adapting for millennia; creating a folded leaf to hide and feed at the same time is pretty brilliant in my opinion. Some of you may not be as smitten, so let’s talk about some options for control if you have folded leaves on your redbuds.
Like the name, the noticeable injury to a redbud leaf is the folding down of the edge of the leaf onto the upper surface of the leaf. The edge of the leaf is then secured with strands of silk.
In heavy infestations, there may be several areas of the leaf margin folded over. The purpose of the leaffolding is to enable the caterpillar to feed on the upper surface of the leaf, and also serves as shelter for the developing insect. Feeding can lead to browning, dying, and death of the leaves.
The redbud leaffolder winters as a dark brown pupa attached with a loose web to a fallen leaf. Without the leaf, they still may thrive in leaf litter or on the soil surface. Adult leaffolder moths are around a quarter-inch long with a half-inch wingspan. The moth has dark brown wings with 10 small white spots, a white head and collar.
Moths of the leaffolder emerge late spring, laying small, white, oval eggs near leaf veins during the month of May. The first generation of eggs will continue hatching through June, followed by second and third generation eggs laid in late summer to fall. Second and third generation eggs may be laid in a fine web on the leaf.
The damaging stage of the leaffolder is the larvae or caterpillar stage. The young larvae are white, but mature to about half-inch long dark caterpillars with white bands along the back.
Since pupa overwinter on fallen leaves, raking and disposing of dropped leaves this time of year is a sufficient means of control. If you begin noticing damage again next spring, the organic insecticide Bacillus thuringiensis (Bt) is effective against the larval stages of many types of leaf feeding larvae, including leaffolders. Bt is a bacterial based insecticide that kills moth and butterfly caterpillars, but does not harm other beneficial insects, birds, humans, or other organisms.
With Bt, leaffolders will cease feeding within hours after ingesting a sprayed leaf and die several days later. Thorough spray coverage of the tree is required for control and Bt is not waterproof.
Caterpillars must feed on leaves dusted or sprayed with the pesticide to be killed. Bt is most effective on leaffolder larvae when small and sufficient control may require more than one application.
Tracey Payton Miller is a horticulture extension educator with Oklahoma Cooperative Extension Service. She can be reached at 405-321-4774.