Perennial vines in the genus Vinca have proved to be sturdy and seemingly indestructible groundcovers for the Southeastern Unites States. However, over the past few years, vinca leaf-folder caterpillars have been ravaging landscape plantings of perennial vincas (Vinca major and Vinca minor). Both can be infested, but V. major seems to sustain more damage. According to Dr. Matt Bertone, Entomologist at NC State University, this pest is likely Diaphania costata.
The larvae wrap themselves in leaves and spin connections between the two edges, effectively folding them and creating a little protected hideaway where they can feed. The caterpillar feeds in its leafy home until it must move to a new one. Eventually, it pupates, becoming a small white moth.
This insect has been common in Texas for about 40 years but has spread eastward from there. Detections in the southeast started in 2009 (Hayden et al.). The worst damage starts showing up in July and August when vinca plantings can take on a scorched appearance.
When damage is severe, infested stems should be cut out and destroyed; large plantings can be sheared or mowed with a bagger attachment from which clippings are disposed. Otherwise, rake out sheared stems and destroy. New stems and leaves will form, which will produce new leaves that may escape a new infestation. However, there are several generations each year, so the infestation can continue into October. The following year, follow a preventive approach by applying an insecticide when damage is first noticed. Since these are caterpillars, the bio-control insecticide, Bacillus thuringiensis (e.g., Thuricide) could be used. Spinosad (e.g., Monterey Garden Insect Spray) is another environmentally safe and effective choice. Both of these are most effective if applied when the caterpillars are young.
For more information on problems with perennial vinca, see HGIC 2108, Vinca Diseases.
- Hayden, James E., Richard Hoebeke, Matt Bertone, and Vernon A. Brou, Jr., Diaphania costata (F.) (Lepidoptera: Crambidae: Spilomelinae), A Commonly Misidentified Pest of Ornamental Apocynaceae in the Southern United States, Proc. Entomol. Soc. Wash. 119 (2) 2017, pp173-190.