Red-humped oakworm

The red-humped oakworm (Symmerista albicosta) is a moth species belonging to the family Notodontidae. This insect is primarily recognized as a defoliator of hardwood trees, particularly known for its ability to cause extensive damage to oak forests during peak population outbreaks.

The primary host plants for this species are various oak species (Quercus spp.) and occasionally American beech. When populations reach epidemic levels, they can strip trees of their foliage, creating large, highly visible defoliated areas in the forest canopy that can be observed even from long distances.

The life cycle of Symmerista albicosta is univoltine, meaning there is only one generation per year. The insect overwinters in the pupal stage within the leaf litter or shallow soil. Adult moths emerge in early summer to mate and lay eggs on the undersides of leaves. The larvae emerge and undergo several developmental instars, feeding throughout the summer and into the early autumn.

The larvae are characterized by their gregarious feeding behavior in early stages, moving to solitary feeding as they mature. The damage includes significant leaf tissue consumption, leading to reduced photosynthetic capacity of the trees. Repeated yearly defoliation can cause dieback, branch mortality, and increased vulnerability to secondary pests like wood-boring beetles.

Management and control strategies involve monitoring egg masses and adult flight activity using light or pheromone traps. For direct suppression in high-value stands or nursery environments, the application of biological insecticides, such as formulations of Bacillus thuringiensis, is the preferred approach, as it targets the larvae effectively while preserving natural predator populations.