Cottonwood dagger moth

The cottonwood dagger moth (Acronicta lepusculina) is a moth species belonging to the family Noctuidae. It is widely recognized as a defoliating pest that affects various broadleaf trees, and its common name reflects its strong association with cottonwood and poplar species.

These moths primarily feed on the foliage of trees within the Salicaceae family. While cottonwoods are the primary target, they also feed on aspen, white birch, and willow. The insect is widely distributed across North America, often causing noticeable defoliation in both natural stands and urban environments.

The life cycle begins with eggs laid on the leaves, followed by the larval stage, which is the most destructive phase. The larvae are distinct, often covered in dense tufts of hair. As they progress through their instars, their appetite increases, leading to more extensive feeding damage to the host plant.

Feeding damage is characterized by ragged holes in the leaves, progressing to skeletonization where only the veins remain. Severe infestations can cause significant stress to the tree, reducing its ability to store energy for the following season and potentially causing crown dieback in weakened individuals.

Management of the cottonwood dagger moth focuses on early detection and intervention. Horticultural oils and microbial insecticides (such as Bt) are often effective when applied during the early larval stages. Maintaining tree health through proper watering and fertilization also helps trees withstand limited feeding damage from these insects.