American Dagger Moth

From Bugwoodwiki

Hexapoda (including Insecta)
A. americana
Scientific Name
Acronicta americana
Common Names
American dagger moth

Compiled by Whitney Cranshaw, Colorado State University:

Acronicta americana (Harris)
Lepidoptera: Noctuidae


Primarily silver maple but occasionally other maples including boxelder

Damage and Diagnosis

Larvae feed on foliage and have the unique habit of clipping off partially eaten leaves in order to avoid detection by predatory birds. Leaves on the lawn with portions of the petioles attached are characteristic and indicate dagger moth feeding overhead. The larvae somewhat resemble yellow-haired "woolly bears" and may be found wandering in the vicinity of infested trees.

Life History and Habits

The adult stage is a moderately large (wingspan of about two inches) brown moth named after a dagger-like marking on the forewing. After emerging from the overwintering pupa, adult moths are present through much of spring and lay eggs on the newly emerged foliage of maple. The eggs hatch in late spring and larvae feed throughout the summer. In early fall they crawl down the tree trunk in search of pupation sites and may be encountered dozens of yards from the host tree at this time. Finding a suitable sheltered spot they spin a dense silken cocoon and pupate within it. There is one generation per year.

Related Species

Other dagger moths can be found in the region, including the poplar dagger moth (A. leporina L.), that feeds on poplar, willow and birch. Habits and general appearance of the caterpillars are generally similar.

The information herein is supplied with the understanding that no discrimination is intended and that listing of commercial products, necessary to this guide, implies no endorsement by the authors or the Extension Services of Nebraska, Colorado, Wyoming or Montana. Criticism of products or equipment not listed is neither implied nor intended. Due to constantly changing labels, laws and regulations, the Extension Services can assume no liability for the suggested use of chemicals contained herein. Pesticides must be applied legally complying with all label directions and precautions on the pesticide container and any supplemental labeling and rules of state and federal pesticide regulatory agencies. State rules and regulations and special pesticide use allowances may vary from state to state: contact your State Department of Agriculture for the rules, regulations and allowances applicable in your state and locality.