Coleophora ulmifoliella

Elm casebearer larva case and feeding damage. Photo: Tawny Simisky
Scientific Name: 
Coleophora ulmifoliella
Common Name: 
Elm Casebearer
Growing Degree Days (GDD's): 
300–533, Base 50F, March 1st Start Date. (Source: Cornell Cooperative Extension)
Host Plant(s) Common Name (Scientific Name): 
American elm (Ulmus americana)
Scotch elm (Ulmus glabra)
Slippery elm (Ulmus rubra)
Insect Description: 

This is a native North American moth species. The adult moth is small, with a wingspan of roughly 0.5 inches, with dull coloration (yellowish-beige with gray markings). Mating occurs in late July, after which the female moths lay their eggs on the leaves of elm. Once the eggs hatch, the first instar larva enters the leaf and mines between epidermal layers. Eventually, the larva exits the mine and forms a brown case over itself which will be found on the underside of the leaves. This tube-like case is where the larva spends the rest of its time, serving as protection and enlarging the case as the larva grows in size. In the fall with the advent of cool weather, the elm casebearer larva will migrate to the elm twigs, bringing the case with it, where it overwinters in an immature larval stage. In the spring, once new elm foliage becomes available, the casebearer moves back to the leaves and resumes feeding, while still in the case. The cases rarely exceed 1/4 inch in length. Pupation occurs in time for the adults to emerge again in July. One generation occurs per year.

Damage to Host: 

This pest creates small blotch mines in the foliage. Brown, tube-like cases may be found on leaf undersides. Single casebearer larvae may not cause significant damage, but injury can result from large populations. In heavy infestations, entire leaves are browned and die. 

Monitoring: 

Scout for brown patches between leaf veins in July and August. In the late summer, look for small, brown tube-like cases on the underside of host plant leaves.

Cultural Management: 

Unfortunately, sanitation activities in the fall, such as raking and disposing of fallen leaves, will not typically remove these pests as they move (with their cases) to twigs to overwinter. That being said, this insect poses a low risk for host plant mortality and chemical management is not necessary unless most leaves on the plant contain more than a single larva. It is considered a minor pest in most situations.

Natural Enemies & Biological Control: 

Natural enemies are not reported in detail and require further study. Schaffner (1959) notes the following hymenopteran parasitoids collected from elm casebearers in Vermont and Massachusetts: Apanteles spp., Habrocytus thyridopterigis, and Hypopteromalus spp.

Chemical Management: 

Acephate (NL)

Azadirachtin (NL)

Bacillus thuringiensis subsp. kurstaki (NL)

Bifenthrin (NL)

Carbaryl (L)

Chlorantraniliprole (NL)

Chlorpyrifos (larvae) (N)

Cyfluthrin (NL)

Deltamethrin (L)

Emamectin benzoate (L)

Gamma-cyhalothrin (L)

Indoxacarb (L)

Lambda-cyhalothrin (larva only) (L)

Malathion (L)

Permethrin (L)

Spinetoram+sulfoxaflor (N)

Spinosad (larva only) (NL)

Tau-fluvalinate (NL)

Tebufenozide (NL)

Notes: 

Active ingredients that may be applied systemically include: acephate (injection), azadirachtin (injection, soil drench), chlorantraniliprole (soil drench), and emamectin benzoate (injection).

Make insecticide applications after bloom to protect pollinators. Applications at times of the day and temperatures when pollinators are less likely to be active can also reduce the risk of impacting their populations.

Note: Beginning July 1, 2022 neonicotinoid insecticides are classified as state restricted use for use on tree and shrub insect pests in Massachusetts. For more information, visit the MA Department of Agricultural Resources Pesticide Program.

Read and follow all label instructions for safety and proper use. If this guide contradicts language on the label, follow the most up-to-date instructions on the product label. Always confirm that the site you wish to treat and the pest you wish to manage are on the label before using any pesticide. Read the full disclaimer. Active ingredients labeled "L" indicate some products containing the active ingredient are labeled for landscape uses on trees or shrubs. Active ingredients labeled "N" indicate some products containing the active ingredient are labeled for use in nurseries. Always confirm allowable uses on product labels. This active ingredient list is based on what was registered for use in Massachusetts at the time of publication. This information changes rapidly and may not be up to date. If you are viewing this information from another state, check with your local Extension Service and State Pesticide Program for local uses and regulations. Active ingredient lists were last updated: January 2024. To check current product registrations in Massachusetts, please visit: https://www.mass.gov/pesticide-product-registration .