Rheumaptera (formerly Hydria) prunivorata

Cherry scallopshell moth caterpillars. Photo: James B. Hanson, USDA Forest Service, Bugwood.
Scientific Name: Rheumaptera (formerly Hydria) prunivorata
Common Name: Cherry Scallop Shell Moth
Growing Degree Days (GDD's): None available at this time.
Host Plant(s) Common Name (Scientific Name)
Black cherry (Prunus serotina)
Cherry (Prunus spp.)
Insect Description:

This inchworm is native to North America. Adult moths emerge throughout the summer (roughly May to August) and have alternating light and dark colored scalloped lines on their wings. Adults have wing spans of approx. 1.45 inches. Emergence peaks in June. Females will lay eggs on the undersides of leaves in masses 1-4 layers thick. Once eggs hatch (from July through early August), larvae or inchworm-like caterpillars will feed in groups on the leaves from July into the early fall while tying leaves together with silk.  Caterpillars feed together on the surface of the leaf, hidden in their nests. Once a leaf is completely stripped, they will move to new leaves and create new nests. Full grown caterpillars are approximately 0.8 inches in length, pale yellow in color with 4 brown dorsal stripes, and an orange-brown head capsule. In the fall, larvae will drop to the leaf-litter and soil surface where they will pupate and overwinter in this stage. (However some larvae have also been observed to pupate within nests created in leaves.) One generation is reported per year.
Damage to Host:

This insect can be an occasional, serious pest of cherry. These looper caterpillars feed inside of nests made of tied together foliage. Heavily infested trees may become completely defoliated. Dieback and decline of cherries may follow an outbreak of this insect.
Monitoring:

Scout for groups of caterpillars tying foliage together, particularly in July and August, on susceptible hosts.
Cultural Management:

Remove groups of caterpillars tying foliage together with silk before defoliation is too extensive. Drop in a bucket of soapy water or otherwise destroy.
Natural Enemies & Biological Control:

As a native insect, the cherry scallop shell moth has naturally occurring parasites, predators, and diseases that typically help keep populations of this insect under control. A species of Telenomus wasp parasitizes the eggs of this moth and has been known to help reduce outbreak populations.
Chemical Management:

Abamectin (NL) 

Acephate (NL)

Acetamiprid (L)

Azadirachtin (NL)

Bacillus thuringiensis subsp. aizawai (L)

Bacillus thuringiensis subsp. kurstaki (NL)

Beauveria bassiana (NL)

Bifenthrin (NL)

Carbaryl (L)

Chlorantraniliprole (NL)

Chlorpyrifos (larvae) (N)

Chromobacterium subtsugae (NL)

Cyantraniliprole (NL)

Cyfluthrin (NL)

Deltamethrin (L)

Emamectin benzoate (L)

Flonicamid+cyclaniliprole (N)

Gamma-cyhalothrin (L)

Horticultural oil (L)

Lambda-cyhalothrin (L)

Methoxyfenozide (NL)

Neem oil (NL)

Pyrethrins (L)

Pyrethrin+sulfur (NL)

Spinetoram+sulfoxaflor (N)

Spinosad (NL)

Tau-fluvalinate (NL)

Zeta-cypermethrin (L)
Notes:

Spraying contact insecticides on caterpillars concealed within their silken webs may not be effective.

Active ingredients that may be applied systemically include: abamectin (injection), acephate (injection), acetamiprid (injection), azadirachtin (injection, soil drench), cyantraniliprole (soil drench, soil injection), emamectin benzoate (injection), and neem oil (soil drench).

When used in nurseries, chlorpyrifos is for quarantine use only.

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: September 27, 2024. To check current product registrations in Massachusetts, please visit the MA Department of Agricultural Resources Pesticide Product Registration page and click on "Search Pesticide Products Registered in Massachusetts - Kelly Solutions".