Xanthogaleruca (formerly Pyrrhalta) luteola

Elm leaf beetle adult. Photo: Joseph Berger, Bugwood.
Scientific Name: Xanthogaleruca (formerly Pyrrhalta) luteola
Common Name: Elm Leaf Beetle
Growing Degree Days (GDD's): 363–530 GDD's, Base 50F, March 1st Start Date. (Source: Cornell Cooperative Extension)
Host Plant(s) Common Name (Scientific Name)
American Elm (Ulmus americana) *Not preferred.
Chinese Elm (Ulmus parvifolia) *Not preferred.
Elm (Ulmus spp.)
English Elm (Ulmus procera) *Preferred host.
Japanese Zelkova (Zelkova serrata)
Siberian Elm (Ulmus pumila) *Preferred host.
Insect Description:

This species was accidentally introduced into the eastern United States early in the 1800's. Since then, it has been found throughout the USA anywhere elms are located. It also occurs in eastern Canada. The adult elm leaf beetle overwinters in protected areas, such as the loose bark of trees, but can also be a nuisance when it tries to invade homes in search of overwintering protection. Beetles will try to enter houses or sheds in the fall. In the spring, the adult beetles will fly back to the host plant and chew small, semi-circular holes in the leaves. The adult female can lay 600-800 yellow eggs in her life. Eggs are laid in clusters on the leaves and resemble pointy footballs. Larvae are tiny, black, and grub-like when they hatch from the egg. Young larvae will skeletonize the undersides of leaves. As they grow in size, the larvae become yellow-green with rows of black projections. Oldest larvae may appear to have two black stripes along their sides, made from the black projections. There are 3 larval instars. Mature larvae will wander down the the trunk of the host tree and pupate in the open on the ground at the tree base or in cracks and crevices in the trunk or larger limbs. They spend approximately 10 or so days as a pupa, and then the adults emerge. Those adults will fly to the foliage of the same host plant or other adjacent potential hosts in the area, where they will lay eggs. In the fall, the adults will leave the host plant in search of overwintering shelter. In most locations in the USA, two generations of this insect are possible per year. In warmer locations, 3-4 generations per year are possible.
Damage to Host:

Leaves are skeletonized by the larvae. Skeletonization may cause the leaf to turn brown or whitish. Adults are capable of chewing through the leaf, often in a shothole pattern. When in very large populations, they are capable of completely defoliating plants. Populations of this insect can fluctuate from year to year, and often management is not necessary if populations are low. However, defoliation for consecutive seasons may lead to branch dieback or death of the entire tree.
Monitoring:

Visual inspection of leaves at weekly intervals in the spring to look for clusters of yellowish-gray eggs and larvae. Scouting in August and September should focus on the base of trees, looking for pupating insects.
Cultural Management:

Healthy trees can tolerate damage to their leaves. Maintain tree health and vigor.
Natural Enemies & Biological Control:

Predators include certain bugs, earwigs, lacewing larvae, and predaceous ground beetles. Oomyzus (Tetrastichus) brevistigma is a parasite of elm leaf beetle pupae and Oomyzus (Tetrastichus) gallerucae is a parasite of elm leaf beetle eggs. Both are tiny wasps. In California, a small, black tachinid fly (Erynniopsis antennata) is a larval parasite of the elm leaf beetle.
Chemical Management:

Abamectin (NL)

Acephate (larvae) (NL)

Azadirachtin (NL)

Beauveria bassiana (NL)

Bifenthrin (NL)

Carbaryl (L)

Chlorpyrifos (N)

Chromobacterium subtsugae (larvae) (NL)

Clothianidin (NL)

Cyantraniliprole (NL)

Cyfluthrin (NL)

Cypermethrin (NL)

Deltamethrin (L)

Dinotefuran (NL)

Flonicamid+cyclaniliprole (N)

Gamma-cyhalothrin (L)

Horticultural oil (larvae) (L)

Imidacloprid (L)

Insecticidal soap (NL)

Lambda-cyhalothrin (L)

Permethrin (L)

Pyrethrins+sulfur (NL)

Spinetoram+sulfoxaflor (N)

Spinosad (NL)

Tau-fluvalinate (NL)
Notes:

Active ingredients that may be applied systemically include: abamectin (injection), acephate (injection), azadirachtin (injection, soil drench), clothianidin (soil drench), cyantraniliprole (soil drench, soil injection), dinotefuran (soil drench), and imidacloprid (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".