Common name: Elm Leaf Beetle
Scientific name: Order Coleoptera, family Chrysomelidae, Pyrrhalta luteola
Sizes: Adult--1/4", larva--1/2"
Identification: The adult is a yellow to dull green beetle with black stripes on each side. Small yellow to black larvae.
Biology and life cycle: Two to four generations a year. Adults feed on emerging foliage and lay eggs soon after. Females lay double rows of yellow eggs on the underside of elm leaves--usually 25 in each spot for a total of 400. Larvae hatch out in about a week and feed on leaves. Overwinter in the adult stage. Complete metamorphosis.
Habitat: Siberian elm, which is commonly misidentified as Chinese elm, is the favorite plant of this insect, although it will eat other elms as well, especially if they are in poor health. American elms are common hosts, and damage will sometimes be present on lacebark elms and cedar elms.
Feeding habits: Larvae eat green tissue from the surface of leaves. Adults eat holes in elm tree leaves and cause a skeletonized look.
Economic importance: Disfigure elm trees; will sometimes come into the house and be a nuisance. Extremely destructive to ill-adapted elm trees.
Natural control: Birds. Don't plant Siberian elms and cut down the ones you have.
Organic control: Bacillus thuringiensis 'San Diego'.
Insight: Elm leaf beetles are not native. They were brought here from Europe in the early 1800s and have naturalized throughout the country. Yellow beetles with black stripes that skeletonize leaves of elms and others. Spray citrus oil or horticulture oil for severe problems. Garrett Juice with garlic-pepper tea works. Neem oil is another good tool.
Plant better quality trees. Spray if necessary with Bacillus thuringiensis ‘San Diego’. Spray per label at dusk. Add 1 tablespoon molasses per gallon of spray.