The elm leaf beetle, Pyrrhalta luteola (Muller), is a pest of elm trees in many parts of the United States. It becomes a nuisance when it moves into homes to hibernate for the winter.
The adult beetle is about ¼” long. It is usually yellow or olive colored. There is a dark stripe that runs along the edge of each wing.
The female beetle deposits eggs on the leaves of elm trees. The larvae eat most of the leaf material, leaving only the veins. When the larvae are ready to change to adults, they crawl down to the ground. There are usually two generations in the spring and summer.
In the fall, adult beetles move to the house. They cluster on the house for warmth. Some of the beetles find cracks that allow them to get inside. They hibernate inside the walls and in the attic.
When the weather turns warm, the beetles become active. They try to move outside to the elm trees. Some of them accidentally make their way inside the home. They do not damage anything, but they can be disturbing to the residents.
Elm leaf beetles can be prevented from entering the house by sealing any small openings. Caulk any cracks around doors and windows. Make sure exterior doors close tightly and replace missing weather-stripping. Repair damaged screens on windows and vents – check the attic vents too.
Elm leaf beetles that are damaging trees can be managed with insecticide. To avoid any chance of spray drift, pesticide exposure, or over-spraying, many people prefer to have a pest control professional spray their trees.