Elm Leaf Beetles
Facts, Identification & Control
Pyrrhalta luteola (Muller)
Adult elm leaf beetles are about 13 mm long. They are yellow to olive colored. They have a dark band on the outside edge of each wing cover. The larvae are yellow and have a black stripe.
Behavior, Diet & Habits
The elm leaf beetle, Pyrrhalta luteola (Muller), is an important pest of elm trees in many parts of the United States. It can be a nuisance in homes in the fall when adult beetles start looking for a place to spend the winter.
The female beetle lays eggs on the leaves of elm trees. The larvae and the adult beetles eat the leaves. The larvae crawl down the tree and hide when it is time to change to adult beetles. In some areas of the country, there are two or three generations during the summer.
In the fall, the adult beetles try to find a place to spend the winter. Many times they gather on houses and then find openings that lead to the inside. They spend the winter in attics, crawl spaces, or hiding in the living space. When spring comes, they become active. They try to move outside to go to the elm trees and lay eggs. When they are trapped inside the home, they gather at windows and doors and become a nuisance to the people who live in the home.
Mating occurs in the spring once the beetles emerge from their overwintering hiding places. Females can produce up to 800 eggs in her life. She usually places them underneath the leaves of the plant. Larvae hatch, feed and then pupate in crevices in the tree toward the end of the summer. Adults will seek overwintering crevices.
Signs of an Elm Leaf Beetle Infestation
In homes the mass migration of the adult beetles is the most obvious sign. In the outdoors, elm trees that show browning leaves and premature leaf drop can indicate elm beetle activity. A closer inspection of the plant would be needed to detect the feeding larvae.
There are a variety of products that will control elm leaf beetles while they are on the trees. There are biological agents, insecticidal soaps and oils, and systemic products. The specialists at the garden center can help with these. Follow label directions for these products. Controlling the beetles on the trees will reduce the number of beetles that try to enter the home. It will also reduce the amount of damage that the beetles might do to the trees.
To keep elm leaf beetles from entering the home, check the outside for openings. Repair screens on windows, attic vents and crawl space vents. Make sure exterior doors close properly. Add weather-stripping where it is damaged or missing.
An insecticide barrier on the outside of the house will reduce the number of adult beetles that gather there. It will help prevent beetles from entering the home. The choice of product and formulation is important to ensure effectiveness. Your local pest control professional will have the products and the equipment necessary to treat the home to prevent outdoor pests from invading.
Beetles that get inside will not cause any structural damage to the home. They do not bite or sting. The quickest way to remove these beetles from the inside of the home is with a vacuum cleaner.