Elm Leaf Beetle
- Latin Name: Xanthogaleruca luteola or Pyrrhalta luteola
- Size: ¼” long
- Color: The elm leaf beetle varies between a light yellow and a dark green.
- Shape: Oval with an hourglass mark on its back and a spot on its head. The larvae are usually black and yellow and twice as long.
- Found in: Southwestern states and anywhere elm trees grow.
- Overview: The elm leaf beetle is an outdoor pest found on elm trees.
Origin: These beetles originated in Europe, but have been found from Asia to South America.
Climate: A warm to temperate climate is ideal for the elm leaf beetle. They are unable to survive cold winters outdoors.
Favorite Foods: Unlike other beetles, the elm leaf beetle only eats one thing, elm leaves. They cause the leaves they are feasting on to die, but do not kill the tree. If a tree is infested by a large number of beetles, it may appear dead due to the dried up brown leaves.
Family: The elm leaf beetle is part of the Chysomelidae family. Depending on the temperature outside, two to three generations will hatch during the summer. A female can lay about 800 eggs during her lifetime. The small yellow eggs are found under elm leaves.
Unique Facts: The elm leaf beetle does not lay eggs indoors or feed. They will only eat and lay eggs in elm trees. Larvae will eat the bottom of the leaves and molt three times before crawling to the bottom of the tree to pupate. Each stage of the larvae development is called instars and in total it lasts about three weeks. It takes about eight days once the larva is hidden in the bark near the bottom of the tree to emerge from the pupal stage as an adult beetle.
Signs of a problem: Elm leaf beetles enter homes in the winter to survive. They cannot live outside in the cold. They may enter through cracks, vents or an open window. In the spring, you may find them near a window trying to leave the home. Because they are only inside to hibernate, they typically don’t do damage inside the home. The place where you will notice a problem is on your elm trees. You may see small holes in the leaves or multiple leaves drying up and turning brown in the spring and summer. An elm leaf beetle will not kill your elm tree, but it may weaken the tree making it more susceptible to disease.
Do they attack humans? No, elm leaf beetles do not bite or sting. They are herbivores.
Stopping an infestation: There are two ways to control elm leaf beetles. The first is to allow nature to run its course and stinkbugs or wasps will eat them. They also won’t survive a spring freeze. If natural controls are working slower than you would like, you can spray the elm trees with insecticides. The insecticide can either be sprayed directly onto the leaves and trunk or banded to the tree trunk. Consult a pest control professional on what option is best for your home.