Health Protection, Southern Region
ELM LEAF BEETLE,
Pyrrhalta luteola (Mueller)
Importance. -- The elm leaf beetle attacks all species of elm. However, in most of its range, the beetle prefers the Siberian elm. When defoliation is severe for
several consecutive years, limbs and sometimes the tree may be killed. The beetles may become a nuisance in the fall when they move into homes searching for
overwintering sites. The adults may be a problem in the spring when they congregate in windows as temperatures increase.
Identifying the Insect. -- The larvae are green to yellow, with a black head and two black stripes on the back. Pupae are about |/4 inch (6 mm) long and bright orange-yellow.
The adults are approximately l/4 inch (6 mm) long and yellowish to green with a black stripe on each wing margin.
Typical damage and life stages - adults,
larvae, and eggs. (Click for detail. JPG 17K).
Identifying the Injury. -- Adults chew holes in the leaves, particularly on new growth. The larvae feed on the under surfaces of leaves, leaving upper surfaces and the
veins intact. Leaves shrivel and turn brown when damage is severe.
Biology. -- In the spring the adults fly to elms and eat small holes in the newly developing leaves. Eggs are laid in a cluster on the undersides of leaves. The eggs hatch
and the larvae feed for 2 to 4 weeks. The larvae crawl to sheltered places on the tree or ground to pupate. In one to two weeks new adults emerge and again feed and
lay eggs. There are two to four generations per year, depending on the geographical location.
Control. -- No chemical controls are recommended in forest stands. Homeowners may use recommended insecticides to protect valuable
shade trees. Sprays should be directed at the undersides of the leaves, beginning in the early spring.