Clemson University, Cooperative Extension Slide Series, www.ipmimages.org

William M. Ciesla, Forest Health Management International, www.ipmimages.org

HOSTS: Elm.

DESCRIPTION: Feeding adults are yellow-green beetles, 1/4 inch long with a dark stripe down the center of their bodies. Overwintering adults are more green in color. Larvae are black with lateral yellow striping, 1/4 inch long, soft-bodied grubs. Pupae are bright yellow.

LIFE CYCLE: The yellow-green adult beetle overwinters in protected areas, including nearby buildings. In late spring, beetles emerge and move to elm trees to mate and lay eggs. Females lay masses of bright yellow eggs that are attached to lower leaf surfaces. Larvae hatch after 10-14 days and feed for about 3 weeks. They then crawl down the tree in search of pupation sites. Most pupate at the base of the tree, or in the folds of bark furrows. Adults emerge in 10-15 days and reproduce to begin a second generation.

CONTROLS:

Cultural: Aerate soil around elm trees, mulch with wood chips or composted bark 2-3 inches deep.

Monitoring: Check for worm-like grubs in late May or early June. Treatment is not required unless trees are 40% defoliated and/or 50% are infested with beetle larvae. It is best to treat when larvae are newly hatched.

Biological: There are many natural enemies of elm leaf beetle, including several parasitic wasps, spiders, ground beetles, lady beetles, and predaceous plant bugs .

Beauveria bassiana and parasitic nematodes (Heterorhabditis spp.) sprayed on the soil surface beneath elm trees reduced elm leaf beetle pupae by 75% in a Minnesota study . In Montana, apply nematodes or Beauveria in june and keep soil moist.

Bt var. tenebrionis is effective on young larvae as long as good foliage cover is obtained. (Bt for caterpillars is NOT effective.) See Bacillus thuringiensis.

Chemical: Neem and oil sprays can control ELB larvae and are reportedly less toxic to lady beetles than soap, carbaryl, or acephate (Kyhl 1998).