|Elm Leaf Beetle -
Clemson University, Cooperative Extension Slide Series, www.ipmimages.org
William M. Ciesla, Forest Health Management International,
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.
yellow-green adult beetle overwinters in protected areas, including
buildings. In late spring, beetles emerge and move to elm trees to mate
eggs. Females lay masses of bright yellow eggs that are attached to
surfaces. Larvae hatch after 10-14 days and feed for about 3 weeks.
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.
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).