The Smaller European Elm Bark Beetle

The Smaller European elm bark beetle Scolytus multistriatus, as talked about last week is causing problems in Elm trees. This insect is a wood boring insect; this means that it likes to lay its eggs under the trees bark. This insect also likes to eat at the green sap wood of the tree. This beetle is a brown to auburn in coloring. The adult beetles are approximately 1.9 – 3.1 mm in length. The larva are white in color, these are legless grubs. This bark beetle has one generation in the Canadian climate but is known in other places to have two generations in even warmer climates it can have upwards of three generations per year.

Larva will over winter in the Elm trees until the spring months. Adult exit the trees after the buds break, beetles fly in the summer months, they fly to dying Elm trees. The adults will pick up spores upon leaving the trees. These adults go to new healthy hosts and feed on the soft wood found in tree unions. The beetles that leave the trees between the months of April to the July are the most likely to vector Dutch Elm Disease. At this time of the year the trees xylem is openly flow for the bud break of the tree. The beetles will establish themselves under the bark and interfere with the xylem.

After feeding on the healthy Elms, the adults will tunnel into the dyeing, weakened, dead or in decline Elm trees. The beetles will then lay their eggs, these eggs will hatch and the larva will create feeding galleries. These run parallel with the grain of the wood, these have been said to look like caterpillars with long legs. These larva have a life cycle from 35 to 40 days. The larva become adults and emerges from the trees to feed.