Elm Bark Beetle
Scolytus schevyrewi (Semenov)
bark beetle affecting elm trees, identified in Cheyenne in 2003,
has since been found throughout Cheyenne and areas surrounding
Cheyenne. Due to the number of locations that it has been found,
the beetle had probably been in Cheyenne for several years prior
to 2003. The banded elm bark beetles were found feeding in the
cambium layer under the bark on Siberian elm (Ulmus pumila), commonly,
but incorrectly known as Chinese elm. The banded elm bark beetle
is thought to primarily attack trees under stress. Stress, for
example, caused by drought, herbicide damage, hail damage, root
damage, or other insect or disease attack.
Banded elm bark beetles and larva on a dime.
Banded elm bark beetle showing dark band over the back wing coverings.
Cheyenne Forestry Division
The banded elm bark beetle, (Scolytus schevyrewi), originally
comes from parts of Russia, Mongolia, China and Korea. It is suspected
that the banded elm bark beetle was introduced into the United
States in wood packing material such as wooden crates, and pallets.
article from China states that the banded elm bark beetle overwinters
in the tree in mature larva form. The larva will pupate when temperatures
exceed 15°C (60°F). Under field conditions it took 41-45
days to complete a generation. A generation consists of these
stages: egg, larva, pupa, adult. The larva stage is the most destructive
since it feeds on the cambium layer (growth cells under the bark)
and phloem cells (food conduction tissue under the bark). The
adult banded elm bark beetle emerges from a tree after pupation
and can fly to a different tree or unaffected parts of the same
tree. The extent of beetle flight and the infestation range can
be dependent on prevailing winds. In the banded elm bark beetle's
native range there are two to three generations per year. At two
discovery sites on September 29, 2003, in Cheyenne, all life stages
were present, eggs, larvae, pupae, and adults.
Two separate Siberian elm trunks showing
the oozing of sap from Banded Elm Bark Beetle entry holes. Sometimes
the sap flow pushes out the attacking beetle. If the beetle successfully
enters the cambium layer of the tree trunk or limb, eggs are laid.
The eggs hatch and the larvae begin to feed in the cambium and
phloem layers under the bark. One adult beetle entry hole can
equal 20 - 50 exit holes.
Photos: Cheyenne Forestry Division
holes in a Siberian elm trunk made by the adult banded elm bark
you see this, the insect is gone and the damage is done.
Wyoming State Forestry Division
Presently, it is not known if the banded elm bark beetle carries
Dutch elm disease fungal spores. The European elm bark beetle
is a common bark beetle in the area and a known carrier of Dutch
elm disease fungal spores. The Scolytus schevyrewi seems
to be closely related in formation to the European elm bark beetle
affected by the Banded elm bark beetle in the native range are
various species of elm, willow, Caragana (peashrubs), Russian-olive,
and some fruit trees in the Prunus genus like plums, and cherries.
In Cheyenne, Siberian elms are the only trees known to be attacked,
of the Banded elm bark beetle includes: Removing infested wood
and burning it immediately, chipping it into small chips, or burying
it in a landfill. Chipping the wood will allow the living tree
cells to quickly dry out. Adult beetles present in the wood could
survive the chipping process and fly away to infect other nearby
trees. Chipping is probably not the best solution, although it
is better than doing nothing. In no case should the infested
wood be stored as firewood or transported out of the area as firewood. Chemical control for borers in
general includes: Surface spraying the trunk to the point of runoff,
in mid April, with Astro, a Pyrethroid insecticide or an insecticide
Don't Move Firewood
possible, take a couple of digital photos of your tree or shrub
and include them with your questions. One photo should be a close
up of the problem area. The second photo should be of the entire
tree if possible.