A
number of exotic, invasive pests
are causing problems in native and
urban forests across the country. Pests
like the emerald ash borer and gypsy
moth have killed millions of trees
since they were introduced and became
established in the United States. But
not all forest pests are exotic; some of
our native insects can cause serious
damage, too.
The mountain pine beetle
(Dendroctonus ponderosae) is one
example of a native insect pest causing
tremendous damage to trees. The
mountain pine beetle, or MPB, is
native to much of the western United
States, with the eastern range of this
pest butting up to the native pine stands
in western Nebraska. Several species
of pines are attacked by the MPB,
including native ponderosa, limber,
and lodgepole pines and the introduced
Scotch pine.
The MPB is a small beetle, dark
brown or black beetle,
1
⁄8 to
1
⁄3 inch in
length. Adult beetles emerge from pine
trees in mid to late summer. Females
will bore into living trees, creating
galleries under the bark in which they
will lay their eggs. These galleries run
vertical and may be several feet long,
holding up to 100 eggs. Larvae hatch
from the eggs in roughly 14 days and
begin feeding. They tunnel at right
angles to the egg gallery, overwinter
under the bark, pupate and emerge from
the now dead tree the following summer
as adults, ready to infest a new tree.
Signs of beetle infestation include
pitch tubes on the trunk of trees,
which result from resin produced by
the tree pushing out where a beetle
has bored into a tree. Sawdust created
by beetle boring may collect in bark
crevices, and woodpecker damage
may be noticeable. Pine needles turn
yellow to red and ultimately the tree
dies, typically several months after
infestation.
The beetle feeding damage alone
doesn't kill the tree. Blue-stain fungus
is carried on the bodies of MPB,
and as the beetle feeds, it spreads
the fungus throughout the tree. The
fungus disrupts the ability of the tree to
transport water, and the tree dies.
While the beetle is native to the
western United States it is not known
to occur in eastern and southern
pine forests. There is great concern
that should the beetle be introduced,
these forests could be decimated.
Firewood is one way that this
pest could easily be transported to
uninfested areas. Remember not to
travel with firewood; obtain it when
you get to your destination, and leave
any unburned firewood behind. Visit
dontmovefirewood.org for more
information on pests that move in
firewood. ■
MARCH 2017 • NEBRASKAland 17
Bug Banter
By Julie Van Meter
State Entomologist, Nebraska
Department of Agriculture
Mountain Pine
Beetle
Presented by
