Hi, I'm Jessie Moan with the University of Alaska Fairbanks Cooperative
Extension Service's Integrated Pest Management Program. Today we're going to
go over how to evaluate a dead spruce tree to determine if it has spruce
beetles in it and why it's important to evaluate these trees. This information
can be applied to individual trees in ornamental settings or to small wood
lots or a larger forest setting. This video is part of a series, so be sure to
check out our videos on how to identify the signs and symptoms of spruce beetle
and how to process infested material for more information on those topics.
Trees that have been killed by spruce beetle can support beetle life stages for
roughly 2 years after they have died, so it is important to know what to look
for and what to do with infested dead trees to minimize the spruce beetle risk
to standing live trees in the area. The most important thing to look for is
spruce beetle life stages underneath the bark. The best way to do this is to peel
a section of the bark off and look for beetle life stages. When looking under
the bark for spruce beetle life stages, we are primarily looking for larvae, or
the immature stage; pupae, the live stage that is undergoing transition to
adulthood; and adults. Eggs are very small and less likely to be seen.
It is also important to note that there will likely be a lot of other living things
underneath the bark of the tree. Spruce beetle larvae are small, creamy white, and legless.
Larvae are responsible for the majority of damage caused by spruce beetle.
They may have an orangish-brown head and are overall grub-like in appearance.
Pupae are also creamy white in color but do not completely resemble
either the larvae or adult beetles, though they are similar in overall size
and shape to adults. The pupae are a non-feeding, non-mobile life stage.
Adults are reddish-brown to black in color and about 1/4 of an inch long and
cylindrical in shape. Finding individuals of these life stages means there's a
possibility that beetles could emerge to infest standing live trees in the area.
Infested trees may be prioritized for removal to help reduce beetle
populations and protect surrounding trees. Having a general idea for how long
the tree has been dead is also important so that the proper precautions are taken
when removing trees. A tree that has long since been killed by beetles does not
necessarily need to be removed since once the inner bark of a tree has
substantially dried out, spruce beetles are no longer able to survive in the material.
However, these trees may become a health
or safety hazard as they age. The length of time a tree remains standing after it
dies from beetle attack is highly variable. Environmental factors such as
precipitation and humidity can influence how fast the tree decomposes and,
therefore, how unstable it becomes. If the tree shows obvious signs of rot or is in
danger of crushing infrastructure if it fell, it may be best to remove it as soon as possible.
Cutting or felling trees can be dangerous.
Make sure to take proper safety precautions and wear all personal
protective equipment. If you do not have experience operating a chainsaw, it may
be best to hire a professional instead. Removing infested trees can help manage
future populations of beetles and protect surrounding live trees as long
as the material is processed correctly. Under some circumstances, trees may be
removed to prevent them from becoming a health or safety hazard to people or structures.
The best time to fell an actively infested tree is fall or winter.
This is when beetles are least likely to be active and will still allow plenty of
time to process the felled material. Avoid cutting trees between May and July
during the active beetle flight period as fresh cut material is attractive to beetles.
If necessary, trees can be cut in early spring,
but it is important that the material is processed promptly. After the tree has
been felled, remove the branches. The trunk and any branches greater than 5
inches in diameter should be processed to minimize the possibility of adult
beetles emerging. Stumps should be cut as low to the ground as possible.
The best option is to grind out the stump or debark it to 2
inches below the soil line. Removing infested trees from a property can be
beneficial in reducing spruce beetle populations in the immediate area.
Check your trees for spruce beetle life stages to help determine if the tree should be
removed, and avoid felling spruce trees between May and July. Felled trees should
be processed in such a way that prevents adult beetles from emerging from the cut
tree and prevents attracting new beetles to the freshly cut tree. Knowing what to
do about a dead spruce tree is an important step in making spruce beetle
management decisions. For more information on processing material, see
our video on processing. For more information on spruce beetles and spruce
beetle management, visit www.alaskasprucebeetle.org.