The Helena's Trees of Many Colors:

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The Helena's Trees of Many Colors Why Some
Evergreens Are No Longer Green!
The Helena National Forest is undergoing
landscape-level changes in the forest due to
insect activity, as evidenced by the red trees
visible to anyone living in or visiting our area.
The primary culprit of the mortality is the
mountain pine beetle, with help from other
insects such as the western spruce budworm and
the Douglas-fir beetle. All of these insects are
native to our ecosystem and have evolved with the
tree species on the Helena National Forest. These
large-scale ecological disturbances are beyond
our capability to control however, management
opportunities do exist that can be effective in
localized areas.

How Did We Get Here?
Several factors have combined over the years to
create the homogenous, same aged, susceptible
forests we have today. These combining factors
include The small extent of harvest in recent
decades. The
recent warm and dry climate.
Fire
suppression.

Harvest practices around the turn of the century
that have created even-aged forests.
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First and Foremost, The Mountain Pine Beetle
Most of the red trees we are seeing on our forest
have been killed by mountain pine beetle, which
is an aggressive bark beetle affecting pine trees
(ponderosa pine, lodgepole pine, whitebark and
limber pine). It is estimated 350,000 acres or
36 of the Helena National Forest is infested by
mountain pine beetle.
When a beetle emerges from under the bark of a
tree in late July it will generally fly to the
nearest susceptible tree, which is usually the
largest living trees available. The beetles will
also fly to weakened trees as small as 5
diameter. Infestation is often indicated by pitch
tubes on the bark mid to late summer and large
amounts of saw dust in bark crevices and around
the base of the tree. Infested trees generally
stay green for up to 1 year.
The mountain pine beetle is tiny, about the size
of a cooked grain of rice. When a beetle
successfully attacks a pine tree it will lay its
eggs in the cambium layer, just underneath the
bark. The cambium layer is the vascular system of
the tree that moves water and nutrients from the
roots to the canopy. Hatching larvae require a
softened (damaged) cambium layer for food. This
is essentially what kills the trees.
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What Can Be Done to Help???
The first step in a good strategy is to develop
realistic goals and outcomes. It is important to
accept that we cannot stop a beetle epidemic in
progress, particularly one that crosses national
borders in extent. Even with limitless funds and
labor, it would not be possible to remove every
infested tree, to spray every susceptible tree,
or to thin every forest. We can, however, impact
small localized areas and specific trees or
groups of trees by applying these mountain pine
beetle management options.
SANITATION Removal of currently infested trees
can reduce the localized beetle population. Trees
that are currently infested are generally those
that have numerous pitch tubes but still appear
green. Looking for beetles or larvae under the
bark is the best way to identify infested trees.
THINNING Creating a resilient stand is the best
long-term way to reduce susceptibility and
mortality a spacing of 20-40 feet between trees
is best. Depending on how big the trees are --
the bigger the trees, the wider the spacing needs
to be.
VERBENONE Verbenone is a chemical,
acting as a pheromone inside of a plastic
capsule. These capsules are stapled onto trees
either on a grid basis for large areas or on
individual trees (2-4 per tree). Verbenone is
50-90 effective. These capsules are generally
8-9 per packet and should be put up late May to
early June. To purchase Verbenone contact the
Montana Discovery Foundation at (406)-495-3711.
SPRAYING CARBARYL This chemical can be used to
protect individual trees from infestation. The
ENTIRE trunk must be soaked with the appropriate
mix of chemical (42 concentrate) to 50 feet high
or where the tree is 5 inches diameter. This
method when done can be 100 effective and may
last for 2 seasons.
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Next, The Western Spruce Budworm
Western spruce budworm is a native defoliator of
Douglas-fir, spruce, and true firs. It does not
affect pine species. It eats the new needles of
affected trees in the early summer as a
caterpillar, causing the branch tips to look
curled and brown. The insect becomes a moth in
mid to late summer and lays its eggs which spend
the winter inside branch tips and buds.
This insect does not typically kill mature trees
although it can kill saplings and seedlings. It
also causes stress and deformation, which may
result in the tree attracting other mortality
agents such as the Douglas-fir beetle. The
western spruce budworm has chronic epidemics on
the Helena National Forest about every 20 years.
Although western spruce budworm does not
typically kill mature trees, it has caused
atypical mortality in the Flesher Pass area.
Managing stands to be more open is a good way to
prevent severe defoliation of the trees. It is
also possible to spray an insecticide (Bacillus
Thurengiensis) over the crowns of trees in the
spring to prevent defoliation.
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Last, But Not Least, The Douglas-fir Beetle
Douglas-fir beetle is a native bark beetle which
attacks large Douglas-fir trees, over 14
diameter. This beetle is moderately aggressive
and can kill healthy trees when populations are
elevated. Populations may become elevated after
fires or during periods when trees are stressed.
The Douglas-fir beetle became elevated after the
large fires of 2000 in the Big Belt Mountains,
but has since decreased and is currently
affecting little of the National Forest.
However, the insect is still present and large
trees experiencing budworm defoliation or other
stressors could provide hosts to build its
population. Infestation is evidenced by
reddish-brown boring dust on the bark, even
though the foliage may appear green for a year
after the attack. Keeping a stand density low and
removing already infested trees, can reduce the
likelihood of Douglas-fir beetle attacks. The
pheromone capsules of MCH can protect healthy
trees from future attacks.
For more information please feel free to contact
the BUG
LINE at (406)-495-3755!