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Drought
On average, Estes Park receives about 14.5
inches of precipitation a year. Drought cycles are regular
occurences, and we’re in a period of drought now that began
in 2000. Combined with higher than normal temperatures, this
drought has resulted in stress for all trees. Many trees
have died as a result.
Contributing to the effects of drought are
things like dwarf mistletoe, a parasite that takes moisture
and food away from a tree. Trees weakened by drought and
mistletoe are open to insect infestations, such as mountain
pine beetles and ips beetles.
Under continued drought conditions, trees can
be helped with frequent watering throughout the year. For
effective watering, it’s important to understand the tree’s
root system. The roots that conduct moisture to the tree are
located in an area from the drip line outward one-and-a-half
times the distance from the trunk to the drip line.
The drip line encircles the tree under the
tips of its longest limbs. If the distance from the trunk to
the drip line is ten feet, watering should be done from the
drip line fifteen feet outward. Watering the trunk of a tree
does little, if any, good and may actually harm it.
On smaller trees, encircling the watering
area with a mound of soil will create a dam, retaining the
water in the area where it needs to be absorbed.
Hand-watering this area once a month when precipitation is
below normal will help. Unless there has been sufficient
snowfall followed by melting conditions, watering should
also be done in winter.
It’s especially important to water young
trees. An installed drip system gives the best results.
For more in-depth information on watering and
an illustration of a tree’s root system, visit this website
on
watering plants.
Trees that are stressed by lack of water are
particularly susceptible to insect infestation, which we
will discuss next.
Insect
Infestations
You need only travel to Grand Lake and the
Shadow Mountain Reservoir area to see the results of
epidemic insect infestation. Virtually every pine tree in
thousands of acres of forest has been killed by pine beetles
in an unprecedented epidemic. Nearby Summit County may lose
as much as 90 percent of its coniferous forests, according
to reports.
In the
Estes Valley, nearly 200 inspections were preformed by
trained volunteers in 2008 which showed 502 beetle infested
trees in the area. A map of the compiled results is
available here.
In Colorado as a whole, pine beetles have
destroyed as estimated 7.4 million trees on 1.5 million
acres of the 14.5 million acres of national forest land in
the last ten years, according to a news story in The Denver
Post.
Causes of this destruction are attributed to
a century of fire suppression that has created unnaturally
thick forests, a decade of drought that has weakened the
defense system of trees, and warmer than average winters.
Temperatures of minus 30 degrees are needed to kill beetles
within the trunks of trees.
Fortunately, the Estes Valley and most of the
Front Range has escaped the devastation seen on the western
slope. But only an educated public can help prevent an
epidemic outbreak and control it should it happen here. This
part of our website intends to help our community do just
that.
In this section, we’ll discuss mountain pine
beetles, Douglas-fir beetles, Ips beetles,
spruce
bark beetles, red spider mites, and dwarf mistletoe.
Mountain Pine
Beetles
Mountain pine beetles, also known as bark
beetles, are perhaps the greatest threat, outside of
wildfire, to the pine trees of the Estes Valley—ponderosa,
lodgepole, and limber pines. And they can be just as
devastating as a fire, as a trip to the Grand Lake area
proves.
Many other areas of Colorado have also been
devasted by attacks from pine beetles. Entire mountainsides
have turned from green (live pines) to a washed-out red
(dead pines). Attacks often went unnoticed for years, until
blankets of red appeared. The Estes Valley has been spared
such destruction simply because residents here have
recognized the effects of pine beetle infestations and have
responded with proper treatments.
A map of the
current status of mountain pine beetles in
Colorado is available from the Colorado State Forest
Service. You’ll see that areas around Estes Park are
infected, and you’ll see how the beetles have devastated
areas to the west.
Pine beetle attacks cannot be entirely
eliminated, but if residents remain watchful and take care
of each problem as it appears, our valley can continue to be
blanketed with our beautiful evergreen trees.
Many factors that contributed to the epidemic
on the West Slope—drought, warmer than normal winter
temperatures, and fire suppression—are also in play on this
side of the mountain. Others are not. These include the lack
of species diversity and high-density forests.
Most foresters think that an epidemic of the
proportions seen on the West Slope is not as likely here.
However, what has happened there is on a scale never before
seen in Colorado. Those same foresters urge diligence in
controlling beetle outbreaks before they get out of hand.
According
to the
Larimer County
Forestry
website, the number of trees infested with mountain pine
beetle is increasing statewide. In 2004, 1,256,320 trees
were affected, compared with 275,000 in 2000 and only 13,000
in 1996. Estes Park is listed as an area of concern in the
county due to increased attacks.
This part of the Save Our Trees pages will
give you information on recognizing beetle attacks, treating
beetle-kill trees to prevent further spread of the insects,
how to get free inspections of your trees, and preventing
beetle-kill on your property. Links to additional
information on pine beetles are included.
Recognizing Beetle Attacks
Mountain pine beetle attacks on mature pine
trees come in summer and early fall, from early July
until the first of October. (Global climate changes may
extend these dates.) You can recognize attacks by the pitch
tubes on the tree’s trunk. The tubes are white or reddish
masses of resin that have the appearance of wads of gum
stuck to the sides of the trunk. These are the result of the
tree's attempt to expel invading beetles. Photos of
pitch tubes are included on this page.
To protect your property, check all the
pines—ponderosa, lodgepole, and limber—for pitch tubes.
Checking in fall after October 1 gives you more time to
remove and treat beetle-killed trees for use as firewood. If
you find beetle-killed trees in April or May, the only
option may be to cut and dispose of the wood.
Other evidence of an attack includes
yellowing or browning of the needles on the entire tree.
However, this indication may not be obvious until it’s too
late to remove infected trees.
If you find pitch tubes and the tree shows
sign of yellowing in spring, the tree needs to be cut. Pitch
tubes alone show only that the tree was attacked. Healthy
trees often ward off invasion. Do not cut otherwise healthy
trees with pitch tubes without inspecting them for tunneling
and live beetles or larvae. Information on how to do that is
given in the section on “Free Inspections” below.
Trees attacked by beetles die from a
fungus carried by the beetles called “blue stain fungus.” It
spreads very quickly throughout the inner tree, stopping the
flow of sap and effectively killing the tree. The offspring
of the beetles that attacked the tree the previous year tunnel under the bark and can gird the
tree, with the same outcome.
An
excellent overview of mountain pine beetles is found on
Colorado State
University’s mountain pine beetle
website.
Treating Beetle-kill Trees
If a tree that has been attacked is not cut
down and disposed of or treated, a new generation of adult beetles will
emerge from beneath the bark and fly in swarms to attack
healthy pine trees. These flights begin in July.
The beetles may attack adjacent trees on your
property or nearby trees on your neighbor’s land. They may
fly as far as five miles before attacking other trees.
One tree
left untreated can result in the death of several other trees,
and that’s why it's the landowner’s responsibility to cut
down and treat beetle-killed trees. Removal is required by
state statute, county ordinance, and
local ordinance. For information
regarding enforcement of the state and county laws, visit the
Larimer County Forestry
website.
Trees attacked by beetles must be cut down
and disposed of or treated by July 1 to assure the adult beetles do not
fly to other trees.
The Tree
Board recommends doing so by June 15. Reliable local
tree services can be of assistance in cutting and disposing
of beetle-kill trees. Check the phone book for those
services.
If you decide to do it yourself, cut down the
tree, strip the limbs off, and treat the trunk to kill
beetles before they emerge. One labor-intensive treatment is
to strip the bark from all infected areas, exposing the beetles and killing them.
Use a
drawknife or chain saw attachment to strip the bark.
A less
effective alternative method utilizes the heat from solar
radiation to kill the beetles. Trees must be cut early,
preferably in the fall, and the
weather must cooperate. For
information on this treatment, see the Colorado State Forest
Service’s website on
solar treatment.
The best alternative may be to dispose of the
tree.
The Town of Estes Park's
Air Curtain Burner is currently open from Monday
through Friday, 8 a.m. to 4 p.m. and is available for beetle
tree disposal FREE OF CHARGE to Estes Valley Residents.
The Air Curtain Burner site is located at 666 Elm Road, past
Waste Management on the right side of the road; access is
through the yellow gates. Trees must be properly
prepared - stripped of all branches and cut into pieces no
longer than eight feet - and transported to the site.
Note that trees with pitch tubes that have
brown, brittle needles or no needles were killed by beetles
in previous years. They may be taken for firewood or left as
wildlife trees. Removal and treatment is not required.
Free Inspections Available
As a property owner, you should check your
pine trees for beetle attacks in October and again in April. If a
tree has pitch tubes and is yellowing in spring, you can be
certain it needs to be cut and disposed of or treated.
Not all trees that have pitch tubes die.
Healthy trees can sometimes reject minor attacks by beetles.
The resin exuding from pitch holes is the tree’s attempt to
reject the beetles. If the tree shows no other signs of
imminent death, you should check for tunneling, live
beetles, or blue stain under the bark before cutting it
down.
You can do this yourself by using a hatchet
or chisel to remove bark at the site of pitch tubes. Beetles
tend to burrow up from these entry points. Remove a section
of bark about four inches square to the left of the pitch
tube. Indications of a successful attack are tunnels bored
by the beetles and blue stain in the wood. Following tunnels
often reveals live larvae or adult beetles.
If you
prefer, you can request a free inspection by a volunteer
trained in confirming successful beetle attacks on trees
with pitch tubes. The number of trained volunteers is
limited, so it is not possible at this time for them to
canvas entire properties.
To arrange a free inspection, call the Town
of Estes Park Public Works Department at 577-3588. Other sources of
inspections include the Larimer County Forester at 498-5765
or the Colorado State Forest Service at 491-8660, or local
tree service companies. There is a
fee for services from these agencies.
Preventing Beetle Attacks
You can protect especially valuable trees by preventive
spraying. The spraying must be done between the middle of
May and the end of June to be effective. If you spray
earlier, the spray may lose its potency. Spraying later than
the end of June may be too late to kill the beetles before
they fly.
Smaller trees are not usually attacked by
beetles, although they can be. The most likely targets are
mature trees with trunks of 12 inches in diameter or larger.
The trunks need to be sprayed to a height of 30 feet. You
should have your most valuable trees sprayed every year. The value
you place on them may have to do with size, nearness to your
home, the character of the tree, or family history, along
with other personal factors. Charges may range from
$15-$20 per tree.
A number
of companies spray in the Estes Valley, using either
carbaryl or permethrin, both proven chemicals. The
companies listed below are licensed by the Colorado
Department of Argricultue.
Horizon
Forestry, 577-6154, Boulder, CO
Kincade
Tree Company, 484-8733, Fort Collins, CO
Preventive Tree Spraying, Inc., 970-468-1254,
Dillon, CO
Swingle
Tree & Lawn Services, 663-2071, Fort Collins, CO
Cate
Brothers, Inc., 970-587-0719
It is
important to make arrangements for spraying well in advance.
These companies are very busy and the timeframe for
effective spraying is very short.
For more
information, visit the Colorado State Forest Service website
on
preventive spraying.
A relatively new
alternative to spraying is BeetleBlock, utilizing Verbenone,
a synthetic pheromone. Controlled-release packets are
attached to trees. They release a replica of the
pheromones beetles emit when a tree has reached its
capacity, thus repelling entry by other beetles. The
cost for protecting a tree with BeetleBlock is similar to
the cost of spraying. For more information, contact
AgBio, Inc. in Westminster, CO at 303-469-9221.
Douglas-fir
Beetles
These beetles attack only Douglas-firs, but
like mountain pine beetles, they carry the blue stain fungus
and affect trees in the same way. However, there are
significant differences.
Douglas-firs do not exhibit the same symptoms
as pines attacked by beetles. There are normally no pitch
tubes on the trunk, the best evidence of a beetle attack in
pines. Instead the infested tree simply turns from green to
lighter green to yellow and then to red. Very fine sawdust
can often be found in bark crevices at the base of the trunk
to help confirm the cause.
Most importantly, these beetles fly much
earlier. They emerge shortly after Memorial Day. Infected
trees must be treated before that time. Treatment is the
same as the treatment for beetle-kill pines, described
above.
Shortly after the Lawn Lake Flood, many
Douglas-firs were attacked by beetles. With due diligence in
taking care of infested trees, the Estes Valley has had only
a few losses during the past ten years. We hope to continue
these efforts. Free inspections of suspected Douglas-fir
beetle attacks are available by calling the numbers listed
above.
Ips Beetles
Another species of bark beetle, ips beetles
generally attack young trees, particularly newly planted
saplings. They also feed on residue in slash piles,
windblown trees, and other forest debris. Those food sources
should be disposed of quickly to prevent an outbreak of ips
beetles.
Attacks
by ips beetles can occur anytime during the growing season,
April through October. They have several life cycles in a
year, thus control and prevention are more complicated than
they are for mountain pine beetle. The
Colorado State Forest
Service
has an
overview of the ips beetle that you may find helpful.
Spruce Bark
Beetles
Entire stands of spruce trees in parts of
Colorado have been devastated by spruce bark beetles,
especially areas with widespread windblown downfall.
Fortunately, the Estes Valley has been spared
any attacks to its spruce trees and no precautions are
necessary at this time.
Red Spider Mites
These pests are common on many ornamental
plants, shrubs, and trees. In the Estes Valley, they occur
generally after pines have been sprayed for beetles for
several years in a row. Continual spraying kills the natural
enemies of the mites but not the mites.
The evidence of red spider mite infestation
is the sudden appearance of spider webbing at the base of
pine needles. The mites can be removed with a forceful spray
of water from a garden hose. If you cannot reach the top
branches with enough pressure, spraying with Kethane or a
similar chemical may be necessary. Contact the tree sprayers
listed in the section above on preventing pine beetle
attacks.
Dwarf Mistletoe
Dwarf mistletoe is a parasite that invades
trees, particularly ponderosa and lodgepole pines in our
area. Douglas-firs are also susceptible. Mistletoe kills
trees by taking the water and nutrients they need to live.
Trees of any size can be infected.
The visible part of dwarf mistletoe consists
of clumps of segmented shoots on the tree’s branches. The
shoots are yellowish green to rust in color, .5 to six
inches long, .25 inch or less in diameter, and can be found
from the lowest branches to the top of the tree. The shoots
have no leaves and exist only for reproduction purposes.
The main part of the plant lives beneath the
tree’s bark. Part of the root system extends into the phloem
where it takes nutrients from the host tree. A second part
is embedded in the xylem where it takes water from the tree.
Another sign of dwarf mistletoe is the
appearance of witch’s broom, a malformed clump of branches
on the tree caused by the parasite. These take many forms,
but most are dense, circular masses of twisted branches and
needles that are obviously not typical growth. The visible
part of the mistletoe plant will be found on these infected
branches.
We’ll discuss how trees are infected, how to
assess the infection, and management of mistletoe.
How Trees Are Infected
The plant takes hold when a very tiny, sticky
seed finds its way to the needles or branches of the host
tree. Sometime in August, seeds are explosively discharged
from seed pods on nearby infected trees, shooting out at
speeds up to 60 mph and as far as 30 feet. They can be
carried even farther by the wind. Seeds from the topmost
branches of tall trees can easily travel 100 feet or more.
Seeds also stick to birds and squirrels and are carried to
other trees by them.
Seeds typically germinate on lower branches
first. Because lower branches are generally more heavily
infected, one of the signs of mistletoe is the browning of
top branches. The parasite saps the water and nutrients
before they can reach the top of the tree.
Once the seed is on a new host tree, it
germinates and takes root within the tree, spreading down
the branches into the trunk and eventually killing the tree
by absorbing the water the tree is collecting and the
nutrients it is producing for its own growth. It may be as
long as two to three years before the shoots appear and five
to six years before the mistletoe matures and reproduces.
Trees infected with mistletoe are weakened
and become more likely to succumb to drought conditions and
beetle attacks. The death of many pines during the several
years of drought in Colorado can be attributed to dwarf
mistletoe. The Cow Creek area in Rocky Mountain National
Park is heavily infested, as are some areas in the Estes
Valley.
Assessing Mistletoe Infected Trees
There is a fairly simple method for assessing
the condition of a tree infected by mistletoe. First,
visually divide the tree into thirds from top to bottom.
Then give points to each section as follows
(binoculars will be a help with tall trees):
0 = no visible infection
1 = 50 percent or less of the branches have visible
infection
2 = more than 50 percent of the branches have visible
infection
Then add the points for each third to derive
the rating for the tree.
1-2 = lightly infected
3-4 = moderately infected
5-6 = severely infected
Severly infected trees should be cut down.
There is no effective management of the infestation when it
is at this stage, and these trees will continue to spread
the parasite to nearby trees until they die. Fifty percent
of severely infected trees with a diameter greater than nine
inches die within ten years. They should be cut down before
August to avoid further infections. The mistletoe dies
immediately, so no further treatment of the wood is
necessary.
Moderately and lightly infected trees can be
pruned to control the parasite, and that’s what we’ll
discuss next.
Managing Mistletoe
There is no known “cure” for mistletoe. No
chemical has been developed that will kill the parasite
without killing the host. Some companies offer mistletoe
spraying, but it is only a control measure for the spreading
of seeds and must be timed to coincide with the seed pods’
maturity. It does not kill the parasite or otherwise control
its growth.
Mistletoe can be managed effectively to
prolong the life of a tree, if the tree is not too heavily
infected. Caught early enough it can be eliminated from the
tree. Yearly inspection of the trees on your property can
help you catch an infestation in time to save a tree. The
growths are relatively easy to spot on lower branches.
Binoculars can help with the inspection of higher branches.
Control consists of trimming off infected
branches at the trunk. Once the branch is cut, the mistletoe
dies, and no further treatment is necessary. Branches can be
used for firewood or disposed of without concern. The wound
where the branch was removed need not be painted or covered
with any substance. It should be allowed to recover
naturally.
Trimming should be done after the first of
October to allow wounds to heal over the winter months. If
wounds are bleeding sap during the pine beetle flight times,
the resin may attract an attack on the tree or its
neighbors.
Trimming is a “Catch-22” situation. The limb
or branch that is trimmed was providing part of the
sustenance the tree needs. Removal of too many branches will
weaken the tree and open it to beetle attack. Leave at least
40 percent of the branches on the tree, even if some are
infected. Repeat the pruning every two to four years.
Lightly infected trees may live for many
years, perhaps much of their natural life span, if treated
in this manner. Moderately infected trees are more likely to
have shorter lifespans, often falling prey to drought or
beetles due to their weakened condition. The value of the
tree should determine whether pruning is worth a try for
moderately infected trees. Protecting nearby healthy trees
must weigh in the decision.
Finally, you can further manage mistletoe by
replacing removed trees with other species. Mistletoe is
specific to each tree species. If a ponderosa was removed,
you might consider replacing it with a Douglas-fir or a
limber pine.
In planning landscaping, diversity should be
considered an essential element of the design, one that
protects from the loss of many trees to a single,
species-specific infestation or disease.
For more
information, see the Colorado State University online
publication on
dwarf mistletoe.
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