Page 20
— Property Management Quarterly — February 2015
L
ast year brought some unex-
pected surprises and exciting
opportunities. As we move into
the new year, Swingle is pre-
dicting emerald ash borer and
the November 2014 freeze will have a
major impact on Colorado landscapes.
Therefore it’s vital that property own-
ers and managers think about how
their community will be affected.
Emerald ash borer.
Discovered in Sep-
tember 2013, emer-
ald ash borer is a
wood-boring insect
that attacks all ash
trees growing in
Colorado. At its most
infant stage (larvae),
the insect will bore
into the tree, mak-
ing “S” shaped gal-
leries just below the
bark.The damage
caused by the insect
deprives the tree of
much-needed water
and nutrients. EAB has yet to be found
outside of Boulder, but during this past
summer some important develop-
ments transpired.
First, the entire city of Boulder is now
thought to be infested with EAB and
under quarantine through the Colo-
rado Department of Agriculture. Boul-
der County does not have the waste
facilities for wood debris from infested
trees, so all wood must be taken for
disposal to either Larimer,Weld or Jef-
ferson counties, which are currently
under quarantine. Additionally, Boulder
is a highly mobile community with a
busy university and daily commuter
traffic.This leads to the likelihood of
the insect breaching the quarantine
area.
Second, many trees throughout
several city blocks are symptomatic
of borer infestation and sadly have
begun dying. Symptoms include dead
branches, thinning leaves at the top of
the tree, sprout growth near the base
and “D” shaped exit holes present on
the bark.
It’s estimated that EAB has been
feeding on Boulder ash trees for six
years. EAB is unquestionably the worst
urban landscape disaster to reach
North America and is now ready to
take off in Northern Colorado commu-
nities. EAB has killed over 50 million
trees, and kills 99 percent of the ash
trees it comes in contact with.
When EAB was first discovered in
Michigan in 2002, the federal govern-
ment tried to eradicate the insect by
taking down healthy trees around
infested areas.This, however, was
unsuccessful.There is no proven way
to stop the spread. Every year since
2002, the insect has spread. It is now
in 21 states, but eventually will end up
in all 48 continental states because,
while the insect flies less than a mile
per year, it is an excellent hitchhiker,
traveling across state lines on firewood
and vehicles.The insect is stealth and
by the time its presence is known, it’s
likely too late to treat the tree.
The next discovery will certainly be
within the next 18 months. If the borer
is discovered outside of Boulder, imme-
diate action will be needed to save
Colorado ash trees. Property mangers
should work with a certified expert to
identify ash trees on their property,
evaluate for infestation and receive
treatment options. Any detection of
EAB symptoms should be reported to
the Colorado Department of Agricul-
ture.
November freeze.
Mild temperatures
during the fall of 2014 came to an
abrupt end in mid-November.The high
temperature Nov. 10 was 64 degrees
Fahrenheit.The night of Nov. 12, the
recorded low temperature was -13
degrees Fahrenheit.This represents a
77-degree change in temperature in
three days – the third-greatest tem-
perature drop ever recorded in Denver
since 1872.
When the freeze hit, many plants
still had foliage, and even more had
not fully hardened off for winter.The
process of hardening off is when the
sugar concentration of the cells chang-
es in the foliage – essentially lowering
the freeze temperature.The plant cells
were not far enough along in the pro-
cess, and simply froze and ruptured,
similar to frozen pipes.The freeze dis-
rupts the water-conducting tissues in
the tree or shrub, desiccating the plant
tissues in the dormant season.
Initially we thought plant injury
would not appear until spring 2015.
But after just a few weeks, the south
sides of our spruce and pines turned
a bleached, straw color and junipers
turned bronze. Many shrubs, fruit trees
and, especially, roses are also showing
freeze damage.The twigs are brown
and shriveling.
Brown leaves still clinging to trees
may indicate damage. A skilled arbor-
ist can check the buds and the tissue
below the bark of young shoots to see
if the plant is viable. Managers should
have dead twigs and branches pruned
and provide consistent watering to
the landscape, even during the winter
months.We will have to wait for spring
to see how these damaged plants
respond.What can you expect? A
continual loss of foliage on evergreens
throughout the spring, and leafy plants
may fail to leaf out or do so sporadi-
cally.
Pine wilt nematode.
In states just east
of Colorado, thousands of Scots and
Austrian pines have been lost due to
pine wilt.This tiny, wood-boring insect
(pine sawyer) spreads a wormlike
animal, called a nematode, to healthy
pine trees.The nematode multiplies
and clogs up water-conducting tissues
in the tree.The insect is more stealth
than EAB, and typically infestation is
difficult to recognize until the tree rap-
idly dies in the late summer or early
fall. Even when the tree dies, there are
no visible signs of insects, nematodes
or disease.The insect has been found
in areas of Colorado such as Lamar,
Greeley, Fort Collins, Parker, Aurora,
Centennial, Highlands Ranch, Den-
ver, Englewood, Littleton, Longmont,
Loveland and Grand Junction. Pine wilt
predominantly affects Austrian, Scotch
and mugho pine trees.
In 2012, during an unusually hot
summer, experts saw an uptick in tree
mortality.The good news is that 2013
and 2014 both had moderate summer
temperatures, as well as above normal
rainfall, which dampened the pine
wilt nematode’s destruction. In 2014,
Swingle did diagnose a few trees with
pine wilt, so the nematode is still out
there. If there is a hot spring, there is
the potential to see many pines die in
the fall of 2015.
Japanese beetle.
For those from the
eastern United States, you might be
very familiar with this insect, because
its origination began there. Japanese
beetles need consistent soil moisture
to mature, especially in the winter.
During the 2013 and 2014 winters,
Colorado had an abundance of mois-
ture, which resulted in an uptick of
Japanese beetle activity in the 2014
summer.
Property managers and owners
should look for green beetles feeding
on the foliage of garden plants and
vegetation.They tend to feed on roses,
Virginia creeper (vine), linden trees and
many other ornamentals. Japanese
beetles won’t kill your plants, but will
make them very unsightly.The avail-
able spray treatment for the Japanese
beetle won’t eradicate the insect,
but can help to control it.Two sprays
should adequately manage the insect
because it stops feeding on foliage in
early August. If this winter continues
with consistent moisture, be on the
lookout for Japanese beetles in early
July.
s
Vendor Trends
Steve Geist
Senior consulting
arborist, Swingle
Lawn, Tree and
Landscape Care,
Denver
Swingle
The “S” sign an emerald ash borer makes when it has infected a tree
Swingle
Pine wilt nematode infects Scots and Austrian pines.
