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Disease and Insect Update
Tree Diseases and Preventative Treatments
By Brad Hatfield-ISA, Kansas Certified Arborist
Dutch Elm Disease-
All American and other native Elms are susceptible to this disease. In the course of our
work,we see many Elms infected and dying every year. We have been utilizing a macro-injection
system and the chemical Arbotect to treat Elms preventatively with great success. Elm trees have to be injected
every two years with the fungicide Arbotect.Trees displaying widespread signs of infection are generally not good
candidates for treatment.The fungicide only stays active and working for a two year period, at which time the tree
will need to be injected again.
A general wilting or yellowing in the canopy, followed by a distinct flagging of leaves.
Leaves brown and some hang on branches while others are quickly shed.
In the early stage, it is possible to save trees by scribing bark, pruning out infected limbs
and injecting with Arbotect. If the tree is infected by root grafting to another infected
elm, it cannot be saved. Infected Elms showing symptoms throughout the canopy or more
than 10-15 percent are a poor risk for treatment.
(Pictures courtesy of RainbowTree)
Above left-flagging and yellowing of leaves in American Elm. Above middle-Bark removed to show streaking in
sapwood.Above right-Elm Beetle, responsible for spreading Dutch Elm Disease.
of Rainbow Tree)
The picture above illustrates why infected Elms should be removed promptly and not be allowed to over -winter, or
infected wood kept and stored as firewood.This provides a breeding habitat and a way for overwintering eggs to
hatch and release a new generation of beetles to infect other trees.Dutch Elm Disease can be spread from root
grafting to adjacent trees. There is also a distinct possibility that the disease can be spread from
pruning tools or climbing spikes. Consider dormant pruning on your Elms. If you have a specimen Elm or a
significant amount of Elms on your property, consider preventative treatment.
Oak Wilt has received a great deal of attention in the news lately, but is a disease that Arborists see every year on a limited scale.
Contrary to popular belief, the vast majority of Oak Wilt is found in naturalized
stands of Red Oak, not in area neighborhoods. The symptoms of Oak Wilt are very distinct!
Above left-Distinct "half leaf" symptom of Oak Wilt. Above Middle-Streaking in Sapwood and leaf symptom.
Above right-Nitidulid beetle-They feed on fungal spore mats and can spread the disease via pruning cuts or
wounds.(Pictures courtesy of Kansas State University)
Leaves are quickly shed, caused by plugging in the vascular portion of wood. The leaves themselves are
often a helpful diagnostic aid. Oak wilt infected trees have a very distinct "half-leaf" symptom and also appear
waterlogged. The streaking in sapwood usually associated with Wilt diseases is often absent in Oak Wilt infected
wood.When the temperatures go up, the fungus retreats to the lower portion of the stem.The only way to get a
complete diagnosis is to send leaf samples and cuttings of 1-2 inch wood to the Extension Plant Pathology Lab
for confirmation.Oak Wilt can be difficult to culture in the lab, so you can't always get a 100% confirmation.
We use a macro-injection system and Alamo fungicide to treat at-risk trees. Infected Red Oaks generally do not
respond well because of vascular plugging, a defensive internal reaction to the presence of the attacking fungus.
Trees close to Oak Wilt infection sites should be treated preventatively and you must trench between
infected trees or in areas with multiple infected/at-risk trees to sever root graft. The most common way this disease
spreads ist hrough root grafting.
Consider dormant pruning on your Oak trees, particularly Red Oaks.
Do not allow anyone wearing climbing spikes into your Oak trees. Although Oak Wilt can be
spread by climbing spikes and pruning equipment, the most typical spread is through root grafting,
between trees with a shared root space. Nitidulid beetles can also spread the disease.
These beetles feed on fungal spore mats in infected trees.This type of beetle would be attracted
to wounds and pruning cuts. This disease can spread quickly in areas dominated by Red Oak.
Map showing areas of Oak Wilt infection(USDA Forest Service)
Hypoxylon Canker of Oaks
As an Arborist in the Kansas City area, I have become accustomed to seeing many varieties of diseases and pests
afflicting area trees. Our company is often called upon to diagnose and treat these problems. There is a fungal
canker known as Hypoxylon (Hypoxylon atropunctatum) affecting Oak trees in the metro area, particularly Red
Oaks. Although it does not get a great deal of attention, this aggressive canker causes the death of large diameter
limbs and can ultimately kill Oak trees.
This is not a new , exotic pathogen. Hypoxolyn Canker is visible in Oak trees all around us. Many large size limbs
or stems that die out can be attributed to this canker. Hypoxylon Canker is naturally occurring in forested areas.
It is becoming much more common in urban sites when people cause damage to roots and root zones.
Trees infected with or dying of Hypoxylon are often misdiagnosed as having Oak Wilt.
You have to be able to recognize the symptoms, which are very distinct! According to Dr. Ned Tisserat, former
Kansas State Director of Plant Pathology, Hypoxylon Canker is latent, or dormant in many Oaks. The tree is able
to function and live with the fungal infection until it becomes severely stressed or damaged. At that time, when
energy levels are low, the fungal canker becomes active and spreads.
Photos of Hypoxylon Canker on Oaks-Far left and middle, two Red Oaks that died from Hypoxylon. Far right, a
very large White Oak dying from Hypoxylon infection.
The most obvious early symptom of Hypoxylon is the sloughing off of bark. The bark falls or peels off to expose a
dusty- looking brown canker. This early stage of the canker is an active stroma,which bears brown masses called
conidia. The one-celled conidia are scattered by the wind and can cause infection to other trees. The active canker
soon hardens, changing color to silver or grey and as the sexual stage progresses, begins to produce black spores.
These spores can be spread by rain or insect activity to other branches of the same tree or to other individual
trees. Cankers can easily spread 3 feet in one season of growth. Large Red Oak trees can die within one or two
years of displaying symptoms of infection. White Oaks seem to be more resistant to the fungus, but I witnessed a
very large, mature White Oak dying of Hypoxylon infection in Missouri last year and have seen other White Oaks affected in the past.
There is no legitimate or effective control for Hypoxylon Canker. The fungus remains active on dead wood, so
infected or suspect wood should never be kept or stored. Infected limbs or stems can be pruned out, but use good
judgement based on percentage of unaffected canopy. Even after pruning, there is a likelihood of canker spread
and dieback. Trees that have not lost more than 10-15 percent of canopy would benefit from supplemental watering in dry
conditions and aeration/fertilization. Avoid root injury and monitor trees closely that have
been impacted by construction, soilcompaction or drought stress. It is possible that this
fungus could enter fresh pruning cuts and or injury by climbing spikes and could be spread from
spikes or pruning tools. Dormant pruning is the safest way to go on Oak trees.
It is important to note that the majority of trees I have seen infected with Hypoxylon have been impacted by
construction activities. Root injury, in my opinion, is the number one way for this fungus to overcome the natural
boundaries and defenses that Oaks possess.
Avoid digging in or disturbing the root zones of any trees, particularly Oaks. If workers do any
trenching or digging under the dripline of your trees-Take Pictures! Document the size and location of any root
disturbance, write down the date, the name of the company and how long the job took. Trees do not always show
symptoms of root injury right away. Cutting or damaging roots can weaken any tree, leaving it vulnerable to the
first opportunistic pathogen that happens to be in the neighborhood. Utilities and contractors will deny
any damage to your tree or roots, will tell you they have a "special" way of doing the work that doesn't hurt trees
and will hire some type of "tree guy" that will try to find something else wrong with your tree! If you have any
doubts about the condition of your trees, contact an Arborist!
Although Pine Wilt is not a disease, it has become so widespread, we feel it should be included.
*We are starting to see more Austrian Pines infected in Kansas City.
**Kansas State University Plant Pathology confirmed our suspicions, Pine Wilt on Austrian Pine is on the rise, with
a higher rate of positive identification in the KSU Lab.
If you drive or walk around the Kansas City area and look closely at the surrounding landscape, you will see
wilting Pines. It seems that most neighborhoods are affected . I have been responding to an extremely high
number of diagnostic calls that are Pine related. Unfortunately, we are now seeing more Austrian Pines affected by Pine Wilt. Pine Wilt has been active in the Midwest for the last twenty years or so and until recently, roughly 90% of
Pines killed in the Midwest have been Scotch Pines. Pine Wilt is not new to our area, but it appears to be more
common and widespread, with Austrian Pines now being affected.
Difficulties with Pine trees is a common experience in the Midwest. It is important to look at the big picture,
especially when dealing with Scotch Pines. We have taken Scotch and Austrian Pine trees, suited to temperatures
and environmental conditions in Europe, and have planted them extensively here in the Midwest. They have done
fairly well and in some cases done well for great periods of time. But now we have some events occurring together
that are killing these trees at an alarming rate.
Pictured above-Pine Wilt in Overland Park
The explosive summer heat and the droughts we have been experiencing play a role in the demise of Scotch and Austrian Pines.
These environmental stresses that Pines are enduring create an opportunityfor any specific pathogen. In the case
of Pine Wilt, it starts with the Pine Sawyer Beetle feeding on Pine twigs. The feeding itself causes little damage.
However, the Pine Sawyer carries a microscopic, worm-like creature called a nematode in its trachea. When
feeding, the Pine Sawyers wounds create an entry for the nematode. The nematode enters the healthy Pine.
Resistant Pines cause the nematode to die out. In susceptible Pines, the nematode begins to feed on living cells in
the resin canals. As the nematodes feed and multiply, the resin canals become clogged, which eventually stops the
flow of water in the tree.When this happens, the wilt symptoms begin to develop and the tree begins to die.
In addition, the
dying Pines attract bark beetles, which carry a blue-stain fungi.
As the bark beetles bore into the dying pines, the nematodes begin to multiply by feeding on the blue-stain fungi,
supplied by the bark beetles. Pines infected with the Pine Wilt nematode typically die within a period of a few weeks,but some
can linger for a month or two. Most of the Scotch Pines affected are over 10 years of age.
Pictures above left-Beetle activity indicated by close up of borer holes. Right-Blue stain fungi on affected Scotch
Above-Picture of Pine Wilt Nematode
*At this time, there are some chemicals being marketed for treating Scotch & Austrian Pines preventatively.
Trees must be injected with chemicals prior to infection.
This is a relatively new process, can be expensive and the best we have heard is
70% to 80% control. We will not endorse/use it until costs come down and we see more
data or a higher percentage control rate.
important management tool for control is sanitation. Dead Pines
breeding grounds for beetles/nematodes. Remove dead or dying trees as soon as possible and do not store any of
this wood as firewood. Remove tree completely and grind out stumps. There is some debate over root graft spread
of nematodes, so you may have to consider trenching in areas heavily planted with Scotch Pine. Even a single
infected Pine tree left standing can become an infection center that will devastate other Pines nearby.
Consider planting other less problem prone trees. Eastern Red Cedar, Juniper,
Hemlock and Baldcypress do well in our area and have a much better
life expectancy. We are must now accept that Scotch, Austrian and White Pinecan get Pine Wilt and each have
their own problematic baggage.
Spruce trees are an acceptable replacement, but do not always thrive in our environment.
If you are looking for smaller sized trees for screening, try something native like a Redbud, Serviceberry or
plant one of the many varieties of Crabapple.
Pine Needle Fungus
VanBooven Arborists are generally dealing with three different types of Pine Needle fungus, Sphaeropsis/Diplodia,
Dothistroma and Brown Spot. Of the three, Sphaeropsis is the most
serious, with Scotch and Austrian Pines being severely damaged or killed over time.
Sphaeropsis Tip Blight
This fungus is a problem for Austrian and Scotch Pine, particularly on older or mature trees.
Tip Blight stunts and kills new growth on these Pines. If not treated, Tip Blight will cause the gradual death of large limbs
and over time the entire tree may decline and die.
The fungus overwinters on cones, branches and dead tips, with most infection occuring on the new growth (tips) in
the Spring. The crucial factors in controlling this problem is timing your fungicide sprays to protect the susceptible
new growth and accurate, thorough spray coverage.Sphaeropsis is very common in the Kansas City metro area.
(Photographs courtesy of US Forest Sevice)
Left-Austrian Pine infected with Tip Blight, Middle- shows pycnidia on cones, Right-Map of states affected by
Tip Blight are marked in grey.
Dothistroma Needle Blight
Dothistroma affects mainly Austrian Pine in the Kansas City area.
Symptoms are very distinct, with a heavy shedding / browning of inner needles and heavy spotting and or banding
of individual needles. The early shedding of needles needed by the Pines can lead to loss of health and repeated
loss of foliage by continued infection(over several years) can lead to severe decline or death of Pines.
Dothistroma infection of Austrian Pine is very common in the Kansas City area, but can be controlled by proper
applications of fingicide.
(Left and right photo courtesy of US Forest Service, middle Kansas State University)
Left-Infected Pine shedding needles, Middle shows spotting/banding of diseased needles, Map of states affected,
Brown Spot Fungus
Scotch Pines in the Kansas City area are fairly susceptible to Brown Spot, but Brown Spot infection is not as
widespread as Tip Blight or Dothistroma. Symptoms are similar to Dothistroma but a close inspection of needles
will reveal black fruiting bodies of the fungus on needles, as opposed to the spotting/banding of Dothistroma.
Infected Pines should be treated with a fungicide spray.
(photo courtesy of Kansas State University)
Picture above shows very distinct symptoms of Brown Spot.
If you have a question about your trees, we have an answer. To speak with a Certified Arborist,
please contact us at 913-403-TREE.
VanBooven Tree Care Home Page
VanBooven Professional Tree Maintenance
Tips For Hiring An Arborist
Disease and Insect Update