Tree Integrated Pest Management

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Tree Integrated Pest Management

Tree Diversity Minimizes Pest Problems

July 8, 2014 · No Comments · Abiotic, Insect Pest, Plant Disease

A diverse Christmas tree planting.

A diverse Christmas tree planting in Upstate New York.

A large planting of a single species is easier to manage and harvest but can be a windfall for pests. Monocultures allow insects and disease to expand rapidly as the pest can move unimpeded from one plant to another. After the devastation that occurred in community forests with streets lined exclusively with American Chestnuts (Chestnut Blight) and American Elms (Dutch Elm Disease), planting a diversified mixture of trees is now the standard practice among municipalities.

Dead Fraser fir with healthy Canaan Fir foreground and turkish fir behind. side.

Dead Fraser fir with healthy Canaan Fir foreground and Turkish fir behind.

Many nursery and Christmas tree growers also know the advantages of growing a variety of species.   They’ll choose tree species to fit their different environments on their farm.  Then just like the smart investor who has diverse portfolio to minimize risks in the future, diverse plantings can prevent pests from moving in and wiping out all the trees.  Even landscape designers when working with customers who envision a planting of a single species will often try to specify a mixture of similar species to increase resilience.

There's increased interest in Turkish firs such as this example of Abies bornmuelleriana because of it's root rot resistance.

There’s increased interest in Turkish firs such as this example of Abies bornmuelleriana because of it’s root rot resistance.

Having a diverse planting works because most insects and diseases have preferences for the host species they feed upon.  Many simply cannot live on a different genus, for example it is rare to find an insect or disease that lives on both fir and spruce trees.  In addition certain sites on a farm or landscape may be more conducive to one species over another.   For example if  a species is mis-matched on a site with soil conditions it cannot tolerate, then the whole planting may succumb to a root rot.

Growers taking notes on new tree species they may want to add to their plantings at Cornell Plantations.

Growers taking notes on new tree species they may want to add to their plantings while at Cornell Plantations.

Cornell Plantations is one place where you can experience and compare a wide variety of deciduous trees and conifers.   Although their plantings extend over several acres on campus, a concentration of conifers can be found at the Kienzle Overlook. .  At this website you can find a list of the 80 + conifers species that are in that planting.

Phil Syphrit

Phil Syphrit

Phil Syphrit is the curator of this collection and can help answer questions on some of these unusual conifers if you are interested in adding them to your plantings.


Pine Sawflies

June 12, 2014 · 1 Comment · Insect Pest

Notice needle damage on pine trees?  Look close.  It may be caused by conifer-feeding sawflies.

Sawflies feeding on Scotch pine

Sawflies feeding on Scotch pine

Sawflies? As larvae they look caterpillars which might develop into moths, their name implies they’ll be flies, but they actually become non-stinging wasps as adults. And the saw? As adult wasps the females cut slits in pine needles with saw-like structures on the tip of their abdomens and lay eggs into these openings.

Checkout the synchronized movement they make to deter predators!

Although there are several species of sawflies that can be seen on conifers the gray-green European Pine Sawfly (Neodiprion sertifer) is represented in this post. 

European pine sawfly group

European pine sawfly group

Sawfly Management

  • Monitor to detect infestations before they reach a size that can cause significant needle loss.
  • Know that sawfly larvae are attractive as food to parasites and predators and are usually kept in check by these natural enemies.
  • If a small outbreak occurs they can often be handpicked, or pruned out and destroyed.
  • For rare situations where the population of sawflies are high insecticides labeled for their control can be used.
individual pine sawfly

Pine sawfly larvae


Winter Injury

May 7, 2014 · No Comments · Abiotic


What a winter!  It was long and cold.  We experienced a couple of polar vortex events and subzero Fahrenheit temperatures were common.

WInter Injury visible on the Nordmann fir trees in the foreground.

Winter injury symptoms of needle browning visible in the foreground on Nordmann fir trees.

Evergreen trees and conifers were impacted by the extreme conditions. The symptoms of the winter injury has been showing up on evergreen needles for the last month or so.  The damage is appearing as needle browning– sometimes whole needles and sometimes just the tips.

Some of the species affected this spring:

Winter Injury symptoms is common Nordmann firs.

Winter Injury symptoms is common Nordmann firs.

Grand fir trees are showing winter injury symptoms in many parts of NY.

Grand fir trees are also showing winter injury symptoms in many parts of NY.







Douglas fir trees that have swiss needlecast infections were most prone to winter injury.  Some un-treated landscape trees are mostly brown.

Douglas fir trees that have Swiss needlecast infections were most prone to winter injury.







Untreated Douglas fir trees in in the landscape. Suffering from a combination of Swiss needlecast and winter injury

Untreated Douglas fir trees in in the landscape. Suffering from a combination of Swiss needlecast and winter injury.






Concolor fir trees planted in sites with poor drainage were susceptible to winter injury.

Concolor fir trees planted in sites with poor drainage were susceptible to winter injury.

The good news is that in almost every case the buds are fine!  So the new growth will soon help cover up the brown, winter injured needles. Be sure the soil conditions are optimum to maximize growth.  Adjust pH and fertilize as needed.

And one more…

A different type of injury that occurred during this winter.  Lower branch dieback from rodent feeding on the branch bark.

A different type of injury that occurred during this winter. Lower branch dieback from rabbits and/or meadow mice feeding on bark. (They apparently have their favorites.  In this mixed planting they only munched on the Korean fir trees.)










Check for Fir Rust Disease

October 4, 2013 · 1 Comment · Plant Disease

Fir Broom rust is becoming more common in New York as the number of fir tree plantings increase.  This disease produces a proliferation of shoots “witches brooms” that can make the tree unsalable.

Severe Fir Broom Rust can cause losses for growers.

The fall and the upcoming sale season, are a good times to see if it is present in the field.  When taking off the bottom limbs of trees be sure to take notice if any brooms are present. Also when the trees come in during harvest season keep an eye out.

It can be difficult to detect the small “brooms” at first

Hidden broom

Because the affected growth is shorter than the surrounding branches it is often hidden.

The disease often shows up on the lower branches first where the rust fungus benefits from increased moisture in the shaded lower canopy. The lower branches are also to the source of the spores that are coming from the chickweed plants.  The infection of the firs happens in the spring when rust spores travel from chickweed to fir tree needles at bud break.  With enough moisture those spores can germinate, penetrating the needles and later in the season  producing  spores on the needles that can only infect chickweed, continuing the cycle. Both mouseear and common chickweed are susceptible to this disease.  These weeds often grow unnoticed amongst grasses in Christmas tree fields.

Mouseear & common chickweed. (Click for expanded view.)

There are no fungicides registered to control this disease on fir trees.  Fortunately it can be managed by controlling the chickweed in the field with broadleaf herbicides.

For more information see this factsheet:


White Pine Weevil

July 8, 2013 · No Comments · Insect Pest

Dieback due to white pine weevil larva feeding.

Noticing a wilted leader on pines or spruces?  White pine weevil is likely the culprit. Although it’s almost officially summer when the symptoms are first noticed it all started back in the early spring when, on a warm day in March- April, the female weevil lays her tiny eggs a few inches below the terminal bud. Those eggs soon hatch and the young larvae start to consume the stem’s vascular tissue.    With the loss of this vascular pipework the tree’s terminal leader wilts and brown dieback soon becomes visible.

With the bark peeled back, a white pine weevil larva is visible inside spruce leader.

In late July and August adult weevils emerge through small holes they carved at the base of the dead terminal.  After the adult weevils emerge they enter leaf liter and are not seen until March of the following year.  If you prune out and destroy the affected leaders before the holes appear and the adults emerge (Late June to mid-July for most of New York) you can reduce numbers of adults that will lay next year’s eggs.

Exit holes of at base of area damaged by White Pine Weevils. Prune and destroy before these are visible.

A blue spruce disfigured due to a missing leader caused by White Pine Weevil damage.

White pine weevil is one of the earliest pests we treat for in the spring.  Knowing when to treat can be tricky.  Using growing degree days in the spring can be helpful to prevent damage.  

See the Insect Section of Pest Management Guide for Commercial Production and Maintenance of Trees and Shrubs for growing degree day target window for treatment  and other control information.  Scroll down to White Pine Weevil in this link:


Allies in the Trees

June 7, 2013 · No Comments · Beneficial Insects

Do you recognize this one? I saw this insect at a couple of tree farms during the last week of May and first week of June. This is an immature ladybug a.k.a. Ladybird beetle. The ladybug larvae, like the adult beetles they become, are voracious eaters of aphids and other insects.

Ladybug larva. Click on image for larger view.

ladybug pupa

The larva becomes a pupa before morphing into an adult beetle.

ladybug adults

An adult ladybug may consume 5000 insects in its lifespan. The ladybug on the right is on its way to a meal of balsam twig aphids.

ladybug eggs

This is a good sign. Bright yellow ladybug eggs hanging from a fir needle means more of these “eating machines” will be hatching soon.

There are many other beneficial creatures, which feed on pests in tree farms and often go unnoticed.  These include “good” mites, various predatory and parasitic insects, spiders and even birds.  By keeping pesticide applications to a minimum the populations of the beneficial partners are maintained and nature can do its good work without us even knowing it. 


Quince Rust on Junipers

May 21, 2013 · No Comments · Plant Disease

Another rust disease in the cedar rust group, quince rust is the most likely to cause serious dieback on junipers.

With this disease the bright orange “galls” are actually just slightly swollen lesions on the stems. Widespread lesions can lead to significant browning of the branch tips as pictured above. Spores which spread from these galls in the spring infect the alternate hosts of quince, hawthorn, crabapple or apple tree leaves. On hawthorn trees this disease causes causes symptoms on the leaves, white fringes on the fruit and swellings and distortion of the branch tips.

As with  similar rust diseases separating the juniper from the alternate host (the further apart the better) can help keep this disease in check.

For lists of resistant varieties and fungicides labeled for managing this disease refer to the Disease Section of  Cornell Guidelines for Commercial Production and Maintenance of Trees and Shrubs.


Hawthorn Rust

May 14, 2013 · No Comments · Plant Disease

Bright orange swellings can be seen at this time of year on some Eastern redcedars and other junipers.  After a rain those small, translucent-orange galls with gel-like projections appear.  These weird galls are caused by an intriguing fungus that needs two different host plants to live!

Hawthorn rust galls on Eastern redcedar.
Photo take in May, Onondaga County, NY.

Close up of galls. (Click for expanded view.)
Photo take in May, Monroe County, NY.

In the spring the orange masses expand after a rainfall and release  spores that can travel though the air and only infect the leaves of a hawthorn, apple tree or similar host (see below).  Then in the fall, from spots that formed on the hawthorn or apple leaves, spores are produced that can only infect a juniper/cedar.  The cycle continues in the spring when you can see new galls on the juniper/cedar.  Although a problem for apple growers this rust disease does not cause serious harm to the junipers.   There are other rusts that can cause problems with junipers such as quince rust.

In addition to the foliage of hawthorn and apples this disease can occasionally affect the leaves of affect crabapple, service berry or quince or pear.  However this disease does not affect any other evergreen tree species.  Only  redcedars and junipers can become infected.



Armillaria Root Rot (Shoestring Rot)

April 26, 2013 · No Comments · Plant Disease

Fraser fir killed by Armillaria

This disease is caused by several species of the fungus Armillaria.  It is also known as shoestring rot due to the dark wiry strands it produces.  These fungal “shoe strings” can spread the disease.  It most frequently attacks trees weakened by environmental stress or other factors.

Unfortunately the shoestrings are often confused with roots. One of the easiest ways to recognize the disease is the white layer of mycelium that can be found under the outer surface of the roots or just below the bark at the base of the tree.

This fungal disease will sometimes produce small groups tan colored mushrooms near the base of affected trees.  Although not present every year the mushrooms most often appear in the early fall following rainy weather.


White mycelial fan on trunk

Fungal “shoestrings” on rotting stump next to infected tree

Disease Management:

·      Keep tree vigor as high as possible to avoid tree stress

o   Avoid planting trees in droughty or poor planting sites. 

o   Water trees, if possible, during extended periods of drought.

·      If found remove and destroy stumps and roots of affected trees.

·      Plant new trees as far as practical away from where an affected tree was removed.

·      Avoid planting new trees in a recently cleared woodlot that had a problem with Armillaria.


Springtime Late Frost and Freeze Damage

May 24, 2012 · No Comments · Abiotic

2012 Brought Weather Extremes in the Spring

Lilac in full bloom weighed down by snow – April 2012

Coming off a record mild winter, we had temps in Upstate NY  that reached 80 F in mid-March, the mid- to upper 80’s F in mid-April and then a low in the mid-20’s at the end of April.  May was drier than normal for most in upstate NY and in some areas we were about inch or more below the normal rainfall in May.


What does all this mean for growing trees? 

Frost and freeze damage was common especially in the low lying areas of fields.  This year it was about early warmth rather than late frosts.

Concolor fir – terminal bud killed from low temps

Spruce- bud, center, killed from low temps

It seems that there are enough surviving buds on trees in many locations, so trees will able to compensate for the lost growing points and little differences will be noted when pruning this summer.

Turkish fir – buds killed due to low temps

For those managing certain pests like White Pine Weevil, which must be controlled early in the spring, growers needed to be ready extra early and it was very short window of opportunity to get treatments in place.

If possible, this year’s new transplants could benefit from irrigation


The drier weather, during needle expansion, may make it easier to stay on top of the fungal needlecast diseases of Douglas fir.  But the lack of normal rainfall  is also stressing the transplants that were set into the fields earlier this spring.