The Band, a spray alternative.

When controlling pests on trees and shrubs we often think of spraying some kind of chemical product, and while this is often our only course of action, for some pests there are alternatives.  Many pests can be physically removed.  Webworms and tent caterpillar nests can be pruned out or destroyed.  White peach/prunicolia scale can be scrubbed off the stems of small cherry laurels and lilacs.

Another non-chemical method for preventing pest injury to trees is creating a physical barrier.  This is most effective against certain species of lepidoptera that climb from the ground in to the canopies of trees to feed or lay eggs.  In the Charlotte, NC metro area there's an unprecedentedly large population of fall cankerworms (Alsophila pometaria).  There are many theories as to why cankerworm numbers are so large, but no doubt part of the problem lies within the overwhelming number of mature willow oaks (Quecus phellos) lining streets and gracing private yards.  

Cankerworm adults emerge from the ground after the 1st series of cold nights (at or below freezing) in the late fall/early winter.  The adult female cankerworm doesn't have wings, and is forced to climb up the trunk into the canopy of a tree to mate and lay eggs.  Each female can lay  between 100-200 eggs.  In spring, just as leaves are approaching full expansion, the little inching cankerworms emerge from their eggs and feed on the tender young foliage.

These cankerworms are present in such damaging numbers that the city of Charlotte, and most of her residents, habitually affix bands covered or lined with sticky stuff to trees throughout the fall.  This way cankerworms are controlled safely and economically.

Heartwood Tree Service Arborist affixing 'Bug Barrier' to the trunk of a willow oak.

Is it over reacting?

Trees respond to damage or decay by forming reaction wood.  The placement and extent of reaction wood can be telling of where and how long the tree has been affected by decay.  When we think about a tree responding to decay organisms,  most often our first thought is the compartmentalization of decay in trees (CODIT) model.  However, the CODIT model is based upon a tree's reaction to damage to the bark and cambium.  When decay enters from the tree's structural root system, or perhaps an old tap root that has died off, trees react a little differently since the decay organism is growing in duramen (heartwood) tissue, which is effectively dead structural tissue.

The root flare of the willow oak pictured below has been quite disfigured by years of attempting to out grow Inonotus dryadeus and Ganoderma lucidum.  When sampled with an IML-Resistograph, what appears to be a substantial amount of wood reveals areas and pockets of substantial decay.

That's going to be trouble...

When assessing a tree's risk of failure we must sometimes look for the finer signs and symptoms that may indicate a tree's potential to fail.  The convenience of giant decay conks, broken roots, and huge decayed cavities may not always be evident on a tree that presents a high risk of failure.

Let's look at some pictures of a tree that from a distance may seem fine, but upon closer inspection proved to be cause for alarm.

Notice the soil heaving on the tension side of the lean.

Saw dust or frass present on several areas around on the lower trunk.  When sounded with a hammer decay was detected.

Small armillaria fruiting bodies protruding from the root flare of the tree on the tension side of the lean.  Armillaria root rot is a serious structural root decaying fungus which results in a white rot.

From a distance this willow oak has a perfectly green and balanced canopy, and is in a beautifully maintained yard.  Upon closer inspection the tree described above displays some serious evidence of strength loss.  Further proof that when walking a property, we can take nothing for granted.

I'm fallin'

When discussing tree risk assessments we talk about looking for signs a tree is likely to fail.  The following pictures are of a white oak that some may argue is in the process of failure.  Let's take a look....

As we approach the tree, notice first the lean. What this picture doesn't show is the residence within 50ft of the tree's base.

Soil heaving, especially on the side of the tree opposite the lean, is pronounced.

Here we can see where large roots are separating from the soil.

Another image of large roots separating from the soil, and some resulting voids in the soil.

After discussing these issues with the client I discovered that 5 years ago this white oak was on the edge of a wooded area that had been cleared to make room for a new home lot.  This tree had spent most of its existence to this point with mature neighboring trees protecting it from wind and storm events on the side opposite of where it is now leaning.

By altering this tree's environment, a tree that may have lasted for years to come was turned in to a tree that is now at an extremely high risk for failure.

Don't be STUBborn

For decades we've known when pruning the final cut should be at, or just outside, the branch collar.  When trees shed branches naturally it's at this point. This is where the tree has the easiest time compartmentalizing and growing over the wound.

Now, it seems there's been some debate over the past few years about what to do when pruning larger branches back to parent stems on mature trees.  Some seasoned arborists have insisted that leaving a stub is prudent when dealing with large branches.  The idea is that by leaving a stub, decay will be slowed when moving into the stem.  

What needs to be considered though, is in a short period of time the vascular system around this stub is going to die.  This means any physiological process the tree has to fend off decay will cease, creating a corridor for decay to enter the parent stem through both heartwood rots and sapwood rots.

Below is a picture of a willow oak damaged in a storm 3 or 4 years ago.  During the storm a large branch broke out leaving a substantial stub.  In that time I've driven past this tree almost every day.  A few weeks ago I noticed bark separating from the underside of the damaged limb.  When I got out to look, it was obvious that sapwood decay had moved from the dead stub into the parent branch.  Had a proper cut been made the tree would have had a better chance of reacting to the damage.  Sure, decay still may have moved in to the stem, but the tree would have been putting on reaction wood to close the wound and reinforce the structural wood around the damage.

The red arrow shows where decay has moved from the damaged stub into the parent branch.  You can also see wound wood forming around the decay.  This has become a large area to heal over vs. if a proper cut was made at the branch collar.

It's Phytoplasmatic

Phytoplasma are specialized bacteria-like organisms that are obligate parasites of phloem tissue, and they can do strange things to plants.  Phytoplasma can cause leaf yellowing/variegation, twig distortion, witches brooms, etc.  They are spread by insects, like leaf hoppers, from infected plants to new hosts. 

In most instances infection by phytoplasma is not big deal, but in the case of a few diseases, namely; elm yellows, ash yellows, lilac witch’s broom, and grapevine yellows it can be deadly.  The best control method of phytoplasma is the removal, and offsite disposal of affected plant material.  Insecticide treatments to control the vectors may be helpful as well.

Diagnoses of phytoplasma can be difficult.  Viruses, bacteria, and fungal infections can mimic phytoplasma symptoms.  The picture below is a willow oak branch displaying some weird symptoms.  What’s causing it?  Phytoplasma?  Sure.

'Crispy black stuff'

Wood decay fungi come in many shapes and sizes.  Their fruiting bodies are generally pretty easy to identify.  Mushrooms and conks along the base of a tree or attached to the trunk can be eye catching.  One commonly over looked and miss identified structural root/basal decay fungi is Brittle Cinder Fungus (Kretzchmaria deusta  formerly Ustulina deusta).  Brittle Cinder causes a soft rot that breaks down cellulose and hemi-cellulose followed by lignin.  This creates a decay that leaves wood feeling brittle.  Early stages of this decay can be hard to detect with a traditional 1/8th-inch bit and drill.

Perhaps the hardest part of identifying this decay fungi is simply noticing it.  Brittle Cinder fruiting bodies first appear as grey-white masses growing only slightly raised from the bark of the tree.  At first sight, they may be mistaken for dead lichens.  As the fruiting bodies mature, they become black and appear as burned bark.  Deusta means 'burned up.'  Unlike most common wood decay fungi, Brittle Cinder is an Ascomycota versus a Basidiomycota.

Brittle Cinder affects a vast array of tree species,including; beech, oak, maple, and linden.  Infection usually occurs through wounds in the bark.  Brittle Cinder can result in significant strength loss, so careful consideration should be taken if this fungus is located on a tree.

Here, Brittle Cinder is growing on the root flare of a red maple.  There is only 1.5-inches to 0-inches of sound wood around the affected area.