Sunday, August 25, 2013

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.

Sunday, August 11, 2013

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.

Sunday, August 4, 2013

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.