Arbor News - 2009
Previous Arbor News Publications
Notes from the Arborist
By Brian Cassity
Emerald Ash borer continues to be the greatest immediate threat to our tree cover in Wisconsin. Unfortunately, in wooded natural
areas no effective control of EAB is yet possible. As private home and property owners however, control options are getting better.
Initially, it was decided that once this pest got started in a tree, there was no hope of saving it. Now, research indicates that we can
save trees with up to 40% crown dieback with certain chemicals and techniques. The soil injection process we have been using for the past
several years is still the most favorable as a preventative. This is especially true after trees receive treatment for several years and
residual builds in the trees vascular system. Other available processes involve sprays that typically get on non target areas or direct
trunk injections that create a wound on the tree. If trees do get infested, we have the very latest information, products, equipment and
experience to handle those cases as well.
Reconnecting Young Children with Nature
By Susan Wirth
Children must develop an emotional connection with nature at an early age if we hope to have future generations of tree planters,
arborists, and environmental stewards. Yesterday’s children typically spent hours playing outdoors climbing trees, jumping into piles
of leaves, collecting nature’s treasures. These experiences helped shape their views of the world. Now, indoor media capture most of a
child’s time, while fascinating adventures outside remain unexplored. Today, even when children do go outside, their outdoor play spaces
often consist solely of plastic play structures on asphalt. A critical aspect of the present-day crisis in education is that children
have become separated from daily experiences of the natural world.
Research with groups of children from preschoolers to children age nine, found that the attitudes today’s children expressed toward
various aspects of the natural environment (rain, wildflowers, trees, birds) included more expressions of fear and dislike than appreciation,
care, or enjoyment. An early emotional connection with nature underpins a love for trees and the environment as an adult. Such emotional
interactions cannot be reproduced indoors, on a computer, or in a video. Research shows that children benefit greatly from connecting with
nature. These benefits include -
Firewood-The Unwitting Emerald Ash Borer Vector
• Increased math and science skills
• Strengthened powers of observation and imagination
• Enhanced motor skills, including balance, coordination, and agility
• More active outdoor play, resulting in decrease of childhood obesity and improved health
• Improved ability to concentrate, even among children with behavioral challenges such as A.D.D.
• Increased sense of wonder that inspires lifelong learning.
Moreover, these benefits are shown to have a lasting impact, especially when positive outdoor experiences come at an early age. And, as
a result of their children’s increased interest, families report engaging in more outdoor activities, including outings to natural areas.
There’s no such thing as “free” firewood anymore!
It has become painfully obvious to many of our communities over the last several decades for the need to change our behavior-professionally
and as consumers-in the production, distribution and movement of firewood. This is again being brought to our attention in the wake of the
emerald ash borer and other invasive infestations. How often have we seen piles of ‘free’ firewood left curbside for the taking, with no thought
to the potential spread of diseases, borers-adult, pupae or egg masses-or other invasives by neighborhood “bargain hunters’ as they pull up
alongside with their pickups or trailers? How do we define ‘firewood’ other than the standard measure of cord volume? What incentives are needed
for campgrounds and their firewood ‘destinations’ to supply sufficient ‘certified, pest free’ firewood for their users? How can regulations,
education, outreach and value-added economic programs band together to minimize the threat of vector movement through firewood distribution?
Chlorosis? What’s that?
By Susan Tangen Certified Arborist WI0684A
Your tree has been diagnosed with chlorosis, but you wonder, what does this mean? Chlorosis is caused by the trees inability to manufacture chlorophyll,
the green pigment in leaves. The importance of chlorophyll is sunlight absorption, which is the first process in photosynthesis; the function of
photosynthesis is sugar production which provides food for the tree. Therefore, trees that suffer from chlorosis produce less food which can result
in weaker, less durable trees that rarely make it to maturity. Because there is a lack of chlorophyll in the leaves, chlorosis is easily diagnosed
by looking at the leaf color, which may appear pale green, yellow or whitish. The causes of chlorosis are complex and not fully understood; however,
as a general rule of thumb it is caused by a lack of a mineral or a combination of minerals which the tree needs to produce chlorophyll. There are
several factors that can affect the availability of minerals in the tree. However, the two most significant factors are high pH soils, which are
very common in southeast Wisconsin, and poor root health. Other factors may be over irrigation, repeated drought, root severing, deicing salt, and
root rot/diseases. Depending on the severity and cause of the chlorosis, these are several treatment options including trunk injection, soil
fertilization, lowering soil pH, and improving root health. Remember, the goal is to help the tree increase chlorophyll production. So, if the leaves
on your tree are pale green, yellow, or whitish, do not delay, your tree is telling you it may be chlorotic.
Recognizing Hazardous Defects in Trees
1. Dead Wood
A ‘hazard tree’ is a tree with structural defects likely to cause failure of all or part of the tree, which could strike
a ‘target’-a vehicle building, or a place where people gather such as a park bench, picnic table, street, or backyard.
Hazardous defects are visible signs that the tree is failing. This article points out five main types of defects: dead wood,
cracks, weak branch unions, decay, and cankers.
Dead wood is not negotiable. If a dead tree or large dead branch is hazardous, you must remove it immediately! Dead trees
and branches are unpredictable and can break and fall at any time. Dead wood is often dry and brittle and cannot bend in the
wind like a living tree or branch. Dead branches and tree tops that are already broken off (‘hangers’ or ‘widow makers’) are
2. Weak Branch Unions
Take immediate action if…
• A broken branch or top is lodged in a tree
• A tree is dead
• A branch is dead and sufficient size to cause injury (this will vary with height and size of branch)
Weak branch unions are places where branches are not strongly attached to the tree. A weak union occurs when two or
more similarly-sized, usually upright branches grow so closely together that bark grows between the branches, inside the union.
This ingrown bark does not have the structural strength of wood, and the union is much weaker than on e that does not have
included bark. The included bark might also act as a wedge and force the branch union to split apart. Trees with a tendency y to
form upright branches, such as elm and maple, often produce weak branch unions. These weak unions also form after a tree or branch
is tipped or topped-for example, when the main stem or a large branch is cut a right angle to the direction of growth, leaving a
large branch stub. The stub generally decays, providing very poor support for new branches (‘epicormic’ branches) that usually
develop along the cut branch.
Take action if…
• A weak branch union occurs on the main stem
• A weak branch union is cracked
• A weak branch union is associated with a crack, cavity, or other defect
A crack is a deep split through the bark, extending into the wood of the tree. Cracks are extremely dangerous because they indicate
that the tree is already failing.
Take action if…
• A crack extends deeply into, or completely through, the stem
• Two or more cracks occur in the same general area of the stem
• A crack is in contact with another defect
• A branch of sufficient size to cause injury is cracked.
Decaying trees can be prone to failure, but the presence of decay, by itself, does not indicate that the tree is hazardous. Advanced
decay-wood that is soft, punky, or crumbly, or a cavity where the wood is missing-can created a serious hazard. Evidence of fungal
activity such as mushrooms, conks, and brackets growing on root flares, stems, or branches indicated advance decay.
A tree usually decays from the inside out, eventually forming a cavity, but sound wood is also added to the outside of the tree as
it grows. Trees with sound outer wood shells may be relatively safe, but this depends upon the ratio of sound to decayed wood, and
other defects that might be present.
Take action if…
• Advanced decay is associated with cracks, weak branch unions, or other defects
• A branch of sufficient size to cause injury is decayed
• The thickness of sound wood is less than 1’ for every 6’ of diameter at any point of the stem
A canker is a localized area on the stem or branch of a tree where the bark I sunken or missing. Cankers are caused by wounding or disease.
The presence of a canker increases the chance of the stem breaking near the canker. A tree with a canker that encompasses more than half of
the tree’s circumference may be hazardous even if exposed wood appears sound.
Take action if…
• A canker or multiple cankers affect more than half of the tree’s circumference
• A canker is physically connected to a crack, weak branch union, a cavity, or other defect
Does Pruning Reduce The Risk of Tree Failure?
Effects of Wind Speed and Tree Shape on Drag
Engineers and physicists call the force of the wind on a tree “drag”, and the equation they use to predict drag shows
that it is related to several dactors, the most important of which are the shape and area of an object and the wind speed.
We see evidence of why shape is important in the design of new cars, which have a streamlined profile. If two cars have
the same area, but one has a more streamlined profile, it will experience less drag. Because its’ usually not practical
to change the wind speed around tress, arborists are left to change the size and/or shape of a tree to reduce drag. Pruning
obviously reduces the canopy area of a tree and, intuitively we expect that drag should be reduced. Pruning also changes
tree shape, which affects whether wind can flow freely through or around the canopy and the height at which pressure is
centered. Which is the height at which the drag can be assumed to act. In general, if the canopy is more porous, it’s easier
for wind to flow through it. Leverage is important because the same force that acts on a longer lever creates greater torque
or bending than a force that acts on a shorter lever. Of the common pruning types, reduction pruning reduces the height of
the center pf pressure because the canopy is shortened. On the other hand, raising increases the height of the center of
pressure because only the lower branches are removed. Thinning doesn’t really change the center of pressure height. Of the
three common pruning types (raising, reducing, and thinning), reduction pruning seems to do a better job at reducing drag
and bending on trees when the weight of foliage and twigs removed has been account for. Obviously, if you prune out more
foliage and twigs, you’ll reduce more drag, but over-pruning adversely affects tree health. Raising appears to be the least
effective type of pruning to reduce drag and bending, because raising increases the height of the center of pressure and
increases leverage. Leaves experience much more drag than twigs and branches. Consequently, pruning types that remove
proportionally more foliage than branches should be more effective at reducing drag.
Wisconsin Tree ID on Your iPod
The University of Wisconsin’s Department of Botany has developed a new tree and woody plant identification tool. It is
a free software program downloadable to your iPod for a portable, easy-to-use guide to all native trees and shrubs of the
state, as well as common exotic species. It uses a dichotomous key with color images that can be viewed on your iPod screen.
It is browsable by common or scientific name and also includes a glossary.
A Bit of Tree Humor
Previous Arbor News Publications
Last October my wife bought a magnolia tree from the local nursery, but after only a few weeks the leaves shriveled. It appeared
to be on it’s last legs. So my wife took some leaf samples and marched into the nursery to demand an explanation. “I know exactly
what’s wrong with your magnolia,” said the manager. “Good”, said my wife. “What’s it suffering from? “Autumn”, he replied.
This newsletter has adapted articles from the publications of the following organizations in addition to our original pictures and stories.