Mechanical Damage
Click for larger image Scars on tree trunk from use of a weed whip

Mechanical damage is a generalized term to describe damage to vegetation from using equipment and from weather related events. Damage to vegetation from equipment can be simple carelessness or incorrect use of the equipment. Some of the smaller gasoline or electric tools are relatively easy to use if the operator is familiar with them and careful in their use. A lapse in attention can cause damage both to the user and vegetation. Larger grading/trenching equipment is heavy and not only compresses the ground but easily damages root systems of trees and shrubs. Structural damage to trees and shrubs from weather events is not predictable. Ice, sleet, hail, and tornados can cause substantial harm with little warning.

Light equipment

Damage to trees and shrubs from hand operated equipment happens frequently. These tools include weed whips, lawn mowers, tree trimmers, chain saws, hedge trimmers and the like. Much of this damage is preventable and associated with lack of attention to the task at hand. Unfortunately the injuries to trees and shrubs are often repeated with cumulative damage to vegetation. Typical injuries to trees and shrubs include gouges and cuts through the bark into the cambium, where cells actively divide. These injuries are often close to the ground and easily invaded by insects and disease causing agents. Younger vegetation is more susceptible, and extensive damage will kill the shrub or tree. Also, tools are frequently used without adequate safety precautions—leather gloves, eye protection, ear protection, or with loose clothing that can be caught in the equipment.

Heavy equipment and compaction

 Heavy equipment use is often associated with digging trenches and ditches. The digging not only disturbs root systems, but also the soil removed may damage nearby plants when it is placed near or on top of other plants. There is double damage from equipment use, with compression of the soil by the weight of the machine and piling of tons of excavated soil near or on other vegetation. Some of this can be avoided by careful planning of the excavation and through the use of heavy sheets of wood or plastic that spread the weigh of the equipment.

Damage from excavations

Excavating for sewer, water and gas lines, installing sprinkler systems, underground electric lines and drains all require removal of soil. In some instances multiple installation sites are involved requiring large areas where the soil is disturbed. Not only is the ground dug up and vegetation potentially damaged, but refilling the holes often leaves clay and poor quality soil as topsoil. Obviously this new “topsoil” is a poor replacement for the original. Often soil in these areas will have to be amended before they can again be used for vegetation.

Weather related damage

Weather related damage to trees and shrubs can be substantial. The amount of ice, sleet and hail determine the severity of the damage. Ice and sleet weigh down branches and can cause breaking of limbs or splitting of the trunk itself. Some trees and shrubs are more susceptible than others, and age and health of the plant are determining factors. Wind, storms and tornados vary as to the amount of damage they can cause. Trees that have leafed out have a greater resistance to the wind and are more easily damaged than deciduous trees in late fall or winter. Tornados in any season will cause damage. Floods can be relatively brief, and the amount of harm is dependent on water level and length of time the trees or shrubs are covered with water.

Improper tree care

Many practices associated with improper tree care result in mechanical damage to trees. Crossed limbs can rub and cause damage; synthetic twine, wires, or cages can girdle roots stems and branches.

Integrated Pest Management Strategies

1. Prevention. Ideally damage from mechanical means should be prevented. Learn what can cause damage to your trees and implement safeguards that can prevent their occurrence. Keeping grass and weeds from growing at the base of a tree can help prevent damage from weed whips and lawnmowers. Avoid using heavy equipment around trees especially when the soil is wet and subject to compaction. Prevent or limit damage to a tree’s root system. Generally, the closer the damage occurs to the trunk of the tree the more risk of serious damage. Explore the possibility of tunneling below the top roots (18-24 inches deep) if pipes or wires need to run close to an existing tree as opposed to cutting through the roots.

2. Clean up the damaged site well. If branches are broken or damage occurs to the bark or trunk of a tree, prune the broken branch back to a side branch or make clean edges on the bark on the trunk. Ragged edges and loose bark can provide homes for insects and encourage disease. Clean up the wound but do not apply pruning paint or a wound dressing. Leave the cleaned wound exposed to the air so it can dry and heal over naturally.

3. Aerate the soil. If heavy equipment has compacted the soil, core-aerate the area to help provide needed oxygen in the soil.

Organic Strategies

All of the recommended IPM strategies are strictly organic approaches.

More images:

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Injury from tree climbing spikes
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Woody plants try to recover from damage by callousing over the injury; note, the thickened bark (callous tissue) at the edges of the crack. The cause of this injury is unknown.
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Strings tied around the ends of the branches on a row of arborvitae (Thuja) cut off the flow of sugars from the growing tips down to the roots, resulting in enlarged branch tips that eventually died.
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Enlargement of branch tips on arborvitae (Thuja) caused by a string blocking the flow of sugars from the growing tips down to the roots.
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Branch tip on arborvitae (Thuja) girdled by a string. Branch tips eventually died.
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Branch tip on arborvitae (Thuja) gridled by a string.
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Cut away of stem on an arborvitae (Thuja) girdled by a string. Enlarged area is branch tip.
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Girdling to small tree from a weed whip
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Limb torn off by a backhoe
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Limb torn off by a backhoe
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The roots of this oak (Quercus) were cut on one side and damaged on the other from soil compaction due to the soil piled up in the root zone.
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Mechanical damage to this pear tree (Pyrus) caused tattered leaves and flagging in the canopy.
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Tattered leaves on a maple caused by mechanical damage
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Distorted trunk and stunting of ash (Fraxinus) due to mechanical damage
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Callus tissue forming over pruning scar
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Physical injury to trees caused by repeatedly hitting the trunk with a lawn mower can eventually lead to dieback and tree death.
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Placing heavy items in the root zone of a tree or shrub --here a maple (Acer) -- compacts the soil and can lead to root injury, decline and even death of the entire tree.
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Heavy equipment compacts the soil. Placed in the root zone of a tree, it can injure tree roots, leading to decline and even death of the tree.
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When the foundation was dug for the house on the left the roots of this tree were cut, making it vulnerable to toppling from the weight of an ice storm.
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Crossing or rubbing branches should be removed because they injure plant tissue and can provide and entry for insects and diseases.
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Plant roots cannot thrive in compacted soil. Without roots, plants, such as, lawn grass, will die. Note the tire track indicating the cause of the compaction.
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Splitting caused by narrow angle crotches and included bark on Bradford pear (Pyrus)
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Splitting caused by narrow angle crotches and included bark on Bradford pear (Pyrus)


Pests and Problems

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