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NUMBER 1219 January 26, 2010


2010 IPM Training – March 3
By Patricia Lucas

The 2010 IPM Training School will be held on Wednesday, March 3, at the University of Kentucky Research and Education Center in Princeton. Registration will open at 8:30 AM with the meeting starting at 9:00 AM and ending at 3:30 PM.

Topics to be covered include corn nematodes, build up and draw down of soil potassium, grid sampling in support of lime, P and K application, common Kentucky endangered species and agriculture, controlling volunteer corn in soybeans and potential insect problems due to the presence of volunteer corn.

The program is free of charge and lunch will be provided. To guarantee a lunch, call MaryAnn Kelley at (270) 365-7541 extension 216 or e-mail before March 1.

The program has applied for 5.5 CEU’s for certified crop advisors (1.5-Pest Management, 1.5- Crop Management, 1- Nutrient Management and 1.5 Soil and Water Management) and for pesticide applicators hours in categories 1A, 10 and 12.


By John Hartman
  Figure 1. Mushrooms of the Armillaria fungus, cause of oak root rot, growing at the base of an infected tree.   Figure 2. Hypoxylon canker disease of oak is seen as tan to dark brown patches of fungal stroma on the infected limb.

Why trees decline in the landscape is an inquiry received regularly in the field and the plant disease diagnostic laboratory. Declining trees often are infected by an opportunistic fungal pathogen such as Armillaria (Figure 1) or Camillea a.k.a. Hypoxylon (Figure 2), but these organisms may not have started the decline. Construction activities can often be found as the initial cause of the problem, often many years before symptoms of decline are evident.

Tree owners are often very concerned about the potential loss of their trees for a variety of reasons. Trees add to property values by improving aesthetics. Trees have ecological benefits by reducing carbon dioxide production through lowering fuel consumption for heating and cooling, sequestering carbon dioxide as carbon, and by providing wildlife food and shelter. In some locations, trees have been shown to reduce crime rates. Trees may also have emotional value. I have seen tree owners place signs along the street indicating their concern over loss of trees due to utility construction, for example. So how can construction activity affect tree health?

Figure 3. Backhoes digging utility trenches rip tree roots apart, exposing injured roots to infection by decay fungi.   Figure 4. Heavy construction equipment compacts soil in the tree root zone.  

Construction harms existing trees by cutting roots. Whether it is a building foundation, utility trench, or curb installation, nearby construction severs tree roots. Cutting most of the roots on one side of the tree removes needed anchorage and could cause the tree to topple in a storm. Even construction so minor as sidewalk repair can cause major problems for the tree. Backhoes, often used to excavate utility trenches, rip interfering tree roots apart leaving exposed, wounded roots (Figure 3). In some cases, while being
mindful of the trees, utility trenches are run down the middle of the street, but the property owner chooses to locate lateral lines to the home too close to the roots of the street-side tree.

Construction harms existing trees by compacting soils. Good soil should contain 50% pore space for aeration and moisture retention. Tree roots need oxygen to function. Heavy equipment compacts soil, reducing oxygen and inhibiting root penetration (Figure 4). Even piling soil and construction debris or parking workers’ vehicles over the root zone squeezes air out of pore spaces. The effect is worsened if the soil is wet.

Construction harms existing trees by burying roots and trunk. Roots normally grow in the top foot of soil. Piling soil or increasing the grade smothers the roots (Figure 5). It takes only a few inches of added soil to kill a sensitive tree.

Construction harms existing trees by causing wounds. Basal wounds are especially harmful because decay can spread to the roots leading to tree instability (Figures 6 and 7). Small trunk injuries may close easily; larger wounds may lead to internal decay. Split and broken branches resulting from heavy equipment operation will cause decay and hazard problems later.

  Figure 5. Soil and debris piled on the construction site can smother roots.
Figure 6. Basal injury to tree following construction activity.    
    Figure 7. The fungus Ganoderma, cause of root and butt rot, entered the tree through injured roots of trunk following construction and is fruiting at the base of the tree.  

Construction harms existing trees by exposing trees to the elements. Trees formerly growing in woods and protecting each other from wind and sun are exposed after construction. Thinning out groups of trees to showcase individual trees on a wooded lot can lead to tree decline.

In most cases, homeowners, builders, and developers are wary of causing too much injury to exposed parts of trees such as the trunk, limbs, and branches. However, tree roots seem to be the most vulnerable to construction activity because their location is poorly understood and they are out of sight. Most tree roots grow in the upper 6 – 12 inches of soil, so even a shallow trench will cause great harm. In addition, if unobstructed, tree roots extend out in all directions the height of the tree or more. This becomes a large area to protect from cutting, compaction, and grade changes. Where construction is being considered on wooded lots or near any existing trees, builders and homeowners are urged to consult with a certified arborist during the design of the building before any construction is begun.


Information and recommendations in Kentucky Pest News are have been written for audiences in Kentucky. Readers outside of Kentucky should be aware that situations and regulations in Kentucky may differ from those in their particular location, and should consult their local Cooperative Extension Service for guidance.

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