Posts Tagged ‘tree damage’

Mild spring temperatures and abundant moisture have created favorable conditions for Fire Blight.  Flowering Pears throughout North Central Texas are symptomatic, making this the largest outbreak in more than ten years.  Caused by the bacterium, Erwinia amylovora, Fire Blight is a disease that primarily affects Pears, Apples, and closely related plants.  While Bradford and Aristocrat Flowering Pears are known to be resistant to Fire Blight, both named varieties have not been able to escape this year’s outbreak.

Fire Blight is easily recognized by the scorched appearance of leaves, fruit, and stems

Fire Blight is easily recognized.  It derives its name from the scorched appearance of affected foliage, fruit, and stems.  Infected tissue rapidly turns black and leaves and fruit droop from their attachment to stems.  While there may be some leaf drop, most of the damaged leaves remain in the tree canopy.

When Fire Blight infection sites are spread throughout the canopy, disease management by pruning is impractical

Pollinating insects commonly spread Fire Blight from tree to tree, as they travel from flower to flower.  While there is no “cure” for Fire Blight, it can be successfully managed with carefully timed spray applications of bactericides.  Those spray applications will be necessary next spring, just as the flower buds begin to open.  Fight Blight can also be managed by removing infected twigs and branches.  However, pruning is only practical when infections are isolated.  This year’s outbreak has affected most of the canopies of Flowering Pears and much of the interior foliage, making the pruning of infected tissue unrealistic.

Fire Blight symptoms first appeared in North Central Texas during the last week of March and became wide spread in less than two weeks.  If your Flowering Pears are showing symptoms of Fire Blight and need to be addressed, contact the Arborilogical Services office by calling at 866-55-ARBOR, or complete a service request.

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Southern Magnolia showing heat damage on an irrigated site.

Given the current drought and associated water restrictions, important questions arise:  How do drought and heat affect plants?  How do you water and care for plants during an extended drought and the resulting water restrictions?  Before we can discuss watering plants, it is important to look at how they are affected by heat and drought.

Since tree roots in an urban landscape are intertwined with the roots of other nearby plants, a discussion about watering and care should include all the elements of the landscape as an integral ecosystem.  For the sake of brevity, let’s consider trees, shrubs, groundcovers, and turf to be covered by one term:  “plants”.

How does drought affect plants?

• On non-irrigated sites, drought, or the lack of rainfall, causes the loss of smaller feeder roots in the upper levels of the soil as moisture evaporates.  If drought conditions continue, roots at deeper soil levels are lost.  As soils lose more moisture to evaporation at the surface, they shrink by volume–which causes heaving and cracking.  Shrinking soils can cause physical injury to the root system of all plants.
  
  

  Silver Maple showing heat damage on an irrigated site.

• Smaller plants can be affected immediately as the top few inches of soil become dry.  It can take years for the full effects of drought to be apparent in larger plants.  Leaves of affected plants turn brown beginning at the edges.  As the browning moves toward the center of the leaves, the plant expresses a scorched look.  In some cases, primarily in large shrubs and trees, there is not a gradual burning of foliage, but rather a sudden onset of browning on all the leaves.  Trees that may appear healthy may turn brown very quickly many years after a drought.  In Colorado, Aspens, Populus tremuloides, are currently dying in great numbers.  Their loss is attributed to the drought from 2000 to 2004.
• If a disease, insects, or cultural conditions are an existing problem before the drought occurs, plants are more likely to be affected to a greater degree.

How does heat affect plants?

• On both irrigated and non-irrigated sites, extended periods of heat, slows the biological function of plants.  The effect occurs when daytime temperatures are over 95 degrees, regardless of the amount of moisture in the soil.
  
  

  Red Oak showing heat and drought stress on a non-irrigated site.

• Extreme soil temperatures also slow biological function.  In 2011, there were a record number of days with nighttime temperatures never dropping below 85 degrees.  No nights over 85 degrees were recorded during the last heat wave of 1980.  The loss of biological function is why plants, even on irrigated sites, were negatively affected in 2011.  Watering does not shield plants from heat damage.
• Some plant species are more prone to heat damage than others are.  For example, silver maple, Acer saccharinum, is not heat tolerant; while post oak, Quercus stellata, is unaffected.
• Increased air temperatures add to air pollution, affecting plant health.  Studies show that tree health is affected by air pollution.  I suspect that the same is true for all plants.

Unfortunately, the recent extended period of heat and the drought on non-irrigated sites creates the opportunity for insects and pathogens to wreak havoc on our plants for years to come.  Since trees have an energy reserve, they can sustain some damage from insects or pathogens.  Either they overcome the damage over time or they go belly-up.

Post Oak showing no signs of heat or drought stress.

The loss of trees around the state will have a direct impact on us in many ways.  The loss of shade increases energy costs.  The increased urban heat island effect diminishes our air quality.  Neighborhoods will also lose a part of their quality of life, and the erosion of precious topsoil occurs with the loss of foliage.

On the bright side, we have a great opportunity to replace stressed trees with more drought and heat resistant plants, which minimizes the negative impacts to our environment.  Heat and drought tolerant plants reduce water use and maintenance expenses.  They are a much better long-term investment.     

The best defense you have against drought and heat damage is an education that begins with recognizing the effects to your plants. 

Continue to  “Heat, Drought and Trees, Part II”

continued from Heat, Drought and Trees, Part I 

Even our native Mexican Plum tree is not immune to the effects of heat and drought stress.

Last month’s article touched on heat damage but the subject was not covered in detail.  As with the previous article, let’s consider all trees, shrubs, groundcovers, and turf to be covered by one term:  “plants”.

Regardless of the moisture levels in the soil, extended daytime periods of 95 degrees and above slow the biological functions of plants.  This slowing phenomenon, which protects plants by reducing water loss through transpiration, is known as “self induced dormancy”.  Transpiration uses water, absorbed by the roots and transported to the upper parts of the plant, to be released into the air.  This evaporative cooling is much like the piping that emits a mist to cool the air during the State Fair.

Unfortunately, this slowing of biological function also reduces the amount of plant food (sugars, carbohydrates, and others) produced and stored by the plant.  Although fertilizers are often promoted as “plant food”, they are actually elements that are absorbed by the roots and transferred to the foliage.  The foliage, with help from the sun, produces a plant’s actual food through photosynthesis.  The resulting food is stored in the plant’s tissues.  Extended periods of heat reduce the amount of time a plant can produce and store its food.  Given our Texas weather, even a Mexican Plum can be affected.

Reducing the effects of heat

Although some of our native plants were negatively affected by the extended period of heat in 2011, native and adapted plants are best suited to survive and function quite well.  Heat tolerant landscapes contain mostly native plants that are grouped in a natural setting or environment appropriate for the plant.  Including other native companion plants as part of a planting group helps to create (or restore) a natural ecological balance.  Any plant properly placed in a healthy and balanced ecological system will better survive anything that nature can whip up.  When we isolate plants from their normal companions or when the ecology is not in balance, it is much more difficult to keep them healthy.  Grouping species typically found growing together in nature, provides a greater level of protection from heat as well as other forces of nature.

Which species of plants may be native or adaptable to an area is often debated.  However, the late plantsman, Benny J. Simpson, researched various tree species from West and South Texas that are adaptable and heat/drought tolerant.  He was a true pioneer in native plant knowledge and a research scientist at the Texas AgriLife Research and Extension Center at Dallas.  The trees he planted in test plots off Coit Road, in Far North Dallas, were only watered for the first year or two–purposely.  His research groves are open to the public and still exist today without irrigation as an example of adaptable species that can tolerate both heat and drought.  Although many of these trees are not currently available in retail nurseries, they could be if more folks ask for them in the future, wink…wink. (http://aggie-horticulture.tamu.edu/ornamentals/natives/about.html )

If a smaller plant in your yard is not heat tolerant, covering it with a shade cloth or similar material may help.  Misters that emit water vapor around smaller plants during the heat of the day can help reduce heat damage.  Plants near a white or light colored structure or a glass wall may receive more reflected sunlight, adding to the potential for heat damage.  Also, plants in areas affected by the Urban Heat Island Effect must also be able to withstand increased surrounding temperatures (www.epa.gov/heatisland/).

If it can`t stand the heat, it may not belong in our Texas kitchen. 

Although most Texans think of drought and cold as the top enemies of trees, snow, ice and wind can create additional stress that leads to major breakage or toppling, a North Texas arborist told members of the Wood County Master Gardeners in a monthly meeting Thursday, Feb. 17, in Quitman. In the wake of recent heavy snowfalls in North Texas, arborist Steve Houser, who serves as chairman of the Urban Forest Advisory Committee for the city of Dallas, spoke about how to protect and repair damaged trees. “The best way to avoid damage is to understand the tree,” Houser told the group. Trees that, when they begin to branch, are joined in a U shape are stronger trees and more likely to weather the storms, he said. But those with tight V shapes are more likely to break. These are trees that may need a cable and bolt system to keep the branches from splitting. Equipment needed for the cabling is available at an arborist supply store, he said.Because fruit-bearing trees build up weight on the ends of the limbs, they are also vulnerable to breakage, although proper trimming can help, he said. Trim some of the smaller limbs at the end to relieve the weight, while making sure you leave a natural look, he said. But never take more than 20 to 30 percent off a tree because it will interfere with its food-making processes, he warned. Houser said last year he saw lots of damaged trees because of the ice and snow. When snow builds up especially on smaller plants, stand away from the plant and use a cane pole to gently knock off the snow, he said.The root system is also a very important to supporting the tree, he said. The roots run horizontally within the top four or five feet of the soil and can extend four to five times the distance of the canopy of the tree. That means a neighbor who puts herbicide on his lawn can affect your tree, he warned. If you must cut the roots, use a saw and paint the ends with a latex spray paint because of soil pathogens, he advised. When trimming limbs, cut at a slight angle just passed the branch collar or flair where it meets the trunk, he said. If the limb is long, cut it in pieces starting at the tip. Houser also asked the group to help in an attempt to locate trees at least 200 years old which have been bent to the ground and are attached. Some of these trees were bent by Native Americans to serve as markers and need to be preserved, he said.

Source: Mineola Monitor

Steve Houser is a Certified Arborist and currently the owner and President of Arborilogical Services, Inc.

Woodpecker Damage - Photo by James Solomon, USDA Forest Service

Arborists are often asked, “What is boring holes in a straight line across my tree’s trunk?”

The woodpecker is the culprit, and most of the time it causes no health problems for the tree. The most common woodpecker in our area is the Yellow-Bellied Sapsucker. This migratory bird can be identified by its medium size and distinctive markings. The adult birds are identified by a black crescent on the breast, pale yellow belly, white wing stripe, and a crimson crown. The male also has a crimson chin and throat, distinguishing him from the female whose chin and throat are white.

IDENTIFYING THE WOODPECKER DAMAGE

Typical damage can be a single row of small holes or several rows close together around the trunk or branches. Woodpeckers are drilling these holes to feed on sap and the insects attracted to it. Just because a woodpecker is feeding on a tree, does not mean the tree is infested with insects. Although some woodpeckers do feed on wood boring insects, bark lice and other pests harmful to trees.

Severe Woodpecker Damage: Minnesota Department of Natural Resources Archives

In severe cases, the rows of holes can be drilled so close together that entire patches of bark and wood are removed. If the tree is small and the damage is extensive, the tree could be girdled. This results in reducing the tree’s ability to transport water and nutrients, and the tree could die. This is rare, and most damage should not be a concern. Woodpeckers choose trees for no particular reason, but tree species with softer bark or high sugar content in their sap are favored. Some trees are repeatedly chosen over and over each year due to habit and migratory patterns.

MANAGEMENT OF WOODPECKER DAMAGE

Physical Repellents:

• Wrap burlap or other materials loosely around the area being tapped
• Smear a sticky repellent material on the affected area such as: Tanglefoot, Roost-No-More, or Bird Stop

Visual Repellents:

• Hang shiny metal objects (aluminum) or brightly colored plastics on or around the tree

Noise Repellents:

• Play bird distress calls or any other loud noises. Ex: propane cannons, fuse ropes, bird banger rockets, screamers, electronic scare devices or music.

In summary, it’s best not to worry about the damage already caused by woodpeckers. Instead, implementation of deterrents may be the best strategy in coping with further damage. This also aids in the prevention of any initial destruction.

The Migratory Bird Treaty Act prohibits the killing of woodpeckers without a permit.

References: North Central Forest Experiment Station, Forest Service, U.S. Department of Agriculture, St. Paul, Minnesota
Kentucky Department of Fish & Wildlife Resources