Trees and Invasive species

If you are trying to grow the perfect tree, or at least a healthy and beautiful tree, battling invasive species or potential invasive species can be a challenge.

An invasive species, also called a pathogen, can infect a tree anywhere from the stem to the branches and quickly kill the bark in a spreading canker. These pathogens reproduce rapidly with a huge a numbers of spores. The spores can be shot into the air and carried by the wind, or carried by the splash of a raindrop, a bird or insect.

Non-native, invasive species constitute one of the greatest economic and environmental challenges in the history of the United States natural and managed ecosystems. Non-native plants and plant pests cost more than $100 billion per year in crop and timber losses plus the expense of herbicides and pesticides. Types of invasive species include:
* chestnut blight * sudden oak death * white pine blister rust * beech bark disease * dutch elm disease * butternut canker * Port-Orford-Cedar root disease * dogwood anthracnose

It is difficult to recognize tree diseases because the organisms responsible are small and not easily detected in the early disease stages. Once a problem is recognized, the disease is often in an advanced stage, limiting an arborist’s treatment options. Some diseases can kill trees in a short period of time (oak wilt infections); others are long-term chronic diseases (nectria canker).

Some diseases do not usually cause serious damage to trees (powdery mildew), while others can virtually eliminate an entire tree species (chestnut blight, Dutch elm disease). Harmful, parasitic bacteria cause a number of plant diseases. Damage from bacteria can be limited to leaves (shot hole disease) or the bacteria can infect and destroy the vascular system of the tree (bacterial leaf scorch), eventually causing tree death.

A tree owner may first notice a problem with their tree when leaves in a section of the crown begin showing signs of wilting or scorching. Arborists can pick up on more subtle clues. Often an upper portion of the crown shows signs first. With verticillium wilt, one limb or a group of limbs show signs of a problem before the rest of the tree. Other symptoms to look for include: trees of the same species that express themselves differently; wilting or scorching leaves; leaves smaller than normal in one section or the whole tree; early fall color in one section of the tree or the whole tree; dieback of twigs and limbs; reduced shoot growth; leaf discoloration; stress-induced production of numerous small cones or fruit of poor quality; and heavy resin or gum flows.

Extensive dieback and death can occur rapidly in the case of Dutch elm disease, oak wilt of red oaks, or blue-stain wilt of shortleaf and loblolly pines. In the case of bacterial leaf scorch, oak wilt of white oaks, and verticillium wilt, damage occurs more slowly and often can be controlled. When a tree has been infected, a professional arborist can assess treatment protocols and advise techniques for mitigating damage or avoiding a repeat of the infection.

Of course, the best way to avoid tree diseases is to keep trees healthy, which makes them less susceptible. Insects that spread diseases are attracted to trees that are stressed and have a weakened defense system.

A professional arborist can assess and maintain a landscape, ensuring proper soil fertility and watering practices to promote plant health and minimize the effects of stress on plants. Arborists can also help diagnose and mitigate other causes of poor growth or decline, such as poor site conditions or mechanical, environmental, and chemical injuries.

Like anything, sometimes it is important to call in a professional to help and this includes tree disease as well.

Andrew Johnson is the owner of Central Texas Tree Care, a leading tree service provider in Central Texas (Travis County and surrounding areas) offering services such as pruning and removals, cabling and bracing as well as arborist reports, diagnostics, pest management, fertilization and Austin tree service trusts. For more information please visit http://www.centraltexastreecare.com.