US TREE SERVICE


Insects and diseases can threaten tree health. As soon as you notice any of the
problem. By identifying the specific symptoms of damage and understanding
their causes, you may be able to diagnose the problem and select an
appropriate treatment.

Stress

Basic elements that influence plant health include sufficient water and light, and a proper
balance of nutrients. Too much or too little of any of these environmental conditions may
cause plant stress.

Environmental stress weakens plants and makes them more susceptible to insect and
disease attack.

Trees deal with environmental stresses, such as shading and competition for water and
nutrients in their native environment, by adjusting their growth and development patterns
to reflect the availability of the resources. Although trees are adapted to living in stressful
conditions in nature, many times the stresses they experience in the landscape are more
than they can handle and may make them more susceptible to insects and diseases.

Diagnosis

Correct diagnosis of plant health problems requires a careful examination of the situation.

  1. Accurately identify the plant. Because many insects and diseases are plant-
    specific, this information can quickly limit the number of suspected diseases and
    disorders.
  2. Look for a pattern of abnormality. It may be helpful to compare the affected
    plant with other plants on the site, especially those of the same species.
    Differences in color or growth may present clues as to the source of the problem.
    Nonuniform damage patterns may indicate insects or diseases. Uniform damage
    over a large area (perhaps several plant species) usually indicates disorders
    caused by such factors as physical injury, poor drainage, or weather.
  3. Carefully examine the landscape. The history of the property and adjacent land
    may reveal many problems. The number of species affected may also help
    distinguish between infectious pathogens that are more plant-specific as compared
    to chemical or environmental factors that affect many different species. Most living
    pathogens take a relatively long time to spread throughout an area, so if a large
    percentage of plants becomes diseased virtually overnight, a pathogen is probably
    not involved.
  4. Examine the roots. Note their color: brown or black roots may signal problems.
    Brown roots often indicate dry soil conditions or the presence of toxic chemicals.
    Black roots usually reflect overly wet soil or the presence of root-rotting organisms.
  5. Check the trunk and branches. Examine the trunk thoroughly for wounds
    because they provide entrances for pathogens and wood-rotting organisms.
    Wounds can be caused by weather, fire, lawn mowers, and rodents, as well as a
    variety of other environmental and mechanical factors. Large defects may indicate
    a potentially hazardous tree.
  6. Note the position and appearance of affected leaves. Dead leaves at the top
    of the tree are usually the result of environmental or mechanical root stress.
    Twisted or curled leaves may indicate viral infection, insect feeding, or exposure to
    herbicides. The size and color of the foliage may tell a great deal about the plant’s
    condition. Make note of these and any other abnormalities.


Diseases

Three things are required for a disease to develop:


  • the presence of a pathogen (the disease-causing agent)
  • plant susceptibility to that particular pathogen
  • an environment suitable for disease development

Plants vary in susceptibility to pathogens. Many disease-prevention programs focus on
the use of pathogen-resistant plant varieties. Even if the pathogen is present and a
susceptible plant host is available, the proper environmental conditions must be present
over the correct period of time for the pathogen to infect the plant.

Diseases can be classified into two broad categories: those caused by infectious or living
agents (diseases) and those caused by noninfectious or nonliving agents (disorders).
Examples of infectious agents include fungi, viruses, and
bacteria. Noninfectious diseases, which account for 70 to 90
percent of all plant problems in urban areas, can be caused
by such factors as nutrient deficiencies, temperature
extremes, vandalism, pollutants, and fluctuations in
moisture. Noninfectious disorders often produce symptoms
similar to those caused by infectious diseases; therefore, it
is essential to distinguish between the two in order to give
proper treatment

Some insects can cause injury and damage to trees and shrubs. By defoliating trees
or sucking their sap, insects can retard plant growth. By boring into the trunk and
branches, they interfere with sap flow and weaken the tree structure. Insects may
alsocarry some plant diseases. In many cases, however, the insect problem is
secondary to problems brought on by a stress disorder or pathogen.


It is important to remember that most insects are beneficial rather than destructive.
They help with pollination or act as predators of more harmful species. Therefore,
killing all insects without regard to their kind and function can actually be detrimental
to tree health.



Insects may be divided into three categories according to their method of feeding:
chewing, sucking, or boring. Insects from each group have characteristic patterns of
damage that will help you determine the culprit and the proper treatment. Always
consult a tree care expert if you have any doubt about the nature of the insect
problem or the proper treatment
Chewing insects eat plant tissue such as leaves, flowers, buds, and twigs. Indications
of damage by these insects is often seen by uneven or broken margins on the leaves,
skeletonization of the leaves, and leaf mining. Chewing insects can be beetle adults or
larvae, moth larvae (caterpillars), and many other groups of insects. The damage they
cause (leaf notching, leaf mining, leaf skeletonizing, etc.) will help in identifying the pest
insect.

Sucking insects insert their beak (proboscis) into the tissues of leaves, twigs,
branches, flowers, or fruit and then feed on the plant’s juices. Some examples of sucking
insects are aphids, mealy bugs, thrips, and leafhoppers. Damage caused by these pests
is often indicated by discoloration, drooping, wilting, leaf spots (stippling), honeydew, or
general lack of vigor in the affected plant.

Boring insects spend time feeding somewhere beneath the bark of a tree as larvae.
Some borers kill twigs and leaders when adults feed or when eggs hatch into larvae that
bore into the stem and develop into adults. Other borers, known as bark beetles, mate
at or near the bark surface, and adults lay eggs in tunnels beneath the bark.

Treatment

The treatment method used for a particular insect or disease problem will depend on the
species involved, the extent of the problem, and a variety of other factors specific to the
situation and local regulations. Always consult a professional if you have any doubt
about the nature of the problem or proper treatment.
Insects & Disease Problems