Insects
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 also carry 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 many 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 and shrub health.
Insects
may be divided into three categories according to their method
of feeding: chewing, sucking, and boring. Insects from each
group have characteristic patterns of damage that will help
determine the culprit and the proper treatment. Contact your
Wood Acres Certified Arborist to determine the nature of the
insect problem and the proper treatment.
Chewing insects
eat plant tissue such as leaves, flowers, buds, and twigs.
The 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, mealybugs,
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:
All pests in this category 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.
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 and 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. |
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