Insect and Disease Problems
Improve your knowledge about insects and diseases that may affect tree health and learn proper steps for diagnosis.
By TreesAreGood®
International Society of Arboriculture
Threat to Tree Health
Insects and diseases can threaten a tree’s health. Once abnormalities in a tree’s appearance are noticed, a careful examination of the problem should begin. An arborist can help identify specific symptoms, try to diagnose the problem and select an appropriate treatment.
Stress
Sometimes the stresses trees experience in the landscape are more severe than they can handle and may make them more susceptible to certain insects and diseases.
Diagnosis
Correct diagnosis of plant health problems requires a careful examination of the situation. Many insects and diseases are plant-specific. Treatment without confirmation of the issue is often ineffective.
Insects
Some insects cause injury and damage to trees and shrubs. Generally, the insect problem is secondary to problems brought on by a stress disorder or pathogen. Most insects are beneficial rather than destructive. The following are categories of troublesome insects for trees.
Chewing Insects
Chewing insects eat plant tissue such as leaves, flowers, buds, roots, and twigs. Damage by these insects is often defined by uneven or broken margins on the leaves, skeletonization of the leaves, and leaf mining. The damage they cause will help in identifying the pest insect.
Sucking Insects
Sucking insects insert their beak into the tissues of leaves, twigs, branches, flowers, or fruit and then feed on the plant’s juices. Some examples are aphids, mealy bugs, and leafhoppers. Damage is often indicated by discoloration, wilting, spots, or general lack of vitality.
Borer Insects
Boring insects spend time feeding under the tree bark as larvae. Some borers also kill twigs and leaves, either when adults feed, or when larvae bore after hatching. Other borers, such as bark beetles, mate at or near the bark surface and lay eggs in tunnels beneath the bark.
Diseases
Three things are required for a disease to develop:
• A pathogen (disease-causing agent).
• A plant susceptibility to that particular pathogen.
• An environment suitable for disease development.
Pathogens
Plants vary in susceptibility to pathogens. Many disease-prevention programs focus on the use of pathogen-resistant plant varieties. Diseases can be classified into two broad categories: infectious and non-infectious.
Treatment
The treatment method used 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 an ISA Certified Arborist® about the nature of the problem or the proper treatment method to use.
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