Trees and shrubs are dynamic living organisms periodically attacked by pests, diseases and environmental stressors. To keep landscape plants in good health tree and shrub disorders must be properly diagnosed and treated. A plant disorder is any condition that interferes with normal growth and development. The most critical element of diagnosing a plant disorder is to determine the base cause of the problem. This is done by analyzing signs (evidence of pest/disease) and symptoms (observed abnormalities) on the affected plant. The causes of tree and shrub disorders are classified as biotic (living) or abiotic (non-living) and commonly result from more than one causal agent further complicating the diagnosis process. After an accurate diagnosis is derived treatment options should begin with efforts to change the plant’s growing environment (cultural control) to reduce limiting factors of growth. Where cultural control is found insufficient the use of biological and chemical control are considered. Modern plant health care targets preventative strategies and suppression rather than eradication. This approach involves communication with clients on options, advantages, environmental impact and treatment effectiveness.
Process for Diagnosis
- Identify the plant species
- Observe and note visual signs and symptoms on and about the plant
- Gather information (site, weather, maintenance practices, landscape layout, recent site changes, etc.)
- Consult references and specialists if needed
- Match what we know to what we see
- Arrive at a diagnosis
- Prescribe treatment options
Methods of Treatment
- Cultural control – selection of suitable plants; improving soil health by balancing pH and correcting nutrient deficiencies; mulching and proper irrigation, pruning to promote better growth.
- Biological control – suppressing pest populations using beneficial insects and fungi.
- Chemical control – suppressing pest population using pesticides: herbicides, pesticides, fungicides, etc.
- Alternatives to pesticides – soaps, horticultural oils, and insect growth regulators
- Mechanical management – physical removal of a pest from a plant such as blowing it off with water spray, installing physical barriers, and physical removal of an infested plant part.
Qualifications to Diagnose and Treat Trees and Shrubs
Diagnosing and treating plant disorders is a technical procedure relying on training, experience, keen observation, and knowing when to call upon outside resources. Skills of plant identification, plant biology, and plant stress response along with knowledge of common pests are essential to achieve an accurate diagnosis and treatment prescription. An ISA Certified Arborist is extensively trained in the technical elements of diagnosis and treatment of tree and shrub disorders and held to a continuing education requirement. Arborists applying chemicals are required to hold a Commercial Chemical Applicators License in their respective state. All tree and shrub treatment work performed by an arborist shall be completed in compliance with federal and state chemical application laws and the Z133.1 safety standard.