Plant Health Care
Managing Abiotic & Biotic Disorders
PHC 101 - Key Concepts
Like humans, plants may let us know when they are feeling under the weather. While a seemingly healthy tree may fall over at any given time, there are often signs and/or symptoms that will develop which may communicate an issue to an arborist that is well-versed in the diagnostic process. Symptoms often prompt a tree owner to contact an arborist.
We are to determine if the issue at hand is caused by an abiotic or biotic influence. Often times, an abiotic issue is the primary problem which causes stress, which then brings on the biotic factors.
Sign - Physical evidence of the factor causing issues (fungi, insects, sawdust from insect feeding, mushrooms at the base of the tree, etc.).
Symptom - Plant response to the issues (leaf wilting, branch dieback, abnormal growing patterns, leaf discoloration, holes in leaves, etc.).
Abiotic - Non-living causal agent that results in negative plant response (soil compaction, drought, excess moisture, volcano mulching, etc.).
Biotic - Living-causal agent that results in negative plant response (insects, mites, other animals, and disease causing pathogens).
Managing Disorders, Maintaining Healthy Trees
We use the diagnostic process to determine what the primary culprit is when it comes to sick trees. After we determine all abiotic factors are managed to the best of our ability (soil properties, water management, mulching, etc.), we focus on the biotic issues and prescribe management procedures accordingly.
Below are the common categories of insects/mites and diseases along with some typical examples we’re seeing in our landscapes.
Insects/Mites
Chewing
Chewing insects have mouthparts that does exactly what their name implies. The symptoms are often simple, as the leaves appear to have been chewed on.
Japanese beetles, bagworms, eastern tent caterpillars
Sucking
Sucking insects (and mites fall into this category) have piercing mouthparts in which they insert them into succulent tissues to draw out sugars.
Scale, aphids, two-spotted spider mite, whiteflies
Boring
Boring insects (or borers) come in all forms. They are in common by the fact that they tunnel inside of the tree’s wood, cutting off vascular circulation.
Emerald ash borer, two-lined chestnut borer, shot hole borer
Gall-Making
These insects will cause the tree to produce masses, known as galls, when they “interact” with it - not usually through feeding, but egg-laying.
Gouty/horned oak gall, nipple gall, ash flower gall
Diseases
Foliar
Foliar diseases are caused by fungi or bacteria and will break down leaf tissue which defoliates the plant. Reoccurring leaf loss can be very stressful.
Apple scab, cedar-apple rust, needle cast, leaf blotch
Vascular
Vascular diseases are caused by fungi or bacteria and cause the tree to plug up its vascular system in an effort to stop the spread. These are often devastating.
Oak wilt, Dutch elm disease, bacterial leaf scorch
Canker
Cankers are sunken areas on tissues that disallow vascular flow in those localized areas. Many cankers on a single plant can be very problematic.
Phytophthora, hypoxylon canker, fire blight
Wood Decay
Wood decay is caused by fungal organisms that enter the tree through wounding and can break down the wood tissues.
Ganoderma, Pseudoinonotus, Armillaria, Kretzschmaria
PHC Management Tools
Through the diagnostic process, a stressor or pest may have been identified, such as some of the above examples - now what?
There are tools in the arborist tool kit that are used to manage stressors and pests in the landscape. The majority of these tools will be mechanical (physical) or chemical.
Sometimes we can simply mitigate environmental (or cultural issues) without specific tools and materials. Excess mulch, improper planting, improper irrigation, etc. can often be resolved on the spot after diagnosing the primary problem.
Soil Management - When soils are in poor shape there are things that can be done to improve them such as breaking up compaction and adding amendments such as compost and/or mulch.
Deep Root Fertilization - When soils are low in nutrition, a deep root fertilization can be employed to provide supplemental nutrition.
Systemic Applications - Materials can be applied to tree and shrubs systemically through injections, bark sprays, or soil applications.
Contact Applications - When plants need to be treated with precision timing, physically spraying them with proper materials can provide instant results.