Tree Assessment Guidelines
PLANT PROBLEMS INVESTIGATIVE GUIDELINES
- With the help of the property owner or manager, determine the primary complaint and obtain a full description of the problem. Get a history of the site, construction or other factors that may have had an impact on the plantings.
- Determine time frame for the appearance and progression of the problem.
- Identify the plant and review common potential pests, diseases and environmental disorders. (UC IPM and other resources)
- View the entire tree and site, and surrounding plantings, not only a closeup view of the specific damage.
- Try to determine if the origin of the problem is in the foliar canopy, trunk, root system or a result of environmental and management conditions. Often a foliar die-back condition is the result of root loss or drought stress.
- Look around the property and the nearby properties for indicators of common problems or contributing factors. Especially look on the other side of an adjacent fenceline into the neighboring property. Neighbor plantings and irrigation could be directly affecting the subject tree.
- Assess growing conditions, compatibility of plantings and irrigation program, soil and water management.
- Inspect for pest presence and typical feeding damage, missing or distorted plant parts, leaf surface scarification or chewing of leaf margins.
- Differentiation of fungal vs bacterial disease, may be somewhat obvious from the geographical location and prevalent diseases, landscape management and characteristics of the causal pathogen, but may not be definitive without pathology lab analysis. The identification of exact disease organism may not be necessary because suppressive and preventive treatment is often similar.
ASSESSING TREE AND SHRUB FOLIAGE AND THE FOLIAR CROWN
- Foliar canopy decline, central leader and lateral branch die-back, or stunting of leaf size and annual shoot growth, pale and yellow discoloration is often the result of poor growing conditions, poor soil and water management, root decay or mechanical damage, soil compaction, pavement, restricted soil volume, and chemical and fertility issues that negatively affect the beneficial soil biology and plant nutrition.
- Branch breakage, partial fractures or girdling can result in drying/browning of foliage and die-back that may resemble a disease condition. This can be the result of over-weighted branches, wind or mechanical damage. Calcium and related mineral deficiency/imbalance can contribute to weakened cell-wall strength and structural failures. Lightning strikes cause blackening, branch die-back, wood fractures with possible leader or limb breakage.
- Leaf damage, spotting, discoloration, dry/dead tissue, or a more serious defoliation can be caused leaf and twig blights, vascular fungal and bacterial disease, environmental factors like water-deficit/drought-stress, wind-related desiccation, sun-scald, hail or frost. Fire in understory plants can scorch or burn the tree foliage above.
- Less severe signs of holes in leaves, scarification or stippling of leaf surfaces, chewed leaf margins and tunneling, as well as characteristic discoloration are often a result of pest activity. Chewing, sucking, rasping and leaf mining arthropod pests damage and discolor foliage. The presence of insects on foliage or stems does not necessarily indicate a problem, unless there is active or known potential damage to the plants.
- Discoloration patterns like spotting, mottling, yellowing of leaves can be due to nutrient deficiencies, excesses, imbalances.
- Fungal or bacterial disease also can cause discoloration, spots and holes and premature leaf drop. Advanced severe disease can cause branch die-back and tree mortality.
ASSESSING TREE TRUNK AND ROOT COLLAR
Mechanical damage to tree trunk and root flare is common from construction and grading equipment, lawn mowers and string or blade trimmers. Poor pruning cuts, sub-standard cable support attachments and staking ties, chain-saws, gun shots, arrows, axe and machete hacking, chains and chokers, can cause serious wounds, impair growth and conduction of water and nutrients, and open avenues for infection.
Removing/raising the lower foliar canopy exposes tree trunks to drying, sun-scald bark damage and necrosis of the underlying live tissue. Similar damage is done by extreme “stylized” or “aesthetic” pruning practices (espalier, pleaching, pollarding, bonsai/niwaki, and fruit tree “open-center” pruning, when woody stems are exposed to direct afternoon sun.
Beetle borers and invasive moth larvae can cause mild to severe damage to tree and shrub trunks and surface roots, resulting in holes, bark disfigurement or extensive galleries that destroy the growing layer and conductive tissue. Signs of beetle and moth activity will often include “frass” (a fine powdery sawdust or granular droppings), and sap exudations associated with the pest entry/exit holes. Some borers are carriers/vectors of fungal disease which is introduced into the tree vascular and structural tissues when the pest enters through the protective bark covering.
Signs of fungal, bacterial and water-mold disease can occur on the trunk and at the root collar when active infections are present. Discoloration, abnormal bulges/growths, fungal conks and mushrooms, bleeding cankers on trunk and/or root collar, frothy or runny substance on limbs or tree trunks, can be signs of disease or environmental stress disorders.
BELOW GRADE ASSESSMENT OF ROOT CROWN AND ROOT SYSTEM
The possibilities for below soil grade inspection of a tree root system are limited. Direct visual assessment of roots and root crown requires digging or pneumatic ‘air-spade’ excavation. Major lateral roots can be located with ground penetrating radar, or sonic tomography, but presence and extent of decay cannot be determined without excavation.
Therefore, the arborist often must rely on “educated guess-work” and deduction of possibilities in determination of possible root problems. Restricted soil surface and volume, such as with overgrown container plantings and ‘hardscapes’, can be a significant cause of restrictions in expansive root growth, girdling roots, and nutrient depletion. Soil compaction and pavement limit aeration of soil and roots and prevent the development and maintenance of a diverse and healthy soil microbiome. Poor soil fertility and water management can contribute to root rot and crown rot disease.
The experienced arborist must take these conditions into consideration as possible contributing factors to foliar decline and die-back, bleeding cankers, bark discoloration, structural depressions and cavities indicating and decay of the root collar and/or tree trunk.
TREE STRUCTURAL DEFECTS AND HAZARDS - RISK ASSESSMENT
Tree Hazards and Risk Assessment, an article by Don Cox
RESOURCES FOR CALIFORNIA GARDENERS AND TREE CARE PROFESSIONALS