One of the most common questions from customers to tree service providers is: “What’s wrong with my tree?” Just because it’s a common question doesn’t mean it’s easy to answer. That’s because there are many potential problems; the diagnosis process is not an easy thing to work through; the tree can’t speak and tell us where it hurts and, in many cases, more than one factor is responsible. However, your customers expect you to be able to figure out what’s wrong with a high degree of accuracy.
Diseases — pathogenic and otherwise
There are diseases, and then there are disease-like problems. Factors that cause symptoms that resemble a disease can be called diseases by the customer.
Pathogenic diseases are caused by living organisms, such as the fungi that cause dothistroma needle blight and apple scab. Bacteria such as Erwinia amylovora that causes fire blight can also be responsible for a reduction in tree vigor. Black canker of cherry is one example of a virus that can be problematic by limiting water movement in the cambium. Finally, mycoplasma-like organisms, such as the ones that cause ash yellows and elm yellows, are the fourth group of biotic diseases.
Disease-like problems are caused by a whole host of factors, sometimes referred to as abiotic. Dozens of contributing causes fall into this category, including compacted soils, planting depth, concrete covering the rootzone, heat, drought, soggy roots, high/low pH, salt, improper pesticide applications, etc. In my 30 years of experience as an arborist and horticulturist, more than half of the “sick” trees I’ve encountered have been ailing as a result of abiotic causes. As such, it’s wise to consider nonliving factors first, and pathogenic ones as a second possibility.
Paying for diagnosis
Two, maybe three main protocols exist for diagnosis.
First, the “toss it in free for the good customers or prospectively good customers with the hopes of getting a profitable job” approach. This is generally characterized by a recurring or potential customer contacting your company because their tree looks odd, the leaves are dropping off, or the car that they park near the tree has sticky stuff on the windshield and hood. Your receptionist takes down their name and address, tells them the technician will be right out and hands you the address. You tap the address into your GPS and go in search of the aforementioned sick tree.
Once at the property, the tree is examined, and considering all possible factors a diagnosis is arrived at and communicated to the client to discuss treatment options. In this scenario, the money to be made is based on the control measure, not the time and effort it took to diagnose the problem(s).
The second method, the “doctor or independent tree inspector” approach, is where inspection takes place and the inspector gets paid a reasonable rate for his/her time, while the actual work is subcontracted out to another company. This is similar to the medical doctor and pharmacist relationship. This is a good approach when independence or objectivity is important to the customer.
The third approach, a hybrid of the first and second, is where a division of your company inspects the tree and another division does the work. This arrangement works well for traditional tree services and parks/hospitals/apartment complexes/college campuses alike, providing a certain degree of objectivity as well as expediency.
Where to start
As simple as it sounds, the best place to start is with an accurate identification of the tree. Many site conditions, insect species and diseases are known to be associated with certain tree species. For example, in the Midwest, the pin oak is widely known to be affected by pH chlorosis. Knowing the tree species involved can help limit the number of possible causal agents.
Second, look for a pattern of normality or abnormality. Again, knowing the tree species and what it should look like is helpful. Bark peeling off might be problematic in the case of a canker, or it could be a part of the normal pattern of growth such as with eucalyptus, Scots pine, sycamore or river birch.
Because the unique conditions of the site commonly relate to the demise of many trees, it’s wise to take a few minutes to examine them. Notice items such as recently disturbed soils, applied road salts, mechanical injury to the trunk, cracks in the soil, health of the nearby turfgrass, slope, infiltration potential, and traffic from pedestrians or cars. A quick interview with a neighbor can yield volumes of useful information regarding the diagnosis.
Next, check the leaves. In addition to the presence of insects and spots, look for off-colors and twisted or curled leaves, which can be produced due to the effects of contact with herbicide drift. Lighter-than-normal foliage could indicate a lack of nutrients, while visible early fall leaf color could be the telltale symptom of root girdling or a lack of sufficient water movement in the vascular system.
What’s a sign and what’s a symptom? A sign is the actual presence of abiotic or biotic cause of the problem. Aphids, fungal fruiting bodies, soil particles tightly smashed together or tangled roots are examples of signs. Symptoms are the manifestation or the effects produced by the causal agent. Another way to describe symptoms is the visible response to the injurious cause. Examples of symptoms are wilting stems and branches, scorched leaves or stunted growth.
Semi-herbaceous parts of the plant such as stems/branches should be examined thoroughly for the presence of scales, scars, cankers and exposed tissues. While these obvious signs and symptoms are important, the rate of growth is just as important, if not more so. Take time to note the length of growth produced in the current year, the previous year and years prior. If 2 inches was produced in 2012, 4 in 2011 and 6 in 2010, a pattern of slowing down has developed and likely due to unsupportive site conditions, such as compacted soils or overwatering.
Trunks are commonly affected by canker diseases and internal heartwood rots, as well as the occasional wayward/intoxicated driver. About half of these cases are visible to the inspector, and half are internal. The bark often covers developing pathogens that can erupt, causing future problems. Probing the trunk with a piece of rebar or long screwdriver can be helpful in learning about what may not be initially obvious.
Instability in the tree is often caused by defects in the roots or root flare. When a tree trunk is observed without a flare at the interface with the soil, it is likely that the tree was planted too deeply, creating a tree that’s vulnerable to falling or at least struggling to survive. Considering that half of the tree’s tissue falls into this category, and the function of the root system is to absorb and transport nutrients and water, damage from heavy machinery can cause considerable health risk.
Tree diseases and abiotic disorders can be acute (occur within a short period of time) or chronic (occur over a long period of time). Further, more often than not, tree problems are caused by more than one factor. These two considerations can create a “double whammy” of sorts, where factor X stresses a tree, which leads to condition A, which makes it more susceptible to injury from factor Y that leads to condition B, spiraling into a variety of cumulative effects. For example, a white ash tree becomes stressed due to sunscald, which leads to heartwood decay, lessening its capacity to be structurally sound and increasing the likelihood that it may fall on a valuable target.
Monitor over time
Especially when working in the independent tree inspector role, the time involved will likely require significant involvement during the initial investigation, however, subsequent inspections may simply requires note taking and monitoring. The critical items to notice and document are changes over time. Two categories are commonly monitored; tree defects that don’t require immediate treatment, and treated trees that need to be observed for improvement following removal of the causal agent.
Examples of these categories are:
- A leaning tree, where the increase in degree of lean is calculated each season
- Spray applications to control sucking insects
At some point, each may need follow-up intervention, either to remove the hazardous tree or re-treat for future generations of pests.