(This article has been adapted and edited for applicability to Bonsai, with permission, by Ted Groszkiewicz)

Plants may not be able to talk, but they will let you know when they are sick. Wilted or discolored leaves, leaf spots, dying branches and premature leaf drop are just a few of the common symptoms of plant stress. Unfortunately, plant problems are not always clear-cut and easy to diagnose. They often involve a complex interaction of many different factors.

According to plant pathologists at the UGA plant diagnostic clinic, the majority of disease problems can be directly attributed to environmental stress, such as excessive moisture, heat or drought. These factors weaken plants and make them more susceptible to disease and insect pests.

Professional arborists say that most tree problems result from stress of the root system imposed by such things as drought, root disturbance during construction, changes in grade and drainage, fill dirt over the roots, soil compaction, etc. (In the area of handling roots, bonsai enthusiasts learn early on how to handle root systems at the proper time of the year for the species of plant material being used to style bonsai )

When attempting to diagnose a plant illness make certain you gather all the facts that may have led to the problem and give the plant a thorough physical examination before attempting a cure. Never make snap judgements because the problem you perceive at first glance may not be the direct cause. Consider iron deficiency, for instance, on azaleas. Plants under moisture stress often exhibit iron deficiency. An extremely wet soil literally suffocates the root system. As a result, root rot organisms attack the damaged roots. The roots lose their ability to absorb nutrients like iron, and interveinal chlorosis is clearly exhibited by the leaves. Attempting to cure this problem with liquid iron or iron supplements to the soil is only a short term solution. The best remedy would be to modify the drainage of the site (container for bonsai) or to transplant the azalea to another location known to be well-drained ( for bonsai, into another container with a better draining soil mix).

The second major cause of plant problems is poor cultural or management practices. We can literally love our plants to death by applying luxurious quantities of fertilizer and water or by spraying routinely even when there are no pests in the vicinity. (For some reason I find that many bonsai enthusiasts enter a phase, sometimes prolonged, of deeply caring for their plants to the extent that their TLC results in dead plants as mentioned above.) Planting too deep is another common cultural mistake. When plants are set too deeply in the soil ( even in a bonsai container), the lower portion of the root system can become deprived of oxygen and dies. Plants stressed in this manner often die a slow, agonizing death.

The most complex problems to diagnose are those resulting from a combination of environmental factors and poor cultural practices. Placing rhododendrons in hot baking afternoon sun without the benefit of irrigation will result in the bleaching of foliage. (This is also true of azaleas, rhododendrons and other broad-leaved evergreens that are exposed in a similar manner without irrigation.) The immediate reaction to this problem is that the plants are hungry, so a generous amount of fertilizer is applied in an attempt to snap the plants out of this problem. Unfortunately, this practice adds insult to injury and the plants eventually die. But what if you examine the plants in the morning hours when they are fully shaded and the client swears he did nothing out of the ordinary to the plants? Remember, the client is always innocent until proven guilty.

The best advice when diagnosing a plant problem is to approach it in a logical step-by-step sequence, gathering all the clues along the way. The following is my five step method for approaching a plant problem. It works for me.

Step 1: Identify the plant. You don't need to know the precise botanical name of the plant, but simply the type of plant it is. Then begin to analyze the types of problems that type of plant often encounters. If the plant is a juniper, for instance, you can frequently suspect three problems: spider mites (look for them with a hand lens working on the inside foliage); juniper twig blight (look for twig die-back from the tips and black spores with the hand lens); and wet-feet (junipers cannot tolerate poorly drained soil).

Step 2: Check the Environment of the Area. What has been the weather patterns prior to the problem? Has there been an ice storm, a drought or a deep freeze? Are other plants in the general area showing the same symptoms, or is this an isolated case? What is the drainage like on the site? (For bonsai, the container soil may have become waterlogged?) Are there any chunks of mortar or lime-rock in the soil that may be elevating the pH level? (It is possible that too much dolomitic limestone may have been added to the container soil for bonsai.)

Step 3: Ask questions. You'll be surprised how much you can learn about the recent past of the plant just by asking questions about cultural practices. (As a bonsai enthusiast you can ask yourself these questions.) Has the plant been fertilized recently, pruned recently, or sprayed with some sort of chemical? Were there any chemical spills recently near the plants? Are there may long-legged dogs in the neighborhood? Etc., etc.

Step 4: Be Prepared to Take Samples. Put together a simple diagnostic kit and carry it with you when visiting clients (or when checking your own landscape or bonsai plants). The kit should consist of the following items:

1. A Ziploc Bag for preserving fresh leaf samples or for keeping a root sample moist if it is to be analyzed for nematodes. (This is a must if you have to send samples off for diagnosis through your County Extension Office.)

2. A Knife for checking to see if the plant is still alive after a severe freeze. A green cambium below the outer bark indicates that the plant is still alive. A knife is also useful for digging out insect larvae, such as the peach tree borer in areas where sap is protruding from the main trunk. This is not the cure for the problem, but an excellent way to show the client what the problem is. (If you don't recognize the insect problem, check with your County Extension Office for a possible I.D. or have the sample sent to the Entomology Department through your Extension Office for an I.D.)

3. A Magnifying Glass is useful for seeing tiny insects, such as mites and thrips that may be difficult to see with the naked eye. Most variety drug stores and art supply stores sell magnifying glasses. Try to get one with at least 3X magnification.

4. A Soil Sample Bag is always handy if a soil sample is deemed necessary. (These are available through the County Extension Offices in Georgia (and other States.)) There is a minimal charge for a routine soil sample. Soil-less mixes (formulas) carry an extra charge. Check with your local Extension Office.

5. A White Note Card is useful for detecting tiny insects such as flower thrips and mites. Simply shake the plant part over the white card and look for the insects moving against the white background.

Step 5: Focus on the plant. Look at the leaves for signs of insect or disease damage. Distinct brown spots on the leaves surrounded by a dark halo may indicate a disease problem. A foliar scorching often indicates a root problem (excessive moisture, over-fertilization, drought, etc.). Inspect the stems and branches for swollen areas or cankers, insect punctures, sap flowing from insect entry holes, or mechanical damage to the trunk. Then look at the root system for signs of decay. White fibrous roots should be evident near the drip like or tip of the canopy. (Remove the bonsai from the container and check the root system; the white fibrous roots should be evident around the root-ball which makes contact with the interior of the container.) If the roots appear brown and decayed, look closer at the planting site for a possible cause. (For bonsai check the container soil and condition of roots for a possible cause.)

So be a detective when attempting to solve a plant problem. Know the plant, its cultural requirements and common problems. Survey the site, ask questions, take samples if necessary, and check the weather records and give the plant a thorough check-up. Remember that the symptoms you first perceive may not be the primary cause of the problem. By approaching the problem in a methodical fashion, you may not be correct in your diagnosis all the time, but you will be correct most of the time.