Plant Problem Diagnosis

How to know what's really going on so you can fix it

Box Elder bug
Box Elder Bug

Whether you are a seasoned gardener with years of experience under your belt or just getting started, gardening mishaps, sickness, and fatalities are going to occur in your yard. Finding the correct solution for problems depends on how closely your observe what is going on. Look at not just with the plant, but its environment including other nearby plants and its location as well as a variety of cultural factors. Often, the problem is more than what meets the eye and sometimes the best solution is taking no action at all. It all depends on making an accurate diagnosis.

What is the root cause?

Plant problems can stem from critters, fungi, bacteria, or viruses, or from storm damage, temperature extremes, and the misapplication of chemicals. Often a symptom may be secondary to the original cause. For example, a plant not receiving the correct nutrients in the proper amounts may become weak and more susceptible to infestations of pathogens specific to that plant. Until the underlying cause is addressed, the chances that you'll be able to eradicate the pest or disease is unlikely. Occasionally, you'll discover that there isn't a problem at all and the condition is actually normal for that plant under those circumstances.

The first step is finding out as much as you can about the plant in question. What is the genus, species, and variety? What is it supposed to look like? How does it grow in your climate? If you have a young tree that you just planted and it's leaves suddenly yellow and drop, it could be a problem if it's May, but that would be perfectly normal in October. Believe it or not, misunderstanding what can be expected of specific plants in various environments is extremely common. If you move from one climate to another, you may plant the same variety in each location and see completely different performance.

Analyze the abnormality or problem. What are the signs and symptoms? Signs are evidence of something that should not be there. Symptoms are the reaction of the plant. Slug slime is a sign. Leaf drop is a symptom. Neither symptoms nor signs alone necessarily lead to a correct diagnosis. Often the symptoms show up far from the source of the problem. Leaf drop may be caused by inadequate moisture or a damaged root system. Compare your plant with a normal, healthy plant of the same variety to obtain additional clues.

Look for patterns

Damage patterns can provide vital clues to what is happening with your plant. Irregular, random damage often indicates the presence of a living organism such as insects or fungi whereas regular patterns are more likely to be caused by nonliving agents such as storm damage, inadequate moisture, too much moisture, freezing, or chemicals including fertilizers. Even air pollution can cause tip burn on conifers, which may result in uniform damage to each needle.

Damage and the time factor

If the problem appears suddenly, it's often a clue that the culprit is nonliving. The usual suspects include extreme weather conditions such as very high heat when new growth occurs, freezing temperatures when a plant is not dormant, animal or bird damage, and chemicals to name just a few. However, a plant that is already compromised by disease may be more susceptible to mechanical damage.

Damage that occurs gradually is more likely to be caused by some type of live agent. It takes time for borers, weevils, and verticillium wilt to do enough damage for you to see symptoms of decline. You may notice a progression of a problem as it spreads from one individual to others. One plant may be dead, another may be in a stage that your dead plant just passed through, while a third displays the first signs. With living causes, you are more likely to see this type of progressive decline over time.

Causes of plant disease or damage

The Who's Who of plant disease and damage is the subject of entire books. Start with questions ... many questions. Don't assume anything. The more systematic you can be, the more likely you'll narrow the problem down to the correct cause.

The majority of the time the problem is caused by something other than bugs or disease. Once you've narrowed your options to living or nonliving causes, you can focus more specifically on the source of the problem. For example, if you've noticed that there are light green patches on an otherwise healthy lawn in both the front and backyard, that appear suddenly and all at once, and are more or less the same shape, then you have a few clues. Many times, especially with the best of intentions, the gardener is the source of the problem. Thinking back a couple weeks you might remember applying fertilizer and having a problem with getting an even distribution. The probability is good that the grass was burned when fertilizer was applied. This is something of an oversimplification, but serves to illustrate the point.

Every problem is a combination of signs and symptoms. Not even the most knowledgeable gardener has all the answers, so finding solutions to more daunting problems dealing such as with viruses, fungus, or insects often requires a few good books and other gardeners.

Finding help

In addition to the many excellent gardening books available, you can take advantage of other resources. If you haven't the time or inclination to figure out what the problem is, there are some good sources to check for more information.

The key to discerning how accurate the information, is how many questions the interviewer asks. Regardless of source, be wary of ad hoc advice without a thorough analysis. If possible, provide as much material as possible including photos, plant samples, and other evidence. Be prepared to answer questions about location, cultivation, and any measures you may already have taken.


To get more time in the garden, hire a reputable landscape service through NextStep Remodeling .

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