Originally created 08/06/99

Plant sickness calls for detective work



Plants in the landscape cannot tell you what is wrong with them, 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 clearcut and easy to diagnose. They often involve a complex interaction of many different factors. In other words you have to be a detective.

When I talk to homeowners about plant problems, I ask many questions and try to narrow down the potential problems by the process of elimination.

Professional arborists say that most tree problems result from root stress caused by drought, root disturbance during construction, changes in grade and drainage, fill dirt over the roots or soil compaction.

When diagnosing a plant illness, make sure you have all the facts. Do not make snap judgments. The initial problem may not be the direct cause.

The perfect example is iron deficiency in azaleas. Iron deficiency is often exhibited by plants under moisture stress. An extremely wet soil literally suffocates the root system, then root rot organisms attack the damaged roots. The roots lose their ability to absorb nutrients like iron, and the leaves begin to lose color.

Attempting to cure this problem with liquid iron or iron supplements to the soil is a short-term solution. The best remedy would be to modify the drainage of the site or to transplant the azalea to a location that is known to drain well.

Poor cultural or management practices are a second major cause of plant problems. We can love our plants to death by applying luxurious quantities of fertilizer and water, or by spraying routinely, even when no pests are in the vicinity.

Planting too deep is another common mistake. When plants are set too deeply in the soil, the lower portion of the roots becomes deprived of oxygen and dies. Plants stressed in this manner often die a slow, agonizing death.

The most complex problems are those resulting from a combination of environmental factors and poor cultural practices.

Placing a shade-loving plant in the hot, baking afternoon sun without the benefit of irrigation will result in bleaching of the foliage. The immediate thought is that the plants are hungry, so a generous amount of fertilizer is applied. This only worsens the situation, and the plant eventually dies.

A magnifying glass or a white piece of paper would be a good tool to use when looking for insects, which are not always easy to see. When using the white paper, simply shake the plant over the paper and look for insects moving against the white background.

In summarizing, ask yourself several questions pertaining to your plant: Is my plant the right one for its location? What have the environmental conditions been? What fertilizers or chemicals have been applied? Are the dogs using this spot?

If these questions fail to yield a solution, call or take the plant to your county extension office, a garden center or a master gardener if you know one. In most instances, be prepared to answer a lot a questions similar to those I have discussed.

Sid Mullis is director of the University of Georgia Extension Service office for Richmond County. Call him at (706) 821-2349, or send e-mail to smullis@uga.edu. The Richmond and Columbia county offices have a Web page at www.griffin.peachnet.edu/ga/columbia.