Trees & Shrubs

What's wrong with my plant? How can I avoid this problem again in the future? These common questions are the first of many to ask when diagnosing tree and shrub problems. While sometimes the cause of plant problems are obvious (i.e., seeing the deer eat your plants), many problems demand a more lengthy investigation. Diagnosing tree and shrub problems is much like putting a puzzle together. Many pieces need to be gathered and brought together before assembling the finished product.

Fortunately, there is a useful guide for assembling the pieces:

* Diagnosing Plant Damage (Arizona State Extension) is equipped with helpful examples that illustrate the steps in diagnosing plant damage.

Experts agree that it takes practice to diagnose plant problems well. Gathering information about the plant, its problems, and the site requires asking good questions or making good observations. Each diagnostic effort will likely deliver new questions. Remember, there is no one set of good questions to ask, but the following article may be a helpful source for asking diagnostic questions related to trees and shrubs:

* Recognizing tree and shrub diseases (University of Missouri Extension). Notice this article asks many questions in an effort to obtain helpful information to identify the problem. You may want to print this article and use it as a guide for asking questions as part of the plant diagnostic process.

When diagnosing tree and shrub problems, it is helpful to begin with an idea of possible problems that could affect the plant. The following resources are good overviews of problems commonly affecting plants in the landscape:

* Trees and Shrubs: Diseases, Insects, and Other Problems (Sustainable Urban Landscape Information Series, University of Minnesota) is an overview for tree and shrub problems in the landscape.

Sometimes the onset of tree and shrub problems happens quickly, and sometimes woody plants decline gradually over weeks, months, or years.

See:

* Decline and Dieback of Trees and Shrubs (University of Illinois Extension). This report covers symptoms, causes, identification, and control for decline and dieback of trees and shrubs. Note that decline or dieback of trees and shrubs can arise from biotic (living) factors, abiotic (nonliving) factors, or a combination of biotic and abiotic factors. You may notice even when a particular cause of decline is not identified, using good cultural and management practices are essential for reducing the rate of decline or preventing further problems from developing.

Insects and diseases are living agents that need nutrition so they, too, can live and reproduce. Sometimes tree and shrub problems caused by insect and disease can be avoided or managed by selecting resistant varieties or maintaining a healthy plant. On the other hand, there are times when insects and disease damage trees and shrubs even when we plan to minimize their opportunities.

Trees and shrubs in the landscape often have to tolerate less than ideal conditions, making them more vulnerable to insects and diseases. The reality is that insects and disease do affect woody plants. Understanding how biotic factors affect trees and shrubs, identifying the causal organism(s), and implementing control strategies are essential in managing tree and shrub insect and disease problems in the landscape.

* Diseases and Insects (Sustainable Urban Landscape Information Series, University of Minnesota) discusses managing insects and disease on plants.