Professor Plum in the Conservatory

Article provided by Cindy Odgers …with the rope! Ever play a game of Clue? The game has suspense, intrigue and encourages players to solve a crime logically. Troubleshooting plant problems is a lot like a game of Clue except rather than discover a murderer, one must discover what or who is troubling one’s plants. Observing,

documenting and following the clues combined with logic and reasoning will typically lead to a solution (or solutions).

Inexperienced observers often think that they have encountered a serious problem, when, in fact, the “symptom” that alarms them is only a normal feature of a plant, a seasonal change in its appearance, or the sign of a nonparasitic agent. Distinguish what is normal and what is abnormal. Recognizing the appearance of healthy plants at different stages of growth and seasons is as important as recognizing the symptoms of particular disorders.

Most experienced plant problem solvers start with a check sheet or list of questions to follow when attempting to diagnose a plant problem. ALCA’s ACLP workshop on Plant Problems has an In-pocket Plant Diagnosis Checklist included on its resource page. Tools that can be helpful in collecting and recording information include but are not limited to a hand lens, trowel, knife, hand pruner, small saw, collecting bags both paper and plastic, tape measure, shovel or spade, soil auger or profile tube, soil-moisture meter and a camera.

The best tool to use when one begins, is a good pair of eyes. Observance is key to finding the answers and collecting the information being sought.

Name that plant. Correct identification of the plant in question is a must. • What does a healthy plant look like? • What are common problems if any for the plant? • What can be seen on the plant that does not look normal? Check out the leaves, stems, roots, fruit and flowers if appropriate. • What is the overall health of the plant? • Is the plant exhibiting signs (the presence of a biotic organism) or symptoms (plant response to an organism or abiotic issue)? • How do adjacent plants look? Are any plants exhibiting anything similar to the plant in question? • What is happening on site? • Who is responsible for the usual care of the plant that could provide information?

• When was the problem first observed? • When were signs or symptoms first noticed? • What is the cultural history of the plant? • What is the environmental history of the plant? • What does the owner think might be the problem? • Are there additional questions/thoughts once the previous questions have been answered? • Would samples (soil, water, tissue) be of use or value? • What other diagnostics could be helpful?

An important clue about the causes of symptoms are the patterns in which they occur across the site. Biotic or living agents such as insects, mites, fungi, bacteria, viruses and wildlife generally produce no uniformly repeated pattern of damage. Symptoms may be limited to one species of plant and the damage is progressive with time.

Abiotic (nonliving) problems develop from environmental (temperature, wind, moisture), site (soil, compaction), cultural (pruning, mower blight), chemical (spills or drift), or nutritional (excess or deficiency) problems resulting in damage that is likely on more than one species. Large areas of plants may be affected and damage often appears on leaves of a certain age.

If a solution is still not found, then a professional landscape diagnostician can help. A great resource is the University of Arizona’s Cooperative Extension Service.

Diagnosing plant problems can be challenging and some problems may be a combination of several factors. It is much easier to say what the problem is not, rather than what the problem is and not all plant problems can be solved. Sometimes the best solution is to remove the plant and replace it with a healthy plant selected for site compatibility and disease/pest resistance. However, in the majority of cases, one should be able to find a solution that works to return the plant back to a picture of good health!