UNIDENTIFIED STRESS PROBLEMS   F A C T S H E E T

When a tree or shrub is diagnosed with a secondary fungal canker/dieback or leaf/needle fungus, this indicates that the plant tissue being colonized is under stress from another cause. These kinds of plant pathogens usually do not attack otherwise healthy plants. Most often the primary cause of the stress is not diagnosable based on plant samples submitted. Improper cultural practices, soil characteristics, weather extremes, insect problems, stem/trunk canker problems, root rots, etc., or a combination of any of the above, are just some of the potential primary causes for such plant stress.

When the primary cause of the plant stress is unknown, recommendations include practices aimed at keeping the vigor level of the plant as high as possible. These include:

1) Water as needed. Plants need an inch of water/rain per week during the growing season; if droughty conditions develop, make sure the plant gets at least this amount of water. Use a rain gauge to determine how much water is actually being received by the plant.

2) Fertilize as needed. Use a balanced fertilizer; ideally a soil nutrient analysis should be performed to determine specifically what, if any fertilizers, are needed.

3) Avoid soil compaction around the plant (no swing sets, picnic tables, etc. near by!), and avoid mechanically wounding the plants (weed whacker damage, lawn mower damage, swings or dog runs bolted to the tree, etc.). Aerate the soil if compaction is a problem.

4) Make sure other obvious insect and disease problems are taken care of (defoliators, leaf spot fungi, etc.).

5) Conduct a general site assessment to make sure the plant is growing in the proper site (for example, yew plants do not tolerate wet soil conditions; azaleas and rhododendrons need acid soil conditions to thrive; plants that normally grow as understory shrubs do not thrive in open, unshaded areas); etc. If the site is not proper for the plant, consider replacing it with a plant better suited to the area. Also check the hardiness of more "exotic" plants to make sure they can survive local conditions.

Last updated, KLS, 11/99