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| UNIDENTIFIED STRESS PROBLEMS
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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!), 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
This publication contains pesticide recommendations. Changes in
pesticide regulations occur constantly, some materials mentioned may no
longer be available, and some uses may no longer be legal. All pesticides
distributed, sold, and/or applied in New York State must be registered
with the New York State Department of Environmental Conservation (DEC).
Questions concerning the legality and/or registration status for pesticide
use in New York State should be directed to the appropriate Cornell
Cooperative Extension Specialist or your regional DEC office.
READ THE LABEL BEFORE APPLYING ANY PESTICIDE.
__________________________________________________________________________________
The Plant Disease Diagnostic Clinic at Cornell
University is located at 334 Plant Science Building, Ithaca, NY,
14853. Phone: 607-255-7850, Fax: 607-255-4471, Email: kls13@cornell.edu |