What is Killing My Tree?
Most tree problems result from combinations of factors. When the cause of a health problem is not obvious, there are always clues that can help with diagnosis. However, a satisfactory explanation may involve several factors. Often some abiotic (nonliving) influence, such as drought, makes trees more susceptible to invasion by biotic (living) agents such as fungi and insects. The following guidelines should be helpful when diagnosing tree problems.
- Problems caused by physical, chemical and environmental factors usually affect most or all plant species present. Problems caused by organisms seldom affect more than a few species, and often just one.
- Symptoms caused by organisms usually vary in space and develop over time. Symptoms that appear suddenly, are relatively uniform and stabilize quickly, are probably not caused by an insect or disease organism.
- Symptoms that seem to be associated with aspect, exposure, drainage or disturbance are very likely to involve an important environmental component; but organisms could still be the primary agent(s).
- Check with a magnifying glass before ruling out organisms. Look for frass, silk, eggs, shed skins, holes, or life stages of mites and small insects. If you suspect fungus infection look for fruiting bodies, lesions, cankers, resin or sap flow, resin soaking of stems or roots, or sapwood stain near the transition between healthy and diseased tissue.
Genetic factors can have a noticeable effect on tree response to adverse conditions. Symptoms of ozone injury and needle cast infection, for example, can vary greatly among trees of the same species growing right next to each other.
Wilting indicates that water is not moving through the tree fast enough. The most common causes of wilting are root disease, vascular disease and drought. Vascular disease is usually caused by microorganisms; root disease can stem from physical or chemical injury, excess moisture, infection by microorganisms, and feeding by various animals.
Primary Causes verses Secondary Infestation
Symptoms often result from the effects of secondary agents, not the primary agent. Trees weakened by adverse weather, unfavorable site conditions, injury, competition or advanced age become more susceptible to infections and infestations by secondary organisms. Treatment related to these secondary agents will provide temporary benefits at best, unless the primary problem is also addressed.
How bad is it?
Agents that affect only foliage are unlikely, in themselves, to result in tree mortality. However, they can reduce growth and predispose trees to other problems. Agents that affect only heartwood (e.g., some decay fungi) can increase the likelihood of stem breakage, and can make trees unmerchantable, but they might have little effect on tree life span.
Healthy buds support a prognosis of recovery; dead or unhealthy buds suggest that recovery is unlikely.
For help diagnosing problems plaguing ornamental trees in residential landscapes contact the office of Penn State Cooperative Extension in your county. The International Society of Arboriculture maintains a database of certified arborists trained in the art and science of planting, caring for, and maintaining individual trees.
If your woodlot or forest land shows signs of pest or disease damage contact the DCNR-Bureau of Forestry service forester for your county.