In all our Forestry Extension programs, we try hard to develop the concept that woodland health is a overall condition, and that many very healthy woodlands have individual dead or dying trees. Some would even argue that a woodland must have dead trees to be really "healthy" because some processesand animal residents of the forest ecosystem depend on them for food or shelter.

However, it is natural for a woodland owner to get concerned when several trees start dying, or a homeowner's yard tree turns brown, and we in Extension often get calls to see if we can explain what is going on. Around residential areas there is the added concern for life and property: sick or dead trees that might have no negative impacts in a natural or managed woodland property might be a serious danger in a residential setting.

Diagnosing the problem

If you have a tree that appears to be dying or is dead, or it just doesn't "look right," we encourage you to use this website to help diagnose the problem and identify a remedy, if any. See the diagnosis page. If you are still stumped, feel free to call the Extension office at 776-7371 for assistance in diagnosis. However, be aware that it's often difficult to make a firm diagnosis over the phone, and we are seldom able to make field visits. You may bring a sample from the affected tree to the Master Gardener plant clinic. Call 776-7371 for clinic hours. Samples may also be left for the Extension forestry agent.

It's a "pine" tree...I think

A key to accurate diagnosis is knowing what kind of tree is involved. Many insect and disease problems are host-specific, i.e., they affect one or a few closely related species, and not others. Know your host! If your tree identification skills need work, OSU's Trees of the Pacific Northwest website is a great place to start.

Insect or disease "infestations" are seldom the problem

In southern Oregon, pest infestations that sweep across the countryside are seldom the issue. Many, if not most, sick tree problems are actually related to underlying stresses that reduce the tree's vigor and make it vulnerable to pathogens. Typical stresses include: Drought; competition with surrounding trees and brush for limited resources, usually soil moisture; shallow, rocky soils; south and westerly aspects; heavy clay soils; mechanical damage to tree trunks; damage from fire; sudden exposure of shade-grown trees to intense sunlight; soil compaction; trenching; backfilling over the existing soil surface; poorly drained soils; over-watering; flooding; etc. Thus, while insects or diseases may be the DIRECT cause of tree death, the UNDERLYING cause is usually related to one of these stress factors.

Sick tree articles and information

Overview of common Pine problems

Overview of common Fir problems

Overview of common Incense Cedar problems

Overview of common Madrone problems

Forest health conditons in Oregon - 2002. Overview of key problems around the state.
Aerial survey maps. Maps of aerial surveys for insect and disease problems - includes coverage of southern Oregon.
Why is my tree dying? And what can I do about it? (brief article)
Dead brances, dead tops, and dead Douglas-fir trees - the interaction of water stress, insects, and disease. Written in 1999 by the Oregon Department of Forestry, about conditions that year, but very applicable today. Excellent overview of the interaction of stress factors and insect and disease problems. Good photos too.

The best websites

SWOFIDSC - SW Oregon Forest Insect and Disease Service Center. Detailed information about bark beetles, root diseases, mistletoes, sudden oak death, and more. Lots of photos. Local info.

Forest Pest Fact sheets - by Oregon Department of Forestry. Fact sheets for the pestiest pests. Photos to aid in diagnosis.

On-line catalog of western forest insects and diseases - links to many excellent fact sheets

Overview of Common Pine Problems

From the article "ALL THOSE DEAD TREES" in the Spring 2003 Applegator
By Ellen Michaels Goheen and Don Goheen

Pine engraver beetles in the genus Ips are associated with much of the top-kill of large pines and the tree mortality currently being observed in smaller diameter ponderosa pines. They are also killing entire large trees by themselves in some cases. These beetles most commonly infest stressed or wounded trees and down material, particularly of smaller diameters. Any activity of event that stresses trees or generates abundant amounts of slash is likely to lead to elevated engraver beetle populations. Slash produced from stand thinning activities between January and July is particularly conducive habitat for engravers, especially if the material is piled and not allowed to dry before beetle flights take place in the spring (usually starting in April or May). In a year of "normal" precipitation in southwest Oregon, pine engravers are generally confined to downed or severely stressed hosts and do not kill healthy trees.

Western pine beetle (Dendroctonus brevicomis) and mountain pine beetle (D. ponderosae) are responsible for much of the mortality we are seeing in larger ponderosa pines. Working singly, in combination with each other, and even joined by pine engraver beetles, adult pine beetles are attracted to stressed trees, and their larvae girdle trees by feeding in the phloem. Adults also introduce blue-stain fungi that grow in the tree's water transport system, plugging it physically, and hastening tree death. Adult pine beetles begin to fly in early summer (late June or July). It usually takes about a year for infested trees to die, and unfortunately, by the time most people notice the change in color of pine foliage from green to red, the new adults are already on their way to other trees. Risk of attack by western and mountain pine beetle can be reduced by keeping trees vigorous, by avoiding injury and abrupt changes to watering regimes, by removing competing vegetation from their root zones, and by keeping pines well spaced.

Overview of Common Douglas-fir Problems

From the article "ALL THOSE DEAD TREES" in the Spring 2003 Applegator
By Ellen Michaels Goheen and Don Goheen

Douglas-firs usually do not tolerate extreme drought conditions well, and the effects of the exceptionally low moisture in 2001 to 2002 are most visible in this species. Crowns are thin, tops and branches have died outright because the roots they were associated with were not able to obtain water, large trees have died. Insects and canker fungi have colonized weakened portions of trees, girdling branches and stems.

The most common insects in the drought stressed or dead Douglas-fir include: a) Douglas-fir twig weevils (Cylindrocopturnus furnissi) and other twig beetles that cause death of twigs and small branches, b) Douglas-fir engraver beetles (Scolytus unispinosus) that kill patches of cambium on the stem; this may cause branch or top kill, c) roundheaded wood borers that infest the branch collar area and main bole, d) flatheaded wood borers (Buprestids), particularly the flatheaded fir borer (Melanophila drummondi) that infests the entire tree, the top, or individual branches and has caused a substantial part of the large tree mortality observed recently, and e) Douglas-fir beetles (Dendroctonus pseudotsugae) that can kill large diameter (8" diameter or greater) trees. Flatheaded fir borer infestations often involve groups of trees in pockets that may expand from year to year when conditions are right for the insect. Trees infested by flatheaded fir borers often exhibit extensive evidence of woodpecker feeding. Adults fly from May to September. Stocking control and other vigor-enhancing treatments in host stands on high-risk sites may be worthwhile for reducing impacts by the flatheaded fir borer. Douglas-fir beetles have an earlier fight schedule; the adults emerge and find new host material as early as April at lower elevations or after mild winters. Douglas-fir beetles prefer weakened or recently downed trees. Their impacts can be reduced by maintaining tree vigor and by reducing levels of Douglas-fir blowdown to fewer than four, ten inch or greater diameter Douglas fir trees per acre.

Several canker-causing fungi, including Diaporthe lokoyae and Phomo spp., can infect and kill stems and branches of drought-stressed Douglas-firs. These fungi are weak pathogens that cause few if any impacts on vigorous trees. Canker disease occurrence usually increases after drier than normal weather and subsides during periods of normal or above normal rainfall.

Overview of Common Incense Cedar Problems

From the article "ALL THOSE DEAD TREES" in the Spring 2003 Applegator
By Ellen Michaels Goheen and Don Goheen, with additions by Max Bennett

Scattered pockets of fading or recently killed incense cedar are evident locally in our area. Examination of the boles indicates some colonization by cedar bark beetles (Phleosinus spp.). However, flatheaded woodborers (Buprestids) are most frequently associated with dead or dying trees. Most flatheaded woodborers infest recently killed or very severely stressed trees. Therefore, they are commonly associated with trees damaged by fire, wind, flooding, or drought. Many flatheaded woodborer species infest logging residues as well. We believe that severe moisture stress is the main factor predisposing incense cedars to woodborer attack in our area this year.

In spring of many years, an orange colored, gelatinous substance (think marmalade) coats the underside of many incense cedar branches. This is caused by the incense cedar rust, a fungal disease. While dramatic in appearance, damage is seldom serious is usually confined to witches brooms and death of small sprays of foliage.

An unseasonal freeze in fall 2002 apparently contributed to stress and subsequent mortality visible in spring 2003 in many incense cedar in SW Oregon, particularly in the Illinois Valley and Merlin areas.

What's killing my madrone trees?
12-30-03

What's wrong with the madrone trees in our area? Many southern Oregon residents have been asking themselves this question lately.

Pacific madrone (locally known as laurel) is affected by a variety of fungal diseases. Symptoms range from leaf spotting to twig dieback to death of major branches or the entire tree. Compared to healthy, vigorous trees, stressed trees are more likely to be infected and the extent of damage will be greater. Common stress factors include overwatering, poor soil drainage, soil compaction, and backfilling over the existing soil surface. All these can lead to asphyxiation of the roots and a marked increase in tree stress.

Drought often plays a role
Drought is another major stress factor. Drought stress occurs when water loss inside a tree exceeds uptake long enough to cause damage or disturb the tree's physiology. The usual result is reduced growth and increased vulnerability to a host of insect and disease problems. Although madrone and oak are adapted to the summer drought of southern Oregon's Mediterranean climate, excessively low precipitation, especially during the growing season, may result in growth losses and stress. That appears to be the case in 2001-03, as rainfall was below normal during this period. In addition, the cumulative stress of a decade of drought from the mid-80s through mid 90's may still be affecting trees.

Many stands in southwest Oregon are overstocked with trees and brush because fire has been excluded. Trees growing in these stands must compete for a limited quantity of soil moisture, which contributes to the moisture stress problem.

The influence of the flowering cycle
Madrones that flowered heavily in the year 2000 has remarkably stunted foliage in 2001. Apparently, the trees used a considerable amount of their energy reserves in flowering. Consequently, few reserves were available for growth of the next year's foliage.

Madrone leaf spot
More than half a dozen fungal organisms can cause leaf spots on madrone. Young leaves are infected by air-borne spores during wet weather, often in the spring. Trees growing in creek bottoms or valleys are most likely to be infected. Infection results in circular to irregular spots about 1/4 to 1/2 inch in diameter. A related disease produced irregularly shaped black tarlike spots on the undersides of leaves. These diseases may result in unsightly foliage but are seldom serious. They may lead to an increase in tree stress, however.

What can you do? Raking and destroying fallen leaves can help dampen the spread of spores and infection of new leaves.

Madrone root disease (Phytopthera cactorum)
This disease affects the roots and tree trunk. Cankers (areas of diseased tissue) are usually near the base of the tree but may occur further up the trunk. The infected bark is brown and the sapwood may also be discolored. Loss of foliage, and small, curled leaves are common symptoms. Infected trees often die, sometimes rapidly. Moist soil conditions favor the fungus; hence over-watered trees or trees growing in poorly drained soils are most susceptible.

The main way to avoid root disease problems to avoid overwatering. For yard trees, frequent waterings (every day or two) on flat or poorly drained ground are a recipe for trouble. While some individual madrone trees may do OK in these situations, the risk of developing root disease is much higher. Deep waterings every two weeks or so underneath the drip line but well away from the trunk may promote tree vigor during extended summer dry spells.

Madrone cankers (Natrassia and Botryosphaeria)
Branch dieback is caused by one or more canker diseases that have been increasingly evident recently. A canker disease is caused by a pathogen that kills localized patches of the tree's inner bark, resulting in the death of branches or whole trees. In madrone, entire trees or individual trunks die after exhibiting large black cankers that spiral down the stems. Alternatively, large numbers of branch tips turn yellow, foliage droops, and eventually the ends of may branches die, leaving the tree with little or no foliage. Symptoms develop rapidly, and even large trees can be severely impacted in just a couple of years. The diseases are apparently associated with temperature or moisture extremes that injure trees or warm, wet spring weather that favors infection. Trees growing at the edges of open areas, trees that receive summer irrigation, and trees growing in areas where the soil has been disturbed or compacted appear to be preferentially affected.

Cankers typically develop after a bark injury. This could be a mechanical wound or perhaps caused by sudden exposure of a branch or trunk to direct sunlight, as when a surrounding tree is removed. Vigorous trees can callus over the tissue killed by the canker.

What to do?
For landscape trees, deep, occasional watering once every two weeks near the drop-line and well away from the base of the tree should alleviate moisture stress during extreme drought conditions. Summer irrigation close to the tree trunk should be avoided because it may increase the tree's vulnerability to root disease.

The canker disease can be prevented by keeping trees free of damage and stress, and by avoiding soil disturbance, especially compaction. Once the canker disease is established in a tree, there's not much that can be done to control it. No fungicides are known to control the disease. However, if caught early, pruning and burning individual cankered branches seems worthwhile.

Sources:
Diseases of Pacific Madrone. Marianne Elliot. http://soilslab.cfr.washington.edu/madrone/ch07_el.pdf

Leaf spot of madrone. EM 2951, Washington State University Extension, April 1973.

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