Identifying Dead and Dying Conifers on Private Landin California

Don Owen

Forest Pest Management Specialist, 6105 Airport Road, Redding, CA 96022

The first section of this document will help propertyowners and others identify when a conifer is dead. Thesecond section discusses the more challenging task ofdetermining if a tree is dying. The definition of "dyingtrees" as stated in the California Forest Practice Rulesis used as a basis for this discussion. Although theconcepts discussed in this Tree Note are generallyapplicable to all dying conifers, the discussion does notspecifically address trees that are dead or dying fromfire-damage. A separate Tree Note on evaluatingfire-damaged trees is being prepared.

Dead TreesIdentifying a dead tree is, for the most part, relativelystraight forward, but there are situations where a livetree may appear to be dead. One of the first clear signsthat a conifer is dead is a uniform change in foliagecolor throughout the entire crown of the tree. Thefoliage of most conifers first turns yellow and laterlight brown and reddish/brown. Eventually the needlesbegin to fall, leaving behind bare branches. If someportion of the crown retains green needles, then part ofthe tree is still alive.

Some needle diseases and winter damage can causefoliage throughout the crown of a tree to change color.This change in color is typically noticed in the spring of the year, a time when these trees are often mistaken fordead trees. If you look closely at the foliage on thesetrees, it is usually possible to find some greenremaining - the bases of needles may be green or theremay be green needles interspersed among brownneedles (hence, the change in color is not uniformthroughout the crown). If the tree is dead, there will beno green left in the foliage. Living trees that sufferfrom needle disease or winter damage will produce new green needles when they break bud and renew growth in the spring. Hence, these trees will "green-up" duringthe growing season. Conversely, a tree that fails tobreak bud and produce new growth is dead.

Another condition that often erroneously leads to theconclusion that a tree is dead or dying is fall colorchange. Conifers typically retain needles for several

years, but each fall the oldest needles change color andare shed. The amount of foliage shed from year to yearcan vary considerably. When trees are under droughtstress, a large complement of older needles may changecolor, causing a large portion of crown to look yellow.The youngest needles, however, remain green - a suresign the tree is still alive. Heavy cone crops may alsocreate the appearance that the top of a tree is dying.

If there is doubt as to whether a tree is alive or dead, asimple test is to cut or chop into the inner bark orphloem. The phloem is the living portion of the barkimmediately adjacent to the wood. On a live conifer, the inner bark is cream-colored, often with a tinge of pink,and moist. Dead inner bark is brown and may appearmoist, dry, or resin-soaked. When the inner bark is dead around the entire circumference of the tree trunk, thetree is dead. It is possible to find trees that have aportion of the inner bark that is alive and a portion thatis dead. Such trees may have received a non-lethalinjury that killed only a portion of the bark, or they may have received a lethal injury and are still in the processof dying.

Dying TreesDetermining if a tree is dying can be considerably more difficult than determining if it is dead. While thefoliage of a dead tree will have changed coloruniformly throughout the crown, the foliage of a dyingtree will be green in whole or in part. The CaliforniaForest Practice Rules defines a dying tree as one thatmeets one or more of the following criteria:

• Fifty percent or more of the foliage-bearing crown is recentlydead (as indicated by a uniform change in color over that part ofthe crown). Dead tops that have no foliage do not count towardthis 50%.

• Successful bark beetle attacks with indications of dead cambiumand brood development are distributed around the circumferenceof the bole. The key concept here is that the beetles havesuccessfully girdled the tree. Evidence of beetle attack such as pitch tubes or pitch streamers, even if they extend around the tree, do not necessarily mean that the attacks have beensuccessful.

TREE NOTESCALIFORNIA DEPARTMENT OF FORESTRY AND FIRE PROTECTION

Arnold SchwarzeneggerGovernorState of California

Dale T. GeldertDirector

Mike ChrismanSecretary for ResourcesThe Resources Agency

NUMBER: 30 February 2005

• Seventy-five percent or more of the circumference of the lowerbole is girdled by wildlife. This principally relates to beardamage.

• The tree is designated by a Registered Professional Forester aslikely to die within one year. This is a professional judgmentbased on training and experience.

The 50% and 75% criteria are straight forward, butdetermining if a tree is dying from bark beetle attackrequires expertise and careful inspection of the tree. Agreen tree can be dead or dying from beetle attack, butsuch a determination needs to be made by a qualifiedevaluator. Different tree species are attacked bydifferent beetles, more than one species of beetle willattack an individual tree, and the different beetlespecies vary in their ability to kill trees. Similarly, theindicators of beetle attack will differ based on beetleand tree species.

Evaluating Bark Beetle and WoodBorer AttacksBeetle attacks on a healthy conifer typically producesome sort of resin (pitch) flow from the attack site. This may be in the form of pitch streamers, pitch tubes, orpitch granules. The pitch is the tree's defense againstthe invading beetles and a sign that the tree is fightingback. It takes large numbers of beetles to kill arelatively healthy tree and it is not uncommon to findtrees that have successfully repelled attack andsurvived. If all attacks produce resin flow, there is noreason to believe the tree is dying.

Trees under stress may not be able to adequately defend themselves. Beetle attack is a dynamic process and thetree's defenses may fail as more and more beetles attack the tree. Quite often the initial beetle attacks willproduce resin flow, while later attacks produce no resin. If a tree has pitch tubes or pitch streamers, it is a goodidea to look closer to see if other attacks are present. Ifthere are numerous attacks with little or no resin flow,the tree most likely is dying. The ultimate test involvescutting into the tree bole and inspecting the inner bark,preferably at a spot where dry boring dust hasaccumulated - indicating the site of an attack with noresin flow. If beetle larvae are present, the tree is mostlikely dying.

Following are some general guidelines for evaluatingbeetle attacks on various conifers species.

Incense-cedar

The beetles that attack incense-cedar are not considered tree-killers. Incense-cedars will be very close to deathby the time bark and wood boring beetles colonizethem. Generally, there will be little or no externalevidence of beetle attack. Cedar bark beetle attacks may produce small amounts of yellow boring dust, but it isdifficult to see. If there is some doubt as to whether anincense-cedar is dying, cutting into the bark and finding beetle larvae and/or brown inner bark will indicate it isalready dead or likely to die. Because incense-cedars

are not attacked by aggressive beetles, they tend to diemore slowly than other conifers.

True firs

The fir engraver beetle, Scolytus ventralis, is theprincipal beetle attacking red, white and grand firs. Itis a tree-killer, but not an especially aggressive one. Itcan cause top-kill and branch dieback but such damagedoes not always indicate that the tree is dying. Fir treesneed to be under drought or some other stress to bekilled by the fir engraver. Trees are attacked and killedduring the summer, but the foliage on some of thesetrees will not change color for many months. Manydead trees are not identified until the following spring.Attacks on relatively healthy trees will produce ribbonsof pitch running down the bole of the tree (pitchstreamers). Do not assume these trees are dying. At theend of a drought when beetle populations are still highbut tree resistance has improved, it is common to findmany trees with pitch streaming. Successful firengraver attacks are indicated by small piles ofyellow-brown boring dust in bark crevices. In the latesummer and fall, look for this boring dust as anindicator the tree is dead or dying. By winter, this dustmay be gone and you may need to look for otherindicators, such as foliage color changes andwoodpecker feeding. If you suspect a green tree is deador dying, cut into the bole and examine the inner barkto confirm this.

Douglas-fir

A number of beetles attack stressed Douglas-fir, butsignificant tree mortality due to these beetles isuncommon in California. The Douglas-fir beetle,Dendroctonus psuedotsugae, is most likely to kill treesafter its populations have built-up in windthrown timber or trees damaged by fire, defoliation or other factors.Orange-brown boring dust in bark crevices is a sign thetree has been attacked and is dying. Pitch streamingmay or may not be present on the upper half of the bole. The Douglas-fir engraver, Scolytus unispinosus, rarelykills trees, but occasionally it will kill young,drought-stressed Douglas-fir after beetle populationshave increased in logging slash. Look for boring dust in bark crevices.

Douglas-fir on drier sites are often attacked by theflatheaded fir borer, Melanophila drummondi. Branches and tops are often killed, but tree mortality is rare ormay take many years to occur. Attacks are marked bypitch streaming, although severely stressed trees mayshow little or no external evidence of attack.

Pines

The bark beetles that attack pines are among the mostaggressive. The western pine beetle, Dendroctonusbrevicomis, attacks ponderosa and Coulter pines; themountain pine beetle, Dendroctonus ponderosae,attacks many different pines, including sugar,ponderosa, Coulter, western white and lodgepole pines.A related beetle, the Jeffrey pine beetle, Dendroctonus

jeffreyi, attacks only Jeffrey pine. All native pines inCalifornia are also attacked by one or more species ofIps or engraver beetles, as well as the red turpentinebeetle, Dendroctonus valens. All of the precedingbeetles, except for the engraver beetles, produce pitchtubes when they attack a relatively healthy pine. Whenattacks produce dry boring dust instead of pitch tubes,this is an indicator the tree may be dying or is alreadydead.

When evaluating bark beetle attacks, it is useful todistinguish between current attacks and old attacks.Fresh pitch tubes are soft and somewhat shiny, whileold tubes are dull and hard. Old tubes on ponderosapine often have a yellowish color. Old pitch tubes on atree are generally of little concern because theyrepresent past attacks that failed.

Fresh attacks, in contrast, provide information on thetree's current condition. Individual attacks may produce a pitch tube, crumbly resinous material, and/or dryboring dust. If all the attacks are marked by either apitch tube or crumbly resinous material, it should not be assumed that the tree is dying. If little or no resin isbeing released by the tree, attacks will be marked bydry boring dust. Because a tree's condition can changeover time, it is typical to have some resinous attacksand some dry attacks on trees that are dying.

Although dry boring dust is a good indicator that a treeis dying, there are exceptions. Dry dust can be produced by red turpentine beetles as they bore through the thickouter bark at the base of the tree. They must borethrough the outer bark before reaching the phloem andin doing so can produce noticeable amounts of dry dust. Pitch is not released until the beetles reach thephloem/cambial region. Small amounts of dust may also be produced by relatively harmless caterpillars that bore into the bark of pines and other conifers.

Trees with large amounts of dry boring dust in barkcrevices and/or scattered around the base of the tree are likely dead or dying. Still it is a good idea to confirmthe tree's condition by cutting into the bark at a pointwhere dry dust has accumulated and looking for beetlelarvae.

Woodpecker feeding can also be an indicator of a dyingtree. If a tree is infested with beetles, woodpeckers may chip off bark to feed on beetle larvae and pupae. Smallamounts of woodpecker feeding often can be seen onperfectly healthy trees, but extensive feeding on a green tree most likely indicates the tree is infested withbeetles and is dead or dying. Most bark beetle broodswill be exiting the tree at about the time the foliage ischanging color, leaving behind small round exit holes in the bark.

Wood borers are sometimes the principal insectattacking the main trunk of pine trees, filling a nichethat is typically occupied by bark beetles. A goodexample of this is found on Jeffrey pines in San Diego

County and in the San Jacinto Mountains of RiversideCounty, where the Jeffrey pine beetle is absent. The red turpentine beetle may attack the base of these trees, butattacks higher on the bole are often made by theCalifornia flatheaded borer, Melanophila californica.No pitch tubes or boring dust are associated with borerattacks. On live trees, borer attacks are recognized bythe presence of pitch streaming down the bole of thetree. These attacks are difficult to interpret because theinsect does not need to kill the tree in order to survive.Larvae of M. californica may be pitched out and killedby the tree or they may survive in an incipient stage formany years beneath the bark.

Numerous pitch streamers may be an indicator the treeis under stress, but the pitch streamers do not mean thetree is dying. If numerous streamers are present, lookfor other indicators of the tree's condition - redturpentine beetle attacks, foliage color changes, andwoodpecker feeding. Most dead or dying pines willhave successful red turpentine beetle attacks. If yoususpect a green tree is dying, look for dry boring dustaround the base of the tree and cut into this area todetermine if beetle larvae are present.

Acknowledgements and DisclaimerThanks to staff of the California Department of Forestry and Fire Protection and the USDA Forest Service forreviewing this manuscript. These guidelines are for useon state and private lands, but are not intended to be asubstitute for the California Forest Practice Rules orany related policies of the California Department ofForestry and Fire Protection. National Forests and other Federal lands have separate guidelines for identifyingdead and dying trees.

All photographs were taken by the author. Digitalreproductions of many of the photographs wereprovided by Forestry Images and can be found on theirwebsite, www.forestryimages.org.

Gallery of Signs and Symptoms - Dead, Dying, and Living Conifers

Sugar Pine Needle Cast. One year's complement ofneedles was killed by thisneedle disease. Thesebranches were collected inthe spring before the flushof new growth. Thesubsequent flush of newfoliage was unaffected. Theappearance of dead needlesthroughout the crown of thetree was alarming, but thedisease had an insignificantimpact on tree health.

Sugar Pine Needle Cast. Thistree has suffered from needlecast several years in a row.While a single year ofinfection is typicallyinsignificant, chronic yearlyinfections can cause a declinein the tree's vigor. This livetree is at or near the pointwhere a RegisteredProfessional Forester mightjudge it as likely to die within one year.

Annosus Root Disease onGiant Sequoia. This livetree has green, yellow, andbrown needles. It isimportant to know thecause of such symptoms toappreciate the severity ofthe disease. Knowing thatthis tree is suffering fromannosus root disease, aRegistered ProfessionalForester would be justifiedin classifying it as a dyingtree.

Redbelt on PonderosaPine. The needles onthis tree received winter damage. Although thecrown of the tree has an overall brown cast,closer inspectionreveals that needlebases are green. The

damage is minor and the tree is neither dead nor dying.

A Sugar Pine killed byMountain Pine Beetle. Thistree is dead and the foliagehas just faded toyellow/green. As theneedles dry, they willfurther fade to yellow,straw, and red/brown. Thechange in color is uniformthroughout the crown, i.e.no green needles remain. Ifyou were to cut into thebark, you would find beetlelarvae and dead phloem.

Ponderosa Pineskilled by WesternPine Beetle. Thisphoto was takenSeptember 1. Thesetrees were green inearly July and hadfaded to yellow/green by early August.

Ponderosa Pines with recentlykilled tops. These tops weremost likely killed by Ips barkbeetles. According to the forestpractice rules, if fifty percent or more of the foliage-bearingcrown is recently dead, a tree is defined as dying. The tree in the upper left photo has less than50% top dieback and thereforewould not qualify as a dyingtree. The tree on the lower leftphoto has approximately 50%dieback and therefore wouldqualify. Survival of both ofthese trees depends greatly onwhether or not bark beetlessuccessfully attack theremainder of the bole. The bestway to predict survival of these trees is to look for evidence ofsuch attack.

Ponderosa Pine with an olddead top. This top has nofoliage and was not killedrecently. The presence ofsuch a top does not qualifythis as a dying tree.

Port-Orford-Cedar killedby Root Disease. Thisphoto illustrates thedifference in colorbetween living,cream-colored phloem and dead, brown phloem. Inthis case, the brownphloem is a symptom ofinfection by a rootpathogen. The tree isgirdled by the infectionand is dying. Bark beetleshave begun colonizing thearea above the infectedphloem.

Pitch Tubes of RedTurpentine and Western PineBeetles. Conifers defendthemselves from beetle attack by producing and releasingpitch or resin. On pines, pitch tubes will be produced aslong as the tree can defenditself. Pitch tubes alone donot indicate the tree is deador dying.

Pitch Streamerson White Fir.This is the boleof a tree cutduring a loggingoperation. Thepitch streamerswere presentbefore the treewas harvested.

Like pitch tubes, pitch streamers are a sign that the treeis defending itself from attack -- either by bark beetlesor wood borers. Pitch streamers alone do not indicatethe tree is dead or dying.

Boring Dust fromBark Beetle Attacks.When a conifer isincapable ofdefending itself from bark beetle attack,little or no resin willbe released. As thebeetles tunnel intothe bark, they will

expel a "dry" boring dustfrom their entrance holes.No pitch tubes or streamswill be produced. Dryboring dust is an indicatorthat the tree is dead ordying. Confirmation of thisis made by cutting into thebark and finding beetlelarvae.

Red Turpentine Beetle Larvae. Bark beetlelarvae are creamywhite, legless, small(up to about 3/8", butgenerally smaller) and have dark heads.

Woodpecker Feeding andWestern Pine Beetle Exit Holes on Ponderosa Pine.Woodpeckers will feed onbeetle larvae and pupae beneath the bark of dead and dyingtrees. Extensive woodpeckerfeeding on a green tree may bean indication the tree is dying.If there is some doubt about the status of the tree, cut into thebark and inspect the phloem.Most trees will have changedcolor by the time bark beetlebroods begin to exit throughthe bark.