SPRUCE-FIR FORESTS
A Summa r y of Pe rt inent Inf o r ma t io n fo r the
G re at Smoky Moun t a in s National Pa rk
Prepared a s part o f
The Up l a nd s Fiel d Res e arch L ab orat ory
Volunt eer— in-Pa rks
Int erp re tation of S cienc e Proj ec t
Funded the G reat Smoky Mount ains Natural His t ory As s oc iation
1 1 83 May . 9
TABL E OF CONTENTS
SIGNIFI CANCE OF THE BAL SAM WOOLLY ADELGID IN THE SOUTHERN APPALACHIANS
THE SOUTHERN APPALACHIAN SPRUCE-FIR FOREST Phys ic al D es crip t ion D is t ribution - Human Impact t o the Spruc e Fir Fores t s
THREATS TO THE SPRUCE— FIR FOREST Human D is turb anc es Ac id Ra in
HI STORY AND D I STRIBUTION OF THE BAL SAM WOOLLY ADELGID
BAL SAM WOOLLY ADELGID LIFE HI STORY Life Cycle Reproduct ion
BAL SAM WOOLLY ADELGID EFFECT ON FIR TREES Types o f At t acks Phys ic al Change s in Infe s t ed Trees Feed ing and Mic ros copic Change s Fac t ors Af fec t ing Ho s t Suit ab il ity
REGENERATION OF INFESTED STAND S
BAL SAM W' OOLLY ADELGID CONTROL METHOD S Manipulat ion o f Fras er Fir Communit ies and Es t abl is hment o f S e ed Orchards Biol ogic al Control Chemic al Cont rol
CONTROL AND POLI CY IN THE GREAT SMOKY MOUNTAINS NATIONAL PARK
REFERENCES CITED FIGURES
Dis t ribution of Ab ies s pp . and the bal sam wo ol ly adelgid in North Americ a
Spruce— f ir dis t ribut ion in the S outhern Appal achians
Dis t ribution of s pruce- f ir in the G reat Smoky Mount ains National Park
Schematic c ro s s s ec t ion of a Fras e r f ir s t em showing the princ ipal s t ruc tures and bal sam wo olly adelgid feeding s it e
Cl oseup of b als am wo ol ly adelgid feed ing s it e SIGNIFI CANCE OF THE BAL SAM WOOLLY ADELGID IN THE SOUTHERN APPALACHIANS
The b al s am woolly adelgid (Adelge s p i c e ae ) is an exo t ic ins ec t that
at t acks mo st s pec ies o f t rue f ir in North Ame rica . I t was
int roduc ed from Europ e at the turn of the century , and s inc e then it
has bec ome e st abl ished by a s ep arate introduct ion in New England and
e ast e rn Canada , in the S outhe rn App al achi ans , and in the Pacif ic
Northwes t . In the S outhern Appalachians , it has caused ext ensive
mort al ity among Frase r fi r ( Ab ies frase ri ) .
s h as Fras er Fi r i the only f ir endemic t o this reg ion , and damage
been such that the very exis t enc e of this sp ec ies i s threat ened . It
rep res ents an i rreplac eab le gene tic entity and is an int egral part
v- of one of the more unique eco syst ems found in this r e g io n the
- S outhern Appalachian s pruce f ir fores t . Thes e fo res t s are famous
fo r thei r disj unc t nature and end emism of pl ant sp ec ies cont ained in
them . The dis appearanc e of Fras e r f ir would f o r e s e e ab ly affec t the
whol e sys t em in unknown way s .
In addit ion t o b e ing an invaluabl e s cientif ic res ourc e , this fo res t
provide s recreat ion opportunit ies and enj oyment fo r mil l ions of
v is it ors every ye ar , as wel l as ec onomic revenue t o al l tho s e in the
are a who provide good s and se rvic es for them .
The presently avail ab le b al s am wo ol ly adel gid ( fo rme rly c al led the
bal sam wo olly aphid ) cont rol me thod s are no t suit abl e fo r large
i s s cale appl ication , and it c onc eivabl e that the c urrent trend of
des t ruc t ion c ould cont inue t o the point of to t al ext inct ion of
Fras e r fir . In the following page s , effo rt has be en made t o exp res s the
c ompl exity of this is sue in simpl e t erms , ye t without omitt ing any
de tails rel evant t o the unde rs t anding of the whol e is sue .
SOUTHERN APPALACHIAN SPRUCE-FIR FOREST
Phys ic al D es cript ion
The cl imat e of the S outhern Appalachian s pruce— f ir fo res t is
u charact e riz ed by high winds , co ol s mme rs and c ol d wint ers .
Prec ipit ation and humidity are high throughout the ye ar . The
g rowing se as on ( the time in a year be tween the l as t fros t and the
firs t one ) is short and the s oil s are thin and ac idic (Mc cracken e t
a l . 1 96 2 ; St ephens Al l thes e fact ors c omb ine t o al l ow only
— the presenc e of c ert ain species well suit ed fo r this environment .
The Southern Appalachian sp ruc e— fi r forest s are dominat ed by red
spruc e ( Pic e a rub ens ) and Fras e r f ir . As soc iat ed canopy s pec ies
include yellow b i rch (Betula lut ea) , f ire cherry ( Prunus
- pensylvanic a) , and Ame rican mount ain ash ( Sorbus americ ana) . Frase r
f ir is the only t rue f ir oc curring in this region and it is al s o
limit ed t o this region alone .
In the S outhern Appal achians , Fras e r f ir density increas es with
el evat ion s o that mos t mount ain top s ab ove 62 0 0 feet in this region
are c overed exclusively by Fras e r f ir (Whit t ake r In mixed
s t ands at ab out 5 80 0 , Frase r f i r s eedl ings are ab out f ive times more
numerous than red spruce s eedlings ( Oo st ing and B il ling s There are als o other dif fe renc e s be twe en the two s pec ies . Red
sp ruc e att ains a great e r s iz e (maximum height 1 20 fee t , maximum
diamet er 40 inches vs . maximum height of Fras e r f ir 7 5 fee t , maximum
diamete r 3 0 inches ) . Red sp ruc e grow sl owe r but live l onge r (up t o
40 0 years a s oppo sed t o Fras e r f ir has a higher s e edl ing— t o
- mature tre e rat io and is a very prolif ic s eed produce r . Both red
spruc e and Fras er f ir are quit e shade t ol erant and res pond wel l t o
releas e . The roo t s o f Frase r fi r are deepe r and grow more rapidly ,
enabl ing it t o survive in s oils where the uppe r inch or s o has b e en
dried by sun and wind . Cons equently , Frase r f i r is imp ort ant as a
— p ionee r spec ies rep roducing fast and oc cupying openings .
S ome typical pl ant s of b ore al fores ts throughout North America find
their s outhern l imit in the S outhern Appalachian mount ains ( Pe t er
Whit e , pe rs onal c ommunicat ion)
Prunus pensylvanic a Fi re cherry
So rbus americ ana Americ an mount ain- ash
Ac e r s pic atum Mount ain mapl e
Sambucus pubens Red-berried elde r
Viburnum alnifol ium Hobbl eb ush
Rubus c anadens is Smoo th bl ackbe rry
Circ ae a alpina Smalle r enchant er ' s-night shad e
Cl in t o na b oreal is Bluebe ad l ily
Oxal is mont ana Wood s orrel l
Othe r specie s are f ound in S p ruce- f ir forest s in northe rn regions
and in the S outhern Appalachians but are mis s ing in the int ermediat e s n regions . Oo ti g and B illings ( 1 95 1 ) rep ort ed an unusual ly high proport ion of sp ec ies c ommon t o bo th sp ruc e-f ir fores t s of the
S outhern Appalachians and of the Whit e Mount ains in New Hamp shire .
1 96 4 3 6 7 8 L ikewis e , Hof fman ( ) report ed that famil ies of plant s ,
genera , and 1 09 species and varieties we re common t o the bo real
A forest s of Canada , l aska . and the Gre at Smoky Mount ains (Bone r
1 97 9 ; page
Among the mo st ext reme of these disj unct s are ( Pet er Whit e , p ers onal c ommunic at ion)
Gentiana l ine aris Linear—le aved gent ian
Betula co rdifoli a He art — leaved pape r b irch
L onic e ra canadensis Canadian honeysuckle
Mil ium ef fusum Wil d mil let
Thelyp t eris phegopt e ris Northern be ech fe rn
There are a f ew spec ies which are endemic t o the Southern
Appalachians ( Pe t er Whit e , pers onal c ommunication)
Ab ies fraseri Frase r f ir
Rhododendron c a t awb i e ns e Catawb a rhododend ron
D iervil la s es silifolia S es sil e-leaved bush- honeysuckle
Chel one lyonii Pink turtl ehead
S ol idago gl omerat a Skunk gol denrod
There are three plant species l imit ed t o the s pruce— f ir z one in the
Great Smoky Mount ains Nat ional Park alone . Thes e are
' Cac al ia r u g e l i a Rug e l s ragwo rt
Glyceria nub igena Smoky Mount ain mannagras s
' - Calamagros tis c a in ii Cain s reed b ent gras s To il lus t rat e the ge og raphical dive rs ity of pl ant s and the great numbe r of northern s pec ies represent ed in the S outhe rn Appal achians
% % v the c oncept o f a t rip t o Lab rador has aris en . Tra el ing from the lowl ands of the S outhern Appalachians t o the mount ain t 0 p s is the
s ame , climatic ally and flo ris tic ally , as t aking a t rip 1 0 0 0 mil e s
north , al l the way t o Lab rador .
Dis t ribut ion
The s pruce- f ir fo res t s or b oreal fo res t s a re wid ely dis t ribut ed throughout North Americ a ( See Figure In the far north it i s the f irs t type of fo res t enc ount ered as one moves s outh from the
% % tre el es s tund ra . ( The t erm b oreal me ans of o r pert aining t o the north ( Random House In the mount ains of New Engl and
it is found at incre as ing al t itudes , where it is the l as t fores t
typ e found p rio r t o the t re e line . In the S outhern Appal achians it
is found ab ove el evat ions of fee t , and this region represent s
the s outhernmo s t l imit of it s range .
The S outhe rn Appalachian spruc e- fir forest s have much in c ommon with the Northern Appalachian fo res t s t o which they we re ge og raphically connect ed during the Pl eis t ocene e ra ( Oo s t ing and B ill ings
During that e ra (when the cl imat e w a s c ool e r than it is t od ay )
- spruc e fir fores t s advanc ed t o l owe r el evat ions and , henc e , c overed
o a greate r a rea . Disj unct ion probably t o k plac e aft e r the cl imat e
— warmed and the s p ruc e fir fores t s migrat ed t o highe r el evat ions . % avln rm: ( “ m u s sm o mo uou s r . l
Dis tr ibu s s w o ll ad e l i d i n No r th Ame r i ca . tions o f Ab ie p p . and the ba l s a m o y g
( f r om G r e e nb a nk 19 7 0 ) During the xe ro thermic pe riod following the Wis c onsin glac iation ( or hyp s ithe r mal ab out 5 0 0 0 ye ars ago when the climat e was warme r than it is t oday) the spruce-f ir rec ed ed t o highe r alt itude s and p o ssib ly
dis appeared from s ome peaks altoge the r . As the climat e co ol ed , these peaks lacked the s eed s ourc e es sential t o es t ab lish new populat ions of sp ruc e-f ir (Whit t ake r This may ac c ount for the fac t that not all el evat ions in the S outhern Appalachians ab ove
fee t have Frase r f i r .
Human Impac t t o the Spruce-Fi r Fo rest s
- His t oric ally , man has been the great es t threat t o the sp ruc e f ir
fores ts in the Southern Appalachians . Befo re the arrival of the
whit e se t tle rs , thes e fores t s and the red S p ruc e forest s of Wes t
Virginia and Pennsylvania c overed around hec t ares
acres ) . Clearing fo r agriculture and mino r l ogging l e ft
hec t ares ac res ) by 1 86 0 . Sub s equent exploit ation further reduc ed the S p ruc e— fir t o ab out hect ares acres )
(Hopkins 1 8 9 9 as s een in SAR RMC
The demis e of this fores t during the las t hundred ye ars ha s c ome
a s mainly a result of c arel es s logging ac tivit ies . During the
2 h beginning of the 0 t century , sp ruce and f i r we re ext ens ively
harve st ed fo r lumb e r and pulp , le aving only a few inac ce s sible fores t s at highe r el evat ions unt ouched (mo s t of which are l ocat ed
within the Great Smoky Mount ains National Park ) . Slash woul d oft en
a s cat ch on f ire , dest roying the remaining veget at ion as wel l se ed s
ac cumul at ed on the ground . These f ires we re oft en fol lowed by 8
ext ensive ero sion . Whereas unburned logged s t and s had a go od chanc e
of regenerat ing and achieving a sp ec ies c ompo s ition similar t o the
o riginal one , burnt areas devel oped int o heath and s crub wo od with
lit tl e o r no fir — a condit ion which may t ake from 2 0 0 t o 1 0 0 0 ye ars
for rec overy t o return t o a c omp osit ion simil ar t o the
original one ) ( S aunde rs
Presently mo st of the remaining spruce- f ir areas are unde r federal
or s tat e ownership ( S ee Figure 2 fo r the dis tribut ion of sp ruce— f i r
in the S outhern Appalachians ) . More than hal f of this area
hect ares o r acres ) is locat ed within the Gre at Smoky
Mount ains National Pa rk ( S ee Figure 3 f or dis tribut ion of spruce- f ir
in the Gre at Smoky Mount ains Nat ional Park) . The res t of the are a
is divided be tween the Black Mount ains in North Carol ina with
hectares acres ) ; the B al sam and the Plo t t Bal sam Mount ains of
the Pis gah National Fores t and the Blue Ridge Parkway ; Roan Mount ain
( shared be tween the Pisgah and Che rokee Nat ional Forest s and privat e
ownership ) ; Mount Roge rs Rec reation Area in Vi rginia ; and
Grandfathe r Mount ain , unde r privat e ownership .
3 E — . THR ATS TO THE SPRUCE FIR FOREST
There are s everal threats t o the spruce f ir fores t s in addit ion t o
the b al s am wo olly adelgid .
Human Dis turb anc es
B ec ause of the fact that mo s t of the remaining s pruce— f ir forest s
are us ed fo r recre at ion purpo s es , a range of human dis turb ances such
Acid Rain
The ext ent o f damage caus ed by ac id precipit ation in the S outhern
— Appalachian spruc e fir forest s have not been det ermined . Rainf al l
in the s pruc e- f ir z one is ab out twic e as much as that at low
- elevat ions . In ad dit ion t o rainf al l , sp ruc e f ir forest s rec eive
ab out an addit ional 5 0% mois ture input from cloud and fog
condens at ion (D ouglas Holland , pe rs onal c ommunicat ion) . In s ome
c as es , fog and cl oud mois ture wil l c ont ain four times as many
dis s olved hydrogen ions ( a me asure of ac idity) as the to t al rainf all
- — at low elevations . This is bec ause of the greater surfac e t o volume
rat io of fog part ic iples , which enabl es them t o t ake up more sulphur
( NO ) ( dioxide and nit rous oxide X particl es the c auses of ac id
rain) (D ouglas Holl and , pe rs onal c ommunicat ion) . I t f oll ows , then ,
that spruce-f ir fores t s may rec eive as much as 1 0 times the amount
a s of ac id precipit at ion ( or , more sp ecif ical ly , hydrogen ion input )
l ower el evations ( 2x for rain 2 x 4x fo r ac id in fog and cl ouds ) .
Research in the Whit e Mount ains o f Ve rmont ( S ic c ama e t a l . 1 9 8 2 ) has
shown a 5 0 perc ent reduct ion in red spruce b as al area during the
period from 1 96 4 t o 1 97 9 . Many of the remaining trees in these
s t ands show s igns o f s t res s and are in poor c ondit ion . The autho rs
dis cus s the po s s ib l e role o f ac id precipit at ion as well as o the r
fac t ors in this dec l ine but s t op short of identifying a causal
agent .
Many ques tions remain unanswe red c oncerning the ef fec t acid
prec ip it at ion has on the t ot al S outhe rn Appal achian spruce-f ir s v sys t em , such a : What ef fec t do es ac id prec ipit ation ha e on an
already ac idic s oil with ve ry l it tl e buf fering capac ity , and what
are the e ffec t s o f the dec re ased p H?
In the Gre at Smoky Mount ains Nat ional Park an acid rain monit oring
program has b een going on s ince 1 97 8 , and res e arch on the spec i fic
eff ect s of ac id precipit at ion at highe r el evat ions is unde r way .
HI STORY AND D I STRIBUTION OF THE BAL SAM WOOLLY ADELGID
The b al sam wo olly adel gid was f irs t dis c overed in Maine in 1 90 8
K sk T ( o tin y , h e prob ab le me ans of introduct ion s eems t o have
been impo rt ed nursery s t ock from Europe . In 1 91 6 , it was dis c ove red
on Mount Monadnock in New Hamp shire and , in 1 9 2 9 , it was repo rt ed in
i s Nova S c otia (Bal ch , In the Northe as t , it pre sently
dis tribut ed throughout s outhern Maine , New Hamp shire , Ve rmont and
northwest ern Mas s achuset t s . In Canada , it has b ec ome est abl ished
throughout Nova S c otia , Princ e Edward Is land and s outhern New
B runswick ( S cho ol ey and B ry ant . It s ho s t in the Northe as t is
b al s am f ir , and damage has oc cas ionally be en s eve re (Bal ch
A s eparat e int roduct ion b rought the adel gid t o the west ern Unit ed
A S t at es where it was dis c ove red in 1 9 28 ( nnand , The bal s am
i s W wo olly adel gid now present in Oregon , ashingt on , and s outhe rn
A B ritish Columb ia . Throughout North me rica , the b als am wo ol ly
adelgid ha s not ext ended more than 1 0 0 mile s from each c oas t exc ep t
for the inf est ations in the S outhe rn Appalachians (Greenb ank , The b als am wo ol ly adelgid was dis cove red in 1 957 on Mount Mitchel l ,
the highes t peak in the Southern Appalachians ( Spe e rs ,
Judging f rom the damage present at the t ime , introduct ion of the
ins ec t mus t have oc curred around the lat e 1 93 0 s . How the ins ec t was
introduced is not known . A po s sib ility is the ext ensive reforest ation p rograms which included European s ilve r f i r that were
taking plac e on Mount Mit chel l at that t ime ( C . Eagar , pers onal
c ommunicat ion) . In 1 96 2 , the b al sam wo olly adelgid w a s dis c ove red
on Roan Mount ain t o the north of Mount Mitchell . In 1 9 6 3 , it was
dis c ove red on Mount St erl ing , the e ast ernmo s t pe ak in the Great
Smoky Mount ains National Park , and it was no t until 1 97 2 that
Clin mans e t al adel gid s were dis c overed on g Dome (Hay . the
' limit o f the Fras er f ir s ext ension t o the wes t . By that t ime it was thought that the b alsam woolly adel gid had c oloniz ed the entire
- S outhern Appal achian spruc e f ir z one t o s ome ext ent , except the
st ands on Mount Rogers in Virginia . Monit oring ef fort s by the U . S .
Fores t S ervic e in 1 97 9 de t ec t ed two smal l inf es t ations on Mount
Rogers . Subs equent work reveal ed that the adel gid had been present
2 s inc e 1 96 , however , mo rtal ity and damage t o Fras e r f ir on Mount
Rogers is cons iderably l es s than in o the r S outhern Appalachian areas
(J ohns t on The re as ons for this apparent t oleranc e are s till
not fully underst ood . WOOLLY ADELGID LIFE HI STORY
The bals am wo ol ly adelgid b el ong s t o the insec t orde r Homopt era ,
- Ad l n family Phyll oxeridae and sub family e gi a e .
The Ad e lginae are charac t eriz ed by a very c ompl ex l ife cycl e
involving alt e rnat ion be tween s exual and as exual reproduct ion and
als o b e tween ho st s (Bal ch In Europe Adel ges pi c e a e is a
rel atively harml es s pes t on it s ho s t , Europe an s ilve r f i r (Ab ies
alb a) . In it s new env ironment in Ame ric a howeve r , it found
favo rab le c onditions and caused ext ensive damage t o it s ho st ,
part icularly in the Southern Appalachians . I t ha s no natural
predat ors o r paras it es and is very res is t ant t o ext reme
environment al c ondit ions . I t is cap abl e of surviving eight days
without feeding and has a t remend ous rep roduct ive po t enti al .
The lethal l ow t emperature for the adel gid is -3 5 ° C fo r the
0 ° overwint e ring generat ion and C for all o ther s t age s . High
amb ient t emperature s will no t have an adve rs e ef fec t on the adel gid ;
on the c ontrary , they may inc reas e the rat e of devel opment
(Greenb ank
Des ic cation may oc cur as a resul t of high b a rk t emperatures and low
u h midity . Prot ec t ion agains t des ic cat ion i s af fo rded by the wo ol
( ac tually a waxy s ec retion) and the ins ec t s hab it o f se t tl ing
predominantly unde r branche s , in cracks and in lent ic el s ( small
opening on the b ark o f Fras er f ir) . Rain may mat the wo ol and
sub s equently le ad t o des ic cat ion . It may als o wash away the adelgid s (B al ch In summary , cl imatic fact ors have very
l it tl e effec t in reduc ing the to t al populat ion ; in fac t , the mild c onditions p reval ent in the S outhern Appal achians have a b enef icial
inf luence on the adel gid .
Population c ontrol is exe rt ed mainly by the carrying capacity of the
ho s t . The numbe r of adelgid will incre as e as long as the ho s t is abl e t o p rovide food fo r al l individual s (B al ch Onc e the
tre e is unab le t o do this , populat ions will st art decl ining and v eventually die out . By that time , howeve r , the t ree will ha e
incurred such damage that it will usual ly die .
D ispers al is pas s ive , depending predominantly on wind current s , and
oc curs only during the egg and crawle r st age s . Surfac e winds c an
c arry adelgid s 3 0 0 feet , and ve rtic al air current s c oul d c onceivably
trans port adelgid s for s eve ral miles (Bal ch
Life Cycl e
The l if e cycl e of the b al s am wo ol ly adelgid c onsis t s of an egg
st age , thre e larval inst ars , and the adul t . The foll owing des crip t ion of the b als am wo olly adelgid ' s life cycle is based on
a ob servat ions by B al ch ( 1 95 2 ) as summariz ed by Hay e t l .
Eggs laid by the s t ationary adul t are at tached t o the
hos t bark by a s ilken thread . Initially l ight amber
c olored , the eggs bec ome orange b rown a s the emb ryo
develop s . Aft e r ab out 1 2 days young larvae eme rge ,
leaving the empty shell b ehind . This is the f irs t
ins tar , and the only st age c ap ab le of movement . The se
mobile l arvae or c rawle rs as they are als o known , are
l ight purpl e with a flat t ened oval b ody be twe en . 3 5 4 mill ime t er and . 7 mill ime t er l ong . They have three pairs of ful ly funct ional legs and are cap able of c rawling up t o 3 0 me t ers in s e arch of a suit able
feeding s it e . ( I t is unlikely that they would crawl
from one t ree t o another . ) Af t e r inse rting it s s tyle t ( a slende r thread— like mouth part us ed f or feeding )
int o the hos t b a rk , the insec t turns dark purple black with a fringe of whit e waxy thread s and the l egs and
ant ennae b egin t o atrophy . The ins ect s remain st at ionary during the f ol l owing thre e larval molt s A
dormant period of variable l ength will fol low . Th i s i s the s t age that the ins ec t s ove r w int e r and are known as ns hi emo s is t e , whil e the summer gene ration are known as vo s is t ens hiemo s is t e n s a e s ti . The b egins t o feed when s a a e s t vo s i s t e ns the p ris es in the s pring , whil e the i
are dormant fo r thre e t o eight weeks .
The s ec ond inst ar develops aft er the f irs t mol t . I t
has a longe r mil limet e r t o . 5 5 mil l imet er) and
b roade r b ody than the f irs t inst ar , with l ong , curl ing ,
waxy thread s .
f A t er a s ec ond mol t , the thi rd inst ar develop s . This
one is similar to the s ec ond , except that it i s . 6 0
mill imet e r t o . 86 mil lime t er l ong . The adul t s devel op
aft e r the third molt and are . 7 0 mil limet e r t o
mill ime t e r l ong , hemispheric ally shaped and cove red % % with l ong , curl ing , waxy thre ad s of wo ol .
The numbe r of generations in a ye ar depends mainly on the cl imat e .
The warmer the climat e , the more generat ions wil l b e produc ed . In
marit ime Canada and New England , two gene rations a re the rule .
(Bal ch , Due t o the wide range of el evat ions in the Pacif ic
Northwest , the numb e r of generations range from two at high
alt itudes , three in the int e rmediat e al t itude s , t o four at l owe r
t l alt itudes where climatic c ondit ions are opt ional (Mit chel l , e a .
i s In the S outhern Appal achians , there a simil ar variation in the
u numbe r of generat ions but two are the gene ral r l e . Reproduct ion
The bal s am woolly adelgid reproduce s by parthogenes is ; that is ,
without mat ing or fert iliz at ion . The entire populat ion cons ist s of
femal es , all capabl e of producing eg gs . Ovip osit ion b egins three
days aft e r the final mol t and may cont inue fo r up t o f ive weeks .
The adul t will die s oon aft e r c ompleting this proc es s . An adul t of
the hiemo s i s t ens ( overwint ering) generat ion wil l produc e around 1 0 0
eggs ( al though figures of more than 20 0 have be en rec orded ) . The
adul t of the les s f ecund a e s t ivo s is t ens generat ion gene ral ly lays
around 5 0 eggs (B al ch Using two generations pe r ye ar and a
survival rat e of 6 01 , 1 80 0 adelgids can be produc ed from a s ingle
individual in one ye ar .
BAL SAM WOOLLY ADELGID EFFECT ON FIR TREES
Types of At t acks
Bals am woolly adelgid at t acks can be clas sif ied in two cat ego ries ;
c rown infest at ions and st em infest at ions (Balch , The typ e of
inf est ation will depend mainly on the host s pec ies . Bals am f ir , fo r
example , usually suf fers from the c rown infest at ion whil e Frase r f ir
suf fers p redominantly s t em at t acks ; however , bo th species can suf fe r
eithe r kind of at t ack . S t em infest at ions tend t o b e more s eve re
than c rown infes t ations bec ause they can af fect the entire t ree ;
c rown infes t ations af fec t part s immediat e t o the at t ack s it e , and
the t ree may rec over even aft e r a heavy inf es t ati on ( Balch ,
20
t o the res t o f the t re e . Lack of wat er in the s oil will aggravat e
this condit ion and therefore c aus e fas t er de ath .
Feeding and Mic ro s copic Chang e s
The fol lowing ac c ount of b als am wo ol ly ad el gid feed ing ac t iv ity is b as ed mainly on des cript ions by Bal ch Othe r s ources are
indic at ed when appropriat e .
Af t e r the adelgid has found a suit ab le feeding s it e , the newly hat ched larvae ins ert s it s s tyle t int erc ellularly through the
p eriderm int o the c ort ic al parenchyma ( s ee Figure Fe ed ing does
not st art until the ins ec t ha s gone through a res t ing s t age .
Swell ing o f the ins ec t b ody and a cle ar drop of honeydew at the anus
indicat es that feeding has s t art ed . Feed ing only t akes plac e in the
' parenchyma c ell s . A subs t ance within the insec t s s aliva will
dif fus e int o the cells surround ing the s tylet . This c aus es thes e
cell s t o increas e t remendously in s iz e ( around 6 t o 7 t ime s the
normal s iz e ) . There is als o a thickening of the c ell wall and an
enl argement of the nucleus ( s e e Figure
The s al ivary subs t anc es s ecret ed by the adelgid during feeding even
affec t s the dis t ant xylem . Cell d iv is ion is s t imul at ed in the
camb ium and there i s a produc t ion of tracheid s with thickened ,
r irregul arly shap ed c ell wall s and da k hard b rit tl e cellulo se . This
% % % % i s it s known as a ro tholz or redwood bec aus e of reddish c ol or ,
and it cl o sely resemble s c omp res sion wo od ( the wo od on the unde rs ide
of a b ranch that is c ompres s ed by the weight of that b ranch) . The
Bal sam Woo ll y Adelgid
Abnor ma l Par enc hyma Ce lh
F e 5 : C s e u b a am w a f e e S e i n s e t igur lo p of l s ool l y d e lg id e di ng s i t . ty l t ( S ) s i r e d e h ma i n t e r c e l l u l a rl y through the c ork a nd cork c a mb i um in to the c or t ic a l p a r nc y . Abn o ma c e s e ve a n t l o f s t r l ll d lo p ro u d p tyl e . 23
memb ranes o f the b o rde red pit pairs in the xylem , the mic ro s copic
opening s through which wat e r and nutrient s pas s , will b ec ome encrus t ed and the pas sage of fluid s will be s eve rely impeded
( Pu r it ch and Johns on
The exac t ac t ive c onstituents o f the sal iva have no t be en
i s det ermined . Indoleacet ic ac id ( IAA) , a growth ho rmone , susp ect ed t o b e one o f the main c omp ounds involved in al t e ring the ho s t ' s
c ellular s t ruc ture ( Chris Eagar , pe rs onal c ommunicat ion) . I t is thought that IAA may fac il it ate the f low of nut rient s t owards the
feed ing s it e , thereby providing more nourishment fo r the adel g id and
causing adj ac ent cells t o grow . Seve ral fac t s support this the ory
Diamet e r g rowth increas es at the time of infest at ion ; adelg ids
— prefe r t o s e t tl e in g roup s on the s t em (Hay e t a l . , 1 97 8 ) the c omb ined ac t ion of many individual s would be more ef fec tive than
that of a s ingl e one . Al s o , ad el gid survival may inc reas e as the bark is changed by fe eding (Bal ch
De ath of Fras e r f ir apparently resul t s f rom the imp ediment of fl ow
through the b o rdered p it pairs of the xyl em ves s el s ( Chris Eage r ,
m p ers onal c om unic ation) . The rat e o f mo rt al ity inc re as es during
drought c ondit ions . Infes t ed tre e s s eem al s o more sus c ep tibl e t o
Armil laria ro o t ro t (Hudak and Well s , This fungus des t roys the camb ium and phloem of the root s and ro o t c ol lar and is an
addit ional c ause of mo rt al ity . Damaged and weakened t re es a re al s o
W more vulne rabl e t o indthrow and t op breakage . F edde ( 1 97 3 ) obs erved that the cumul ative s t res s f rom a b al sam wo olly ad el gid 2 4
at t ack als o reduces the s eed c rop but , given the short time it take s
fo r adelgids t o kil l a tree , this shoul d have l it tl e ef fect on the
t o tal Fras e r f ir population dynamic s .
- Where as in normal sp ruc e f ir s t ands the thre at of fire is minimal , the ac cumul ation of de ad t rees in an infes t ed s t and creates l arge
amount s o f fuel . A fire would no t only des t roy surviving trees but
it woul d als o reduce the p ot ential fo r regeneration . The o rganic
mat t e r would burn , exp o s ing the mine ral s oil and providing a se edbed
a sh more suitab le f or yel low b i rch , f ire cherry , and mount ain , and
l es s suit abl e for Frase r f i r . Al s o , ac cumulat ed Frase r seeds in the s oil which normally remain viable f or around f ive ye ars would b e
des troyed .
Fac t ors Af fec t ing Hos t Suit ab il ity
No t all Frase r fi r are equally af fect ed by the b als am wo ol ly
adelgid . S imilarly , infes t ations in dif fe rent s t ands do not always
fol l ow the same pat t e rns .
Y oung vigorous t rees le s s than 2 0 ye ars of age rarely have large
adel gid populat ions , and tree mort ality at this st age is no t
frequent ( Chris Eage r , pe rs onal c ommunic ati on) . It appe ars that
adelgids require modif icat ions of the tight , smoo th gray bark
charac t e ris tic of young vigorously growing Fras e r f ir t rees . These
modif icat ions are S pl itt ing of the bark and f ormat ion of lent ic el s , a proc es s that generally oc curs aft e r the t ree is 1 5 t o 20 ye ars
old . S tres s from c ompe tit ion will c aus e thes e modi f icat ions at an 25
e arl ie r age and thus make the t ree mo re vulnerable t o at t ack ( Hay
and Eage r ,
Large t rees , on the o the r hand , hold the larges t ad el gid
populat ions . In addit ion t o their bark charact e ris t ic s and
pot enti al t o support the larges t numb e r of adel gid s , they pres ent a
t al l prof il e and theref ore are ab l e t o int erc ep t airb orne adelgids
l more readily (Hay e t a . ,
The devel opment of infest at ions in the Great Smoky Mount ains
National Park sugge st s that adelgid s f irs t est ablished thems elve s
- along the northe rn ha r dw o o d/ s p r u c e fir ecot one ( the b oundary be tween
northern hardwo od and S pruce-fir) and then gradual ly began t o invade
highe r el evat ions ( Eage r The high winds at high alt itude s
probab ly do not allow airbo rne adel gids t o b e depo sit ed on mountain
t op s . Ins t ead , the ins ect s t end t o se t tl e out in the eddie s on the
l eeward s ide . Gentl e thermal current s then favor gradual dis pe rs al
- from low el evat ions t owards the summit . Al s o , the mixed uneven aged
s t ands at l owe r alt itude s are much mo re l ikely t o c atch adelgid s
suspended in the air than the smalle r , pure f ir st and s on the t op s
o f mount ains .
REGENERATION OF INFESTED STAND S
B ec ause of the relatively rec ent his t ory of b als am wo ol ly adelgid
infest at ions in the S outhe rn Appalachians , the change s t aking place
in c ommunity s tructure aft e r the de ath of Fras er f ir are not ye t
fully 26
unders tood . Boner ( 1 97 9 ) s tudied the species compo sition in s pruce
fir fore st s with dif ferent degrees of infest at ions in the Gre at
r Smoky Mount ains National Pa k and the Black Mount ains . Thes e are
s ome of his ob s ervat ions : ( 1 ) Red spruc e is favored by the releas e
and thei r c rowns expand t o cover a great er area in the canopy . ( 2 )
There is an increas e in o the r tree sp ec ie s as s ociat ed with the
- spruc e fir fores t s ; in particul ar , yellow b irch and mount ain ash .
( 3 ) In the unde rst ory the re was an increas e in the dens ity of
r thornl es s blackbe rry , red raspb e r y and Fras e r f ir ; however , the
densities of mount ain cranbe rry and hobbl ebush decre ased . ( 4 )
Ground c ove rage of mo s se s and fern s dec reas ed . ( 5 ) S ub s ap l ing
dens ities increas ed with time aft e r de ath of the ove rs t ory and
Fras e r f ir proved t o be the mo st abundant und ers t ory spec ies . Al l
fac tors cons ide red , Frase r fi r reproduct ion seems abundant al though
the future of thes e young s t ands is s till unc ertain .
BAL SAM WOOLLY ADELGID CONTROL METHOD S
Orchards
The main purp ose behind the manipul ati on of fir communities would b e
t o achieve dens e young st and s of unif orm height and vig orous growth
in the hope that they would re ach reproduct ive age be fo re adel gid
at t ack . This c ould be ac c omplished by removing the overst ory aft er
the s eedl ings had roo t ed in the mineral s oil ( t o avoid de sic cation
su n from exposure o f the s oil and the ) . Thinning out st ands befor e
s eed— b e aring s t age and le aving those t rees that promis e the high est
2 8
L a r ic ob u s r ic hs o ni i thems elve s : i e , a small , dark b rown be etl e , and
S A hid e c t a the mall , yell ow ladyb ird beetle , p ob l ite rat a . The lat t e r
r is found mostly in the crown of t rees and , although prel imina y
e r ic hs o nii resul t s with L . were promis ing , it is no t the answe r t o
the adel gid c ontrol que st ion (Amma n and Spe ers The reas ons for the failure of al l thes e int roduc t ions seems t o b e
( 1 ) The lack of spec ific ity on the part of the predator it i c e a e feeds on o the r ins ect s b es ides A . p ) ,
( 2 ) Inab ility of the insec t t o f ind the adel gid s ,
( 3 ) Inab ility of the ins ec t t o adap t t o the new environment ,
( 4) The high rep roduct ive capac ity of the adelgid , and
( 5 ) The rapid de ath of the ho st ( Fras er f i r) .
Chemic al Control
There are a numb e r of chemic al insec t icides e f fec t ive against the
B a o n Du r s b a n b al sam woolly adelgid yg , Diaz inon , , Pe rme thrin ,
Chl o r hr if o s and p ) . Until rec ently L indane was the only pes t icide
regis te red fo r this app lic at ion . I t was us ed extens ively during the
' l96 o s despit e evidenc e that it pers is t ed in the s oil (J acks on e t
a l E . At pres ent L indane has been placed on the nvironment al
Prot ec t ion Agency ' s Rebut t abl e Presumpt ion Agains t Regis tration
lis t , due t o it s harmful envi ronment al ef fect s .
A promis ing alt ernative s eems t o be the use of fat ty ac id s ( Pu r it ch
1 97 5 ) and their s alt s ( bas ic ally the same as s o ap s ) which have the
nec es sary s olubility for s pray application . Fat ty ac id s oc cur
naturally in pl ant and animal t is sues and are readily b iodegradabl e . 2 9
They are har mle s s t o wildl ife and thei r phyt ot oxicity is limit ed t o
the fac t that they may remove s ome of the cut icle on le af s urfaces .
Applic ation of fat ty ac ids is only fe as ible on a small s cal e . In
order t o be eff ec t ive the s t em ha s t o b e s oaked c omple t ely and each
a s t em has t o b e done individu lly . Ae rial applic ation is not
i s pos s ibl e bec aus e the c rown is in the way . A wat er s ourc e
nec e s sary t o dilut e the insec t ic ide t o the de si red c oncentration and
gas ol ine powered high pres s ure pump s are nec es sary in o rde r t o re ach
the higher p ort ions of the s t em .
CONTROL AND POLI CY IN THE GREAT SMOKY MOUNTAINS NATIONAL PARK
Given the limit ed numbe r of presently avail abl e b al sam wo olly
adelgid c ont rol me thods . the re a re few res t rict ions involv ing their
us e . Pol icy regarding b als am wo olly ad el gid con t rol and management
of affec t ed are as has no t b e en es t abl ished c ompl e t ely in the G re at
Smoky Mount ains National Park . When the adel gid w a s firs t de t ect ed
on Mount S t erl ing in 1 96 3 , at t emp t s we re made t o c ontrol it by
6 0 0 cut t ing down all the tre es in the infes t ed are a , which was
1 0 me ters long by 5 me t ers wid e . Howeve r , ground checks the
fol lowing ye ar S howed 1 6 hect ares around the orig inal are a were
t al 6 infe s t ed ( Cie sla , e . 1 9 5 , in J ohns on The cut ting
program was d ropped aft er it p roved ineff ec t ive and the b al s am
wo olly adel gid c ontinued expanding it s range . Th e U . S . Fo res t
Servic e limit ed it s el f t o monit oring the advanc e of the pes t by
ae rial surveys using inf rared pho t og raphs and ground checks . By 1 97 8 , the b al s am wo ol ly adel gid was present through the entire
S pruc e- fir dis t ribut ion in the Park (Eagar
8 In May of 1 9 2 , a mee ting t o ok plac e at t ended by the Pa rk
S Superintendent , Upl ands Fiel d Research L ab orat ory t af f involved in
r b al s am woolly adelgid res e arch , and Pa k Re s ourc es Management s t af f .
The st atus of the adelgid in the Park and currently avail able
c ontrol methods we re dis cus sed . The decis ion was made t o s t art a b iannual pes t icide S praying program at Cl ingmans Dome us ing v ins ec t ic idal s oap . Th e s it e was chosen b ec aus e of hea y vis it or
us e , ac c es s ib il ity , and the avail ab il ity of a suit abl e wat e r s ourc e .
The high pe rc ent age of f ir in the area was an ad dit ional fac t or ; it was fe ared that if all the Frase r f ir were to perish under ad el gid
at tack , the aes the tic imp ac t on the t o tal s cenery would b e far mo re
det riment al than to a mixed s t and . Pro t ec tion t o this limit ed numb e r of Fras e r f ir will prov ide future s e ed s ourc es as well as
pres ervation of gene t ic d ivers ity . The two spraying operat ions were
t o t ake plac e in July and S ept emb e r .
Thes e part icul ar dat es were cho sen in o rder t o c oinc ide with the
u u maximum n mbe r of adul t adel gids and the le as t n mb e r of eg gs , on
which the s oap is les s effec t ive . Approximat ely nine acre s were
sprayed , c oncent rating on hot spot s in t re es highly vis ible t o the
publ ic , such as the are a adj oining the parking area , the are a behind
and adj ac ent t o the res t rooms , and al ong the paved t rail . In s pit e
of the limited s iz e of the are a involved , this cont rol program was the larges t one t o dat e using insec t ic idal s oap against bal s am
woolly adelgids . REFERENCES CITED
1 96 2 . Amman , G . D . Se as onal b iology of the balsam wo olly aphid on Mt . — 8 Mitchell , North Carolina . J . Ec on . Ent . 9 .
1 97 0 . ic e a e : Amman , G . D . Phenomena of Adelges p populations (Homopt era - 1 7 3 4 . Phyll oxeridae ) in North Carol ina . Ann . Ent . S oc . Am .
D Amman , G . . , and C . F . Speer . 1 96 4 . Rel eas e of pred at ors of the b al sam U S woolly aphid in North Carolina . . . D ep t . of Agriculture Fores t — 2 4 Servic e Rese arch No t e SE 3 . p .
1 9 28 . Ad e l ina e Annand , P . N . A c ontribut ion t oward a monograph of the g A ( Phyll oxe ridae) of North me ric a . St anford Unive rs ity Pres s , Palo
Alt o , Cal if . 1 46 p .
1 95 2 . i c a e a Bal ch , R . E . S tudies of the bal sam wo olly aphid Adelges p i s L ( Ratz . ) and t eff ect s on b als am fi r , Ab ies b als ame a ( . ) Mill . Canad . 867 7 6 D ept . of Agricul ture Pub . No . . p .
Bone r , R . R . Ef fec t s of Frase r f ir de ath on population dynamic s in S outhern M K App alachian b ore al eco syst ems . . S . Thes is , Univ . Tennes see , noxville
1 0 5 p .
. M. . . . . 1 965 . Ciesla , W , H L Lab e rt , and R T Franklin . S t atus of the
1 96 4 . U S P . F b alsam woolly aphid . . Fores t Servic e , S . . , Div . FPM , - - AS heVi-ll e N C R e 65 1 1 , Q . p . NO . 0
1 97 8 . Eagar , C . C . D is t ributing and charac t eris tic s of bals am wo ol ly aphid M infest at ions in the Gre at Smoky Mount ains . . S . The sis , Univ . Tennes see , K noxville . 7 2 p .
Fedde , G . F . 1 97 3 . Cone Product ion in Fras er f irs infes t ed by the bal s am i c e a e : wo olly aphid , Adelge s p (Homopt era Phyl l oxe ridae ) . J . Georgi a - Ent omol . S oc . 1 3 0 .
. 0 . 1 97 0 . . Greenb ank , D Cl imat e and the ec ology of the b al sam wo ol ly aphid - Canad . Ent omol . 57 8 .
. L . . K . 1 97 8 . Hay , R , C C . Eagar , and . D J ohns on . F ras e r f ir in the G reat
Smoky Mount ains Nat ional Park . It s demis e by the bal sam wo olly aphid A i c e a e USDI ( delges p , Nati onal Park S ervice Contrac t Rep . , SE
Region , Atlant a . 1 25 p .
L Hay , R . . , and C . C . Eagar . 1 9 81 . S t em morphology and physiology of Fras er U DI f ir in relat ion t o b al sam wool ly aphid at t ack pre ferenc e . S , RE io n A 7 3 National Park S ervic e Cont rac t Rep . , SE g , tlant a . p .
1 9 6 4 va s ul a r Hoffman , H . L . . Checklis t of plant s o f the G re at Smoky — Mount ains . Cas t ane a 45 . 3 3
1 8 9 9 . Hopkins , A . D . Report on inve st igations t o det ermine the cause o f s u r c e 8 — 1 8 unhealthy conditions of the p and p ine from 1 80 93 . Wes t n Virginia Agric . Exp . S t . Bull . 5 6 . 46 1 p .
- J . 1 96 4 . Amil l a r i a Hudak , . , and R E . Well s ro o t rot in aphid damaged — bal sam fir i n Newfoundl and . Fo r . Chron . 7 6 .
D . . . . . 1 97 4 . Jacks on , M . . , T J Shee ts , and C L Moffet t Pe rs is t ence and
movement of BHC in a wat e rshed , Mt . Mit chell St at e Park , North 7 — P - 0 Carol ina , 1 96 7 2 . es t ic ide Monit oring J . 2 8 .
K 1 9 80 . : Johns on , . D Fras e r f ir and the bal s am wo ol ly aphid Summary of RE R s o u r inf ormat i on . S outhern Appalachian . / e . Manage . Co op . Rep . - Pp . 2 8 6 2 .
Ko tin sk . 1 91 6 . n Dr e fu s i a i c e a e y , J The Europe an f ir t ru k louse , Cherme s ( y ) p — 1 6 Ent omol . Proc . S oc . Washingt on .
Mc Cr k n Cl eb s ch 6 a e , R . J . , R . E . Shanks , and E . E . C . . 1 9 2 . Soil mo rphol ogy
and gene s is at higher el evat ions of the Great Smoky Mount ains . S oil - Sci . Soc , Am . Proc . 3 8 8 .
Mitchell , R . G . , M . E . J ohns on , and S . A . Rudinsky . 1 96 1 . Se as onal his t ory
of the b al sam wo olly aphid in the Pac if ic Northwes t . Canad . Ent omol . — 7 9 8 .
Oo s tin J . 1 95 1 . S g , H . . , and W D . Bill ings . A c omp aris on of virgin pruce
fir fores t in the northe rn and s outhe rn App al achian sys t em . Ec ol ogy
Pu r it c h 7 , G . S . 1 9 5 . The t oxic ef fec t s o f fat ty ac ids and their sal t s on
ic e a e . the b al sam wo olly aphid , Adelges p Canad . J . For . Re s — 5 2 2 .
Pu r it ch , G . S . , and R . P . Johns on . 1 97 1 . Ef fec t s o f infe s t ation by b al s am i c e a e woolly aphid , (Adel ges p on the ul tras t ruc ture of b o rdered
pit memb ranes of grand f ir , Ab ies g randis (D oug . ) L indl . J . Exp . Bo t any - 95 8 .
SARRMC 1 8 . 9 0 . Fras e r f ir and the b al s am wo ol ly aphid : A problem a nl ay s i s
25 p .
K Saunde rs , P . . 1 97 9 . The vege t ational impac t of human dis turb anc e on the - P D spruc e fir forest s of the S outhern Appalachian Mount ains . h . . N O 1 7 7 Dis se rt . , Duke Univ . , Durham , . . p .
. O . 1 97 8 . Schooley , H . , and D . G B ryant . The bal s am wo ol ly aphid in N-X— 1 6 7 2 Newfoundl and . Canad . Fo r . Service Inf ormat ion Rep . 0 . p .
S ic cama . G . Vo e lman 1 9 82 . S , T , M . Bl is s , and H . W . g . Decl ine of red pruce - in the Green Mount ains of Vermont . Bull . Torrey Bo t . Club 1 6 8 . 1 8 Spe e rs , C . F . 95 . The b als am wool ly aphid in the S outhe as t . J . Fo r . — 5 1 6 .
A 1 96 9 . St ephens , L . , J r . A c omparis on of cl imatic el ements at four M elevat i ons in the Great Smoky Mount ains National Park . . S . Thes is , K Univ . Tennes se e , noxv il le . 1 1 9 p .
a 6 Whit t ke r , R . H . 1 9 5 . Vege t ation of the G reat Smoky Mount ains . Ec ol . - Mo no g r . 80 .