SPRUCE- 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 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

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 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 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 .

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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 .

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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 .

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