C SOUTH EST
FOREST SERVICE
U.S.DEPARTMENT OF AGRICULTURE
P. 0.
BOX 245, BERKELEY, CALIFORNIA 94701
BLACK TW G BORER. . . a tree ki er in Hawaii
Robefl E. Nelson
USDA Forest Service
Research Note PS W-274
1972
AD@rac$: The 'bllzcllr twig borer ( X y l s ~ d r - l s m
s mpctus Eichhoff), &st discove~edin. NawaG iji 1961,
has become widespred on m a w host plants thoughout the islmds Beetle Seshtions have caused heavy
associatd with death of apparently vkorous trees in
forcest stands The beetle and its asso~atedmjlcroorgmisms hwe beem identgied as assodat4 with the
death of five tree specks in plasleerl forests on B a h .
gbmulI;r"era; MehIeuea bumMemxylora; phmtation sbmds;
Clifion J. Davis
The black twjlg borer (Xybm&rw compacilw
EickLXloff) and associated ficroorgadsm have kded a
s m l l number of trees of several speciqs planted in
windwad Oahu, Hawa~.This is the fkst report of the
death of well-estabfished, large trees in HawaG that
can be attrril>utedto these orga~sms.Cuton J. Davis
and other entomlo@sts have p~reGouslyconffarmed
the associatiron of this insect with the a h g of small
trees and shrubs in HawaE.
In early December 1971, Robed E. Nelson noticed
dead tree crowns in severd sml_apatches of planted
hrests on the lower norlheast flalzkh of Mount
Olornana. The planted stands affeded were of five
spedes : brushbox (Tristan2 co~ferta)~
t larpentinetree (Synearph gbmukqma), paper-bark (McelaIeucas
Eeucadedrorz), redironbark eucalyptus (iFLtw@ptw
saert.o=aybplj,and blackbutt eucalyptus (EEpilukd).
Exarruination of the dead trees showed thzbL twigs and
branches were heady attacked by what appeared to
be the black twig borer.
In J a n u ~ y1972, we e x a ~ n e dseveral trees of all
qecies in these stands. Mter sgeclinnens were collected, the black twig borer was positively identified
as heady hfestiing both dead and live trees and was
associated with KUed twigs and branches. No cause of
tree death sther t h n this hsect pest and assodated
~ c r o o ~ g a d s codd
m
be deterdned fiom these
exadndions of tree trundrs and root crowns.
The first h o w n idestation of the black twig borer
in Hawai was discovered in. Novewaben: 1961, at
Qlua, ~ a h u , 'just a few miles from the kfesitation
reported in this note. Since then the beetle has
becorn widespread thoughout the Hawagan Idands.
~ o b d y \ r e ~ s ~ e the
d association of the black twig
borer with mo&afity and dieback of Eucabptw
mbmta trees durhg $rou&t p e ~ o d son svere sites
on the island of Quai. Host plants of this &sect pest
now m d e r more t h n 65, ranmg from orcMds to
large trees.3 These reports suggest that the black twig
borer m y beeome a s i o u s theat to foreds in the
-
Wawa5an Isknds. The specific conditions under
which it can eaus extensive damage md the identity
and role of asociated dcroorgaPiliism are not known
and need to be h-nveskigabd in cletaa.
SPECES AFFECTED BY mFESTATIONS
The infested patches of forest were probably
planted in the 1930's. They are on ridges, side slopes,
and wales, on generdy steep topogaphy. Soils are
va~ilble,from mderately deep to h a o w a d rocky.
Elevatlion r a w s from 200 to 400 feet. Annual rainf d averages abo.cal40 hches.
We found that severd spedes of understory. shubs
were also I n e a ~ y inresled, iracluhg koa haole
(P;eucaem ghum), guava (PsMium g.lkajava), vervah
(Sfaehy~arphe~ck
japlua&nW,
and Christmsberry
(Schinus terebiiathifolk). Koa hraole is one of the
prefened hosts of the black twig borer. Becablse this
on in t k s area, it has probably contriopdation buildup, leading to subsequent and persistent attacks on large trees. Our study
of the species affected showed the fsnowing:
Paper-bark: many of the trees with completely
N e d crowns had hedthy carmbium tissue ;and were
sprouting vigorously along their trunks. In spite of
heavy infestations, few trees examined were dead.
Paper-bark trees were mostly less than 10 inches
dia~neterbreast height (debh.) and up to 35 feet tall.
The few dead trees k'ound were smller than average.
@
Red-honbark: several of the trees with dead
crowns were sprouting vigorously along their trunks,
but o"ters were dead. A few had thek csmns kued
many months previously, with subsequent trunk
sprouts which had then recently died. Large and
apparently vigorous trees had been killed, such as one
14 inches d.b,h. and mother 11 inches d.b.h., both
nearly 60 feet tall. On some twigs beetles were found
trapped in gum exuded from the bore hole.
Turpentine-trees: some of the trees with
completely dead crowns md trunks had one or more
vigorous sprouts several feet tall rising from the root
cram. However, the size of the sprouLs and the fact
that m n y trees wi-th healthy crowns also had such
sprouts make it u a e l y that sprouting was necessarily associated IN
e beetle attacks. Turpentinetrees growing in
ure with paper-bark trees
suffered Iaea~erm o d d t y from bee"cle atQsks &m
did the paper-bark trees. Yet, a pure stand of
turpentine-trees had only a few kiued trees. Elsewhere, a group of six turpentine-trees were a e d , but
one tree in the middle of the group appeared hedthy.
Large, appaenay ~ g o r o u strees were med; one
was ma* SO feet tall and 13 inches d.b.h.
Brushbox and bhckbutt: Trees with dead
crowns were not sprouthg. The ~ m b i u mtissue was
dead on the lower truks, AU kiiEned trees e x a ~ n e d
had adapparently been Ggorous before the beetle
attacks. One a e d brushbox was 12 hches db,k. and
39 feet tall. A U e d blackbutt tree was 16 hches
d.b.h. and 60 feet t d .
BLACK TWIG BOWR
The black Wig borer L native to Ask, but has
wide geograpEca9 distribulion. Bes range hcludes
Africa, and Mahysia as well as Hawag. In North
Amdca, it is fomd o d y in Flosib.
Twigs and bran&$ are usuaUy the prefened
targets of adult beetles and, in many instances, only
one to t h e e beetles and thek brood are sufficient to
the twig or branch. Dieback of dfected twigs and
branches follows, spreadkg throughout the tree in.
some species. In some species, the beetle will attack
the bole of sapfing or poke size trees.
Indpbnt infestations are often dgficdt to dele&
in the Eve brmches. But as the kaws wither and turn
yellowish-brown, infestations are readily detected and
cod~xned.
The work of the black twjlg borer in the tree
species reported here is typical of that described
elsewhere: Beetles bore into twigs or smll branches,
up to about 1/2 inch in dhmetea. Live beetles are
fourad in. twigs of both live and dead trees. Successftll
borhgs penetrate into the pith, w h r e the beetle
excavates a. brood gallery, Many beetle borhgs are
not c o q b t e d , some barely started, then abasaaloned,
The physical darnage done by the borllnag beetk is:
d n o r , relative to the size of most t ~ g atbcked.
s
Yet
,
h U o w stads, can
the
any borhg a c l i ~ t y even
twig. A l m d kva~iably,s b k and lesions from fwgus
or sther orga~smsare asoclated vrith borer hobs
md twig death.
NOTES
'Beasdsley, J. W.The bb& twig borer, a. ptenthbly seriou~
pest of e r n e new to Ilawaii. Haw. Farm Sci. 1341): 5-45,
1964.
%obdy,
Robert. R e p v l on mrlalr'ty and dieback o f
Euecs&pkus robust&. Haw& Div. FOP,, Forest Manage, Note,
Kauai, No. 1 , 2 p. 31966.
3 ~ a v i s , C. J. Bhck twig borer threatens m f h e .trees.
Newsbtter, Haw. Bot. SOG. 9(5): 38-39. 1970.
"~avis, C, J. Xyleboms mrstafti Hagdorn. A r e p r t on the
mffee-tw& borer. PZOG.Hawaiian ErPl;smoL SOG.:18(2): 197.
1963.
Davis, C.J. Noles on new and old orehs pests in Hawaii.
Pac. Orchid Soc. Bull., p. 13. 1964.
Kakshoven, L. G. E. The occuvence o f the ppa'mry twig
borer (XyEeZiorus morstatti Hag.) in Idones&. Entsmssl
Berichten 18: 220-252, 1958.
The Authors
ROBERT E. MLSON has been in change of the Station9s timber and
watershd resource development research 51 Hawaii since 1957. He join&
the Forest Senrice in 1941 after e m k g a 1Fo~estrydegree at the U~versity
of Callifornh. CLIFTON J. DAVIS has been State Entomologist, HawaG
Depab-ernent of Ag~culture,since 1961. He earned a B.S. degree in entam l o g y at Utah State University in 193'7. He jshd the State Depadment
sf Agriculture in 1948, after empbyment by the U.S, National Park
Semiee in HawG.
U.S. Forest Service research in Hawaii
is conducted in cwperation with
Division of Forestry
Hawaii Department of land and Natural Resources
The Forest Service of the U,Se Depadmend of Agriculitwe
. . . Conducts forest and range research at more than 75 locs~rionsfrom Puefio Rim to
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. . . Manages and protects the 187-mlllim-acae National Forest System for sustained yield
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The Pacllc S~uthwestForest and Range Experiment Sgaaan
represents the research brmch of the Forest Service in California and Hawaii.
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