The larger corn stalk-borer

I i.L -._ --.-. -.Y A
CIRCULAR No. 116. I

United States Department ,1i',ic Iliiir

BUREAU OF ENTOM ?r, ',..-
L. 0. HOWARD, Eti,.r..n> ,., i and i; &..I" Bureau.


TIlE LARIGEI (ORN STALK OIIll.4' -
( D iffiatra- ,i hrq' iit. I'' l).1


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By (;IEol(.Iv G. AINSLII,,
AssociatC ' xHor of Entomtno lin. ('1icm,in AOriicultn'il ('alh/i f S"-ltli
('(a'rolhilK.
INTWI4I)' TION.
In mily s1oit11 othrn cornliihld n lheavv wind laic'in hl, .eilI sotll. lie-
fore the corn is inlatIreld, does (,remt (dninnme l l)reAMkii. tin' plamnI,


offl at the surface of
the -',iii .l 1 thus
i ,iiin ,-i.1 them An
examiti(4n Itf these
lroktn steis will. ill
mo1(st cases show that
they I have (een
ir 1.1 i\: weakened( d b)v
the burrows oIf a
l;irva or caterpillar.
This larva ( 1i". 1) is
known as "ilthe ar-
i.r corn -ta4lak-borer "
. D0;,t/'a 1 w:cc<'
i;8). Its work is
1ar-' .l. within the
tQem of the pllat and
is so coeca ledtI that,
in Ios cases(I. linless
l)Iresnce of ttlie insect


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F''l;. I1.T ''ie> lurl'+,r <'i)rln s-liilk-lxnor+r


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at, StlIIII r F 'or ll oHf klrv : b, ,I, l ,il,' i ;i li1 t'W I Fl'H I
latrva, : 4, third Ilhora icic Nc iii<"ii! frIo l .i], : +, i it'lI
abdo liIii s<-:;i tfr ni al-)DV<; -11. fliK I'romn sifle, li, -', IEii;lnry'd ; i1, +, f,
still I ola l I.n,.'H (l. ItoI niLawn f1roi 11 l w:1rd. I
weather conditions make it conspicolls,. the
passe", unnoticed.


'I ll- is 1]t.i 'ti4zitlly nl rt, isio l ofi" ('irciular N o. I G. i Ir e I iiI( I Ic: I .\ Y1 .t 1s
:\)f.) l,\ 1'r. L. 1>) toward. Mr. h A slit, was fo(rlllerly ill Ihv *+lldl3Y of+ this
IB ll'ti'fi: as milt I ''lll filil ex:!'rt il c'tl ,;I :111d t"(oratge illsevt ihlv<>s iislif)IlS :17ixl
thli- pest wNs t(le ''f ti l, Iu)ts of If,' --lationt assi..cI to hiimi. II'e after-
wards did snIIt \ wIrk I11)()1 thie sl'tvis fo,41 tilh So(IIIIi (rXIrolilla Agricitltltral
l'\|,'1i'ijiii St' titlth i ill (ootiieratilin with this lItlreial.
"17"l--No. 11 G-10


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This insect seems to have been originally an enemy of sugar cane
and to have first transferred its attention to corn in the southern
)iart of this country, where corn and cane are grown over the same
territory. It occurs in many countries where sugar cane is the staple
crop, and has caused great *1;1;:ige in the West Indies, British Guiana,
Australia. and Java. The bulk of the evidence gin,. to show that it
was first brought into this country with the importation of sugar-
cane cuttings from the West Indies and Central and South America,
where, since early times, it has interfered with the production of this
staple.
In the United States this borer is found almost universally through-
out the South, from Maryland to Louisiana and westward to Kansas.
Among other localities it has been reported to the Bureau of Ento-
mology from Bennettsville, S. C., as destroying corn, especially that
planted early in the season. From WVaynesboro, Ga., in 1909, reports
were received that in some fields the corn was "at least one-third
destroyed by an insect which later proved to be this species. In
Virginia it has been found recently at Nathalie, where it was studied
l)y Mr. J. A. Hyslop, of this Bureau, at Allenslevel, at Church IRoad,
and at Farmville. In late October, Il'.i', Mr. E. G. Smyth found
that nearly one-half of the cornstalks at Diamond Sj)riii-. Va.,
were infested, often as many as three larva being found in one
stalk, boring from the surface of the ground down to the base of
the root; and while the author has frequently found as many as
a dozen larva? in a -ii _h'e stalk, there are never more than two or
three pupa' in the same stalk. In each case it had d;ii;ig,'d the corn.
and especially that planted early in the season. I)etailed investi-
gations of this insect have been conducted by the author during the
last two years, chiefly in South Carolina.
NATURE OF DAMAGE.
Corn is damaged by these caterpillars in two ways. First, in the
early part of the season, while the plants are small, they work in the
Throat" of the young corn, and if the tender growing tip within
thlie protecting leaves is once d:ii:i_-,(d all chances that the plant
will become a normal productive specimen are gone. In many see-
tions of the South this is commonly known as bud-worm injury,
amd though there are several other insects which cause a similar
mutilation of the leaf, a very large proportion of the so-called bud-
worm damage may be ,.i '.l to this insect. The effect of its
work on thlie leaves of (he young corn 1)plants is similar to that re-
-,i]i ing from attacks by the corn billbugs (S//tieHlop /i/orI splp.) and
is eviden ced by thle fa1.miliar rows of small circular or irregular holes
across the Iblades of the plant (fig. 2).
T'le other form of serious damage li:ir.:';,l'e to this pest occurs
later in the season. The larva-, havini. then left the leaves and
[Cir. 1 16]




3

descended to tile lower part of the stalk, tunnel in the pith. ( See
fil. 3.) If the larva' ar' at all iniiiiromis in the stalk, their burrmow
so weaken Ilie plant that aiIny IIIIIusual stiaiii will lay it low and
destroy all chance of its maturii'1l. While frequeitly I' ten or more
larvaw may live and mIat lire ill one plant. it 1must be reieembliered that


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Ji 2.- Work of larg''r corn, 'talk ih im n lilali of Ir a' .f r lr bl larva'.
;r<';itly r>'idii<-,l. O( riinal. I
.any inifestation, however light. will hle-ssen iln some d, l .r Ih' xvitalit v
of tlle planilt and cause a corresponding lo-ss in the quality and quan-
tity of lthe harvest.
HABITS 01 TIl LARV.AH .
Ime ildiately ponl leaving thle -2. in spring, tlhe vo ii,- larva of
th iir-t I ", iition, spiilinig a silken thread behind it. xxlanilders
doxxwn into the throat of the plant as far as the water orl dew riisuallyv
>nailii1. there wxill allow it to go. and ,,.._ to feed on tle leaves.
goiln" back and forth through the e(t unfolded clusters andl soon
ridd'Y'1-. tie more, tender leaves with aimlevss bulrrows. If the bur-
rowV readIWes ihe tender terminal bud where tlie future joints are
beinl formed, further growth at that point ceases and the plant be-
come' stuntlted and misshapen, with no tassel. As the plant continIIe
to mature, the larva "- ',,ws -ut." as the farmers say. It is more
Icir. 111]






likely that it is the evidences of its work and not the larva itself
that "grow out;" but for whatever reason, the caterpillar soon leaves
the more leafy portion of the plant and attacks the stalk at or near
the ground. Here a hole is cut through the outer wall of the stalk
and the larva mburrows upward for a short distance, after which it
seems to run aimlessly throu-h the pith, frequently even leaving the


FI(;. i he larger corn stalk-borer : Larva in lower pnrt of corn plant preparatory to
hibernation. It educed. (Oriinal.)
stalk entirely anid reeniering it at another point. Turning upward,
the caterl)ilhar, when fully grown, bores toward the outside and
cuts a circular hole in the outer wall of the stalk. Then, after
spinning a few loose threads across this opening to keep out un-
desiraible visitors, it retreats a short distance, plugs the burrow below
with -i., -ted pith, and inii the chamber thus created slowly changes
to the next or pupal stage (fig. 4, c).
[Cir. 1 IW;]






Seldom is the stalk dallaged above thle third joint from the 'rolmd,
althou-h the larvaw, whenl small. are folld in the lahrl midril- (if
the lower leaves and later in thle sea-ol. whelin ihe I',oIl Supplyl, is.
restricted, evell in s-ucculenit nulbbill> t'l'thel.r up]. Tliy sometimes
also penetrate tlie ii l ,,L ili part of the stllk ill foetlingi and eltlier
sollie of thle liij'i' brace roots for a short di-ita'ce.
The larva' of tihe second geWeraTholl wiik 1n1 a -ir ill nr mallner'. exept
that atl tie tniie they appear tile ltass-cl lias loiei fortlledi: iielice the
l.lii .e Is ilow colitil led il,,.-,.her to tlhe Io er stll. Thll-. il-tead
(of arralliill to pi:ass tle pupal stla"e ili lie llipper l '-tall. thlieV peie-
tirate to thle root to hiter-i
nate alnd there, s lV. .-- ar- e .
pass the wiliter in a (fui- :
eseelit state (V. 3).... ,

SE.\SONNAI. IIlSTO iY.. *-
//' ".
Duril-1" tle \winter tillj t4 2
el)11nem of corn I > to I- I
foulltd a's ; robilst, creI amyl \ ll, ........... .........
wvliite larva of the secolilnd N" ,.
relleralt ion il Ilie t ow iier
l)art tof tile -talk o of 'j "- oro
tlhe stulbble. i'. :1- is 1lsU- Q, O+
all tie eas. I tile coil 0. -M
lias lbeel rut. In tills Io- I,,^ i ,,, i,^,, ,. t,,,, ,,/ ,,
cationm thle Ilarva forill- a tmoilh: b. win: ob, rl ,, l~tplm. All s In t
S111,1l baiylelow OWi 11 L
flnn] c a t II: -(" IIII wh m ph 1.-4r )1 e b (A'( fI )II I 1t 1.( 1 1 -t ;
fa1I of tI le Ilra IkI d wl I )roIeet I 'oi 1I-irh- 1 1 I /ceI l s i ) cl.
Ill I li tlavoralile \weatell r tIIlillit ioils. IloiliI tiie tilin fIh e Io-I ll i-
lialllret inl tlie fall until ab~o/t corii-1phlin ii '* timlle in tilte sprliti,>; tlins
catel'pillar r I'ellailns i ai:cti \e. A )mo it ll lie le 1 tile I 'I oilill i- Ili's bIw
prI-epl)ar'ed fo( lr -tn, lI. froin )I arc't h 15 to Ap ril .,,. klelle llndiiie" ,ii (IeI 1
locality, this ila va li II,-'"'e i to 1 111, r d i-ho-1 \lw u I I p it or clirv.-aIi .
(l.2.-- I. c). A flter a1 I'lrl lilerl period o f tell or iiIlOn diaYl llMCival\'ItY tltw
aduillt ill-ect el:i .I - l ill til' ( l p ipa ci-I' as ai pale ir w ish1l liw
ilotli ( fig. -, (1. /') ,w it ii l -a l r il of 12- of a'out iall iicll 11(i :l 1 I wll' i'.
TIle otlis Ii te alld Owe feolilles ', .-'in at on11ce to deost,-it c
onil tle illilder-ide of thle leaves, thie li'Vaw lhatclilng' fro1 lllhe- t'
f-. i' liii* '', th e ti-sl ._ it i.
Thie "'.l", liatclh in from teve to le days al11d lhe ho11/w lal\;
I, I t, l e their dlestl-Ucti"ve N\orl iI t(Ie upp1 ewr Ie fv Ioi'Hio ()I oftle I lii, l.
later deseliilding to thle ba-v of (lie -talk. wheretI I tilke attailll full
1'lowthi. This period. flromt e' full '_'il]i o iilaixa. lreqlliirle- frlli1
twenty to thirty days. oi, id.,lj_ h!,ly oil thle weathlier colndtiotns
[Cir. I I(]






and tlhe vigor of the plant. The larvae when full grown pupate in
the stalk, usually in the second or third joint from the ground, and
in from seven to ten days the adult moths of the first generation
emiergre.
The ..g- for the second generation are laid in similar positions
oni the lower leaves or on the stem. and the larvaw, after feediii-, for
aI short time on the leaves, go directly to work in the stalk, completing
their larval -rowth in the pith of the lower stalk as did the larvae
of the lirst generation. No damage is done to the upper part of the
plant by larvaV of the second generation.
By the time the larva, of the second generation are full grown
tlie corn is rapidly nearing maturity, and, instead of pulpating il
the stalk, they turn downward, penetrate to the extreme lower tip
of the taproot, and there form a small cavity in which to pass the
winter. At this time thlie larva' lose the darker i,:,riLg of the ear-
lier forms, and as overwintering larva' are creamy-yellow in color.
They are p1)lump) and active in the fall, but flabby and sluggish after
fasting thi, I,-liout the winter. The only way in which the insect
pa-es the winter is in the form of this overwintering larva, found
below the ground in thle extreme lower tip of the corn roots. Two
generations a year appear to be the rule. although it is possible that
in the far South and on sugar cane a partial third generation may
occu(llr.
DESCRIPTIONS.
ELI//.-The ,. are flat and scalelike. almost circular in outline,
anmd are placed in rows Or irregularly overlapping one another
shingle fashion. From two to twenty-five .-' are laid in ,'n(- place
oni the un(derside of a lower leaf or occasionally on thlie upper side
an1d o( the stem. (Creai Ny-whiite when first laid, they gradually
changee to a reddish-brown, and in seven to ten day s a iiinule. bristly,
reIddish caterpillar cracks the shell and crawls out through a narrow
slit at one end. The eggs are about three one-hundredths of an inch
(7.G mnm.) long anmd about two-thirds as wide. After li,.i.lii-r. the
white papery shells are soon washed off the leaves.
La.r,'a.-The larva of thlie first generation (fig. 1. a) when full
grow\nIl is a robust, dirty-white caterpillar 1 inch in length, thickly
covered with roilund or irregular dark spots, each of which bears a
short, dark brwistle. When the larva is small these miarkiLI- arc
almost colitigilolus, giving thlie whole insect a dark color and a hairy
appearance. The head aind thoracic plate of all the -1ig. are
broiwinish-yellow. The overwinter.ii-, larva of the seTond generation
(fig. 1. b, after thle last Iolt remnainlls unspotted and light yellow in color.
except for the head and the thoracic plate, which retain the brownish-
yellow of the earlier stages.
I Cir. I WI






PIrp",.-When first forme(Ld, lthe pupaI (fit. I. ) is light honevy-
ycllow in colors. soon (i.iiiLi to a ric(h mahoganyx-owin. It i-
about stv-en-eighllths of an inclh in lenghtli ali(i is :le to h iiotolrtt itslf
violent Iv xwho disturleld. It lies in thle cav'it Uisai+lv w ith the h(ead
up). ()n .*ii.Lr.ii', the ]notli hleais the brownish sIi hell of tlle piupa
case. partially witlhdrawn fromn tihe hole.
Afdult.-ThRe feale moth (fig. It, ) varies in coloh)r lfro almost,
white to smoky yellow. Ti'( fo'rex wiln-),. which spreadd to ahboutl 1
incles, are i dark'ler thlan tilhe hiind wihy,_, and War fahitnt i! iilil'1s.
Whven at rest th(le wia,- are hield close to the iody.. forl'millu an acute
tri:i, iiL' Thie e-,r laviiI_' is donet for t(e imot part either at night or
in tlhe lusk of eveningg, thle imoths. fl'yiL2 rapidly froit l)lant to plant.
Th ideale limioth (fig. 4, /) is utisuall-i somewhat darker inl color than
the female aInl always smaller.
FoIolD) PLANTS.
BIeides corln and ,,ILn...r cane, this borer hias beel reported :a- feeid-
iiil., on i1rirlnihm, Johnson iig'a-s. guinea corn. and gi raliia girra-. ThIe
injury to the four last-muientiit i4l eIlants i- exver sexvie. l)it iin lan-
ninii,, metlhodsl of (oitrol the' mi ust ie considerel anil an examiniatioli
made to determine whetliherr or t they are harborii.- th(ie pest.
NATUlRAL (I E'KHS.
The lar..' corn stalk-lborer lias very few natural enemiies. A
minute IIyieuiioipteroii- parasite ( "/'r Sl, ,,ip i' ,, i,<'n<., Itiley) has
in a very few instances beein found living, in and detroyinxi th(e egrg-..
It one clase ten of tlhiese minute Ipairasites wel re read frnt twoo x ;.
The larva of Ia lrown. velvet eet le ( (nh ((L /Ftl./iiiil; in sip/ l!inf1is,
De(G.) sonietiMie( elners (the Iholes in the stallk of stu=le ah Ifter the
corn is (ut andl devoou'rs' th(e c(aterpillars found therein. T'lis larva
has bleen foutnd(l to le (of great x'lule in reu, in tl' lthe nulber', of th(e
blorers in fields of -iI,'.I calie. The teriltitc. orv white atlits (7 r ii'
7",';1f.\ Koll.). locally known as "- wool i." have lbeen ol-'rvedl
dest ro\ ii,._ tl le arvwe in thle stullhle in th(lie winter lter a pptoh ara ently
only wvhen (the pree(We of thie lamrv e inter'fredl with I lie w (rdk of tli(,
alilts. Ill a few cases bodies of the borer- have leen foiuild iln t(he
stubble kilhledl I a fliiL''-. ia a tas ye+t lndleternied,l which envelp- their
bodies ill a white mold. Funl"ii, howvxeer. are too deelidheit oil
weather vondlitions to le of any practictal value in conitrolliur thie pIest.
P'lR EVENTIVE MI lA +, .
Isotation is one of the W-1 greiilcral pr 'venitive of inijur froml ii-
sects all'h ct ili, field ('rois. lExlerie'i nce li m a-wn tai t where corl'
huas followtdl it-elf upon tlie sae li ield for r tw)' io ot e vearl's tlie',
lihas been a Itulch greItler lo-s. fomi thl e borer thian Wxxlre an avnnaiil
e'i:i-.' of crol) hl.as lieen practiced. l'hii.s is especially noticeanbllh
[Cir. 1I!)







where stalks or stubble from the previous year have been allowed to
remain undisturbed throughout the winter. The moths, upon emer-
gence in tihe spring, finding themselves surrounded by the young
corn. commence ',, laying at once and escape the dangers encountered
in searching for another field of corn. A forced journey in search of
young corn results in many of the females being eaten by birds or
being destroyed because of rain. cold, or failure to find the object of
their quest. A few moths will always succeed in their search, but the
successful proportion will be greatly decreased by persistent crop
rotation.
Another remedy, probably the best for this insect, is the thir'oii,,h
destruction, some time before the period of ,.*]rg",gr'e of the moths
in the spring, of all the stalks and stubble i-Iii:iinuii, in the field from
the preceding crop. If all this trash can be disposed of before the
opening of spring, the numbers of the pest must be greatly diminished
if not almost exterminated, for the only form in which the insect
passes thie winter is that of thie caterpillar, and the only known loca-
tion is in thie lower tip of the corn root, snugly hidden. Some few
imay. however, libe found to survive in the roots of the l.r.er grasses
mentioned above, and care should be taken in such cases to treat these
in the same way. Thlie method employed in disposing of the stubble
and stalks will depend largely on the conditions in individual cases.
If thle stubble is cut low and the land is moderately heavy, a
thorough deep plowing may suffice, an inch or two of well-settled soil
b1)eing suffiicient to prevent thle escape of the adult moths. Bri lring
the stubble to the surface where it can dry will kill some of the con-
tained larva. but this. method depends too much on the state of the
weather to be trusted. By far the most effective plan is to remove
the stubble from the field with a rake and burn it.
In the cane field the methods of treatment must be ailjusted to
correspond with the methods of handling thliat crop. ThIe larvae conm-
imimnlv spend the winter in the trimmings and tops which have been
discarded at harvest time because of immaturity. This refuse, left
oin tlie ground thrii-li,,it the winter, becomes (dry and inflammable
an1d, if thoroughly burned before spring. ,',iii, li larvae will be killed
to insure at least temporary relief from the rav.i,- of the borer.
Any method which will insure the complete dest-rutction of the over-
\wiNitering" larvae, i' persisted in and carried out simultaneously over
lar ge sections of tlie country, will effectually preclude serious damage
from tlie insect.
"of'J DOCUIJMENT

#('/k 1ar17 of l r'irlture.
VWASHINGT'roN, I). (C., D) .clnbcr 14, 1I'"1.
[Cir. 1 10]
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UNIVERSITY OF FLORIDA

3 1262 05252 3270