Control of the pale western cutworm in the southern Great Plains region


Material Information

Control of the pale western cutworm in the southern Great Plains region
Physical Description:
5, 1 p. : ill. ; 27 cm.
Walkden, H. H ( Herbert Halden ), b. 1893
United States -- Bureau of Entomology and Plant Quarantine
U.S. Dept. of Agriculture
Place of Publication:
Publication Date:


Subjects / Keywords:
Cutworms -- Control   ( lcsh )
Insect pests -- Control   ( lcsh )
Wheat -- Diseases and pests -- Control   ( lcsh )
federal government publication   ( marcgt )
non-fiction   ( marcgt )


General Note:
Caption title.
General Note:
At head of title: U.S. Department of Agriculture, Bureau of Entomology and Plant Quarantine.
General Note:
"E-519 ; December 1940."
Statement of Responsibility:
by H.H. Walkden.

Record Information

Source Institution:
University of Florida
Rights Management:
All applicable rights reserved by the source institution and holding location.
Resource Identifier:
aleph - 030271119
oclc - 607920148
System ID:

Full Text

E-519 December 1940



By H. H. Walkden, Division of Cereal and Forage Isect ivcs nations


During recent years the pale western cutworm (A ois o x n oLa
Morr.) has become.a pest of considerable importance i the small-grain
areas of the southern Great Plains region, Prior to 1911 this insect was
not known to be of economic importance in this region. In 1911, accord-
ing to Arthur Gibson, it caused extensive injury to grain crops in southern
Alberta, Canada. The first known outbreak in the southern Grest Plains
area occurred in 1923. Since that time outbreaks have occurred -t intervals
in various localities in the western parts of Kansas and Oklahoma, the Texas
panhandle, northeastern New Mexico, and eastern Coloadoc, In the spring of
1936 a severe outbreak developed in western Kansas and was still in progress
in 1940. In 1939 and 1940 this cutworm caused extensive Cairage to winter
wheat in northeastern New Mexico.


The first sign of damage to winter wheat is usually noticed about
April 10 to 15. The greening wheat fields begin to "fade out" in spots,
taking on the appearance of wheat killed by drought. These spots enlarge
rapidly, and frequently the entire field soon is destroyed, with the ex-
ception of a few spots where harder soil prevented penetration by the cut-
worms. The greatest damage usually occurs during the last parL of April and
the first week in May. In this period the worms consume the largest amount
of food. The rapidity with which a large field of wheat or barley is de-
stroyed is one of the astonishing characteristics of an outbreak of this

Plants attacked by the pale western cutworm usually are severed below
the surface of the ground. Working along the drill rows, the vorms pass
from one plant to another, cutting them off at or just above the crown.
Feeding occurs almost entirely underground, and at a depth depending on
the looseness of the soil and the position of the moisture line. The
worms are unable to penetrate hard or crusted soil. This fact accounts for
the small areas which escape injury in most infested fields.



The pale western cutworm usually may be recognized by its smooth
and shining slate-gray color and the absence of body markings or stripes.
The head is light brcwn, wih a vertical darker brown band in the center.
Then veered from the front, this band has the appearance of the letter "H."
The absece of any markings or "freckles" on the sides of the head distin-
guishes this species from all other co-mon cutworms.


The fa3e Psern cutworm has but one generation annually. The
erposited i the soil by the parent moth, or "miller," late in
Sept. v carly P Ocoer These eggs are very s-all, about the size
oee they r placed in the soil, it is diffi-
cult I, The eLgs rmin in the soil during the ensuing winter
ann o Ltf n ig rhe first arm days of tho following spring,
alth,. i L 'y Io s ly occur during war! spells late in the
fall ,' the ,t Th ly hatohed larvae, or worms, feed at
frt h r i of wht or other available food plants. This
c riy snl or .ves the leaves a raged or skeletonized
por 7 Soo he' o the sfac of the soil unless c xcess moisture
br.g t to e s eing continues throughout April, and by the
i7o t mjority of the worms have reached their full growth
and > t I-/ ine length. In northwestern nsas a small
prcpo 'ho ,os bce observed to feed el! into June in some
so ( ul y trd te ;,crns construct s'al elliptical cells
from t to 4 i :ches 1elmw t U ,urface of the soil, deoending on the depth of
the I oe or "harpc

construo n tir cels, the w or~s bcome~ inactive within them
as t ery 'i A st, ven they transfor'm into the pupa or
chryh .ansition period from the worm to the adult,
or e then development is; ~cmplote, the moths begin emerging from
the iu ul late .. p b r' crearly i. Octobr. After mating, the
f(ep" siting C Js in the soil, thus completing the life cycle.
TI l (ig ih Vht, ad if automobile headlights are turned
on iUf:, fild jus ater dark Uhe moths carn be seen in flight, alighting
hee .e u to : {. T ~he moths are shor t-lived and feed
only < : 'cr 01 e The s-asonal history of th pale western


) ~
' 1' ~


r oose sonil nanldavo. i oistue whenever pos-
P1r < l bo thir survival, whereas excess moisture
e worms is con~ducive to the spread of a
b E noesive moisture in the soil
evere they aire subject to attack by



Several successive dry spriigs 1 o I
the pale western cutworm populatici t outbreak pro io t- a vet
spring as a rule tends to reduce heir nulides to po aq-
preciable damage occurs the following y a"


Observations made during rece ye indicate h e uat and
spring barley are the principal cro1 -i. I (c Pa
region. In rare instances newly seeded j ji > ......
Row cops planted before June 10, on roun hoe the x:. K 1
or barley, are also subject to atk a aciv wor e L e
seeding time.


Cultural Pactice

Extensive field observationsnhave ...icat d ce a a -
ment practices are of definite 'ae in pr0\ Liog inj ay < Lhe tale western

First, wheat sown in the fall on I Aliih has bee- cianiy allowed
during the preceding summer, and which had been planted t e preceding
year to a row crop such as sorghu, aloe t without excep escaped
serious injury, notwithstanding some :-trgioal camage ,'h. s eh fields
bordered infested wheat-stubble land.

Second, alternate wheat culu e a suan(! umer fallow "t.... be an.
effective means of reducing the chances n osr injury In ppl 'ing this
method, the stubble after 1 year 's crop J1 left un'isturbed ui thle follow-
ing spring, when the ground is cultivateQ, and kcpt lean th',oughoc the sum-
mer unil wheat-seeding time, The spring cu'ivation should star as early
as possible without incurring dn of spring soil blo' *i g, prefeably be-
fore April 15. With but few exceptions, wheat grown in this :ner has es-
caped severe injury. It should be noteJ that wheat on -t .r-ifa!ow ground
in which insufficient moisture has been stoed during t', li period, or
which supported any weed growth during the eg-laying perri of the moths,
was subject to attack during periods of h heavy genera] i-fl1 io2 I should
also be noted that the practice of ol a surer faloxing to years
is recommended for the purpose of nih' i i ,g h ei~ec o : As of the
pale western cutworm. From the strp of soil con env' a C e.
cultivation Tay be more desirable than clea alloi, but a ctiveness
as a substitute for clean fallow in controlling the palke wetr cutworm
has not been determined.

A control measure developed by H, L, S uans of the ia Depart-
ment of Agriculture, and found effect ive in toutbern Ale a ed on the
starvation of the newly hatched ;orus; This i accopl i by thorough
cultivation of the stubble fields to destroy all green veget i early in
the spring as soon as the weeds and volunteer 0iaio show ( to 2 inches of
growth above ground, followed by a delay of 10 days before dia to a spring
grain crop. In the southern Great Plains, ho, ever, where faLi-sn vheat is
the chief crop, the starvation method of control vould not ee (Ap,.lIcable un-
less the seeding of a spring grain crop, such as barley, on wheat-stubble


land could be deay e until the starvation of the young cutworms is ac-
comrplished. The method is believed not to be generally applicable in this
area for the reasons t (1) the hatching period of the pale western cut-
worm overlaps the seedeig date of spring barley and (2) the starvation kill
would have to apprc h perection because a cutworm population which would
not. re ll- stablished winter wheat plants would be highly
destructive to youg "- e barley plants. However, this .ethod of con-
trol has not bee, tr of the southern Great Plains, and is mentioned hero
because circumstance ay arise which might warrant giving it a trial.

Uti t i o La .d cn Which the Crop Has Been Destroycd

Once a ec e ppulaton of the cutworms has become established
in a field, it ,c r nuintain i s-lf until starved out or until cli-
matic corIitons are unfavorable to it. Consequently, land on
which ,h-at or so e e small-grain crop has been destroyed by the cut-
worms in the srli 1 Nh< !d ot be returned to wheat the following fall. Many
iusta:ce have .... during the present outbreak whore the continu-
ous planting of .'-1- reuied in the loss of three consecutive wheat
crops .heat o e e into whcat-stubble land is almost certain
to be royed u. cr ou k condition s

.- eor A cih a crop v,as destroyed in the spring may be
planted to rov: + aety, provided the seeding of the row crop is
delayed until t ei of the cutworms is past. Ordinarily, row
crops ca be pi-. e ly ucder th above conditions by delaying seeding
until 0 e 1. .eins, ocver, cutworm development is delayed,
and in -erthe: u- lively feeino worms have been fou d as late as
June 25 fee u. l e e cied by a careful cxaiination of the
if Lie~rvs found are in their cells or have passed
into e pale t ne screr stage, no further daage will occur.

Use tro, W r as a !f.,eans of Protecting Crops

an adj
the advao ofQ C' K.v

contisuous hcav y if

e -adiug the margin of a noninfesed field from
urrow barriers are of some alcue in stopping
Cosidrable success was obtained in western
t) Vunrey oi fallow ground from invasion by list-
le p furrows between the crop to be protected and
i oIs


Ihe cropj

O-I, tu .1 :;
i tl tile( re ]} io] i

K .,utw > r geerally distri'utcd in a field
Ie t~a I an be done to prevent det ruction of

POisoned Bran Bait

,, : : ~o 'he wormsi with poisoned bran bait spread
e roun with a wheat drill. hive generally
.o Iii suich a small porcntCge of kill that
a (c so~i( ot wa rriant the expense of baiting.


Use of Lights to Attract the ,Ioths

At night te moths are rather DtrongJy dttactcd to Ihi
habit suggested the poss ability of rapping the moths s c f
ing the number of egg-depositing feiraiCs. However, urjt' ., o o
work with light traps in the area it was found that o1y 18 c r ic
adults captured were females, and the irjority of hes h I
their full complement of eggs before capture. Furthemore,,
operating a sufficient number of light traps would be prohibi'n


There re nzany diff erent specJe of cu',oCm i1
region. Wthen outworms are found in -rop or t: t~re J<
important to hnow che identity of the species involved '.
worms can be 1,ccs 1 oly combated with poisoned brin, Li e
cutworm is the notable exception in the Great Plai> .eg i.
habit of subterranean feeding.

1 i)H~~KJ.. ';
t i v~,2J
C, th.... (X.

'I ~'1 )

Specimens of cutworms should be submitted to the !ea cc nt agent
who will have them'I identified by some qualified person,
cannot be recommended until the species is known.







A dult

SoDt. Oct. Nov. Doc. Jan. Ieb. Mar. Apr. May June l Au, t Oct.

3ft&are 1.-- Seasonal history of the pale western cutworm.


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