Judith Gap journal. [volume] (Judith Gap, Mont.) 1908-19??, 1910-12-09
Army Cutworm as a
Pest Of Winter Wheat.
BY r. A. Cooley, Montana State
EntomoloQist.


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As it's name suggests the insect is a
cutworm which appears in large num-
bers. 1t is very general feeder, re-
fusing to eat practically none of our
garden plants and field crops, but is
OF more Importance as pest of grain
than in any other role
The destruction to grain wrought by
an outbreak in the Gallatin valley in
1907 was remarkable. Four thousand
i've hundred and sixty-two acres were
reported to US by letter as being more
or less affected. Two thousand six
hundred and ten acres were reported
as being completely destroyed so that
re-seeding was necessary. 1t was
prefectly clear, however. that our in
formation covered only part of the
affected territory and the total injury
done was greater than above indicated.
The larvae appeared in incredible
numbers and completely deyoured
every green thing. At other times and
in other places it has since been very
destructive.
Early in the spring, with the first
warm days, or about the time the first
vegetation starts, these cutworms may
be found in fields Of winter wheat hid.
den among the stools of grain. They
eat holes in the leaves or when abuu.
dant devOur the whole leaves, and
even whole stools of grain may be no
ticeably injured. AS the season ad.
Vances they become larger and require
more food and it is ordinarily at this
time that the farmer first notices their
presence and becomes alarmed. The
insects nave the characteristic cut
worm appearance. They are hairless.
and dark gray in color, fairly marked
With longitudinal stripes. Their great.
est injury is apparent about the first
to the tenth Of May, and at about this
time they begin to disappear into the
earth for pupation. They dig down
about three or four inches and con.
struct oval cavities in the soil and
transform to the pupa stage. In July
or early August the adult insects or
moths emerge from these oval cells
and after flying about for time de.
post eggs for the next generation.
These eggs hatch in the fall into very
minute, almost black caterpillars, or
worms, which are not readily rec0g.
mzed as the same as those found in
the spring. They feed on the various
plants OF their choice until cold
weather sets in when they become
torpid and remain inactive until the
return of spring. Ordinarily they
reach the length OF about one.half inch
before winter. They are not usually
found by the farmer until the spring
OF the year. though in a, few instances
they have been reported in the fall
when prolonged warm weather had en-
abled them to feed we'll into Novem-
Der until they had reached consider
able size and We're eating a noticeable
amount
Farther south, in Colorado this in
sect is believed to be double brooded
though it passes the winter in the
same condition as in Montana. In
Colorado it is believed to pass through
another complete life cycle during the
summer months. reaching the same
tana form attains before the coming
OF winter.
1t is probable that this insect is al
so injurious to alfalfa and it migrates
at times into sugar beet fields. There
are few cases on record of it's hay
ing been very injurious to this crop
It is native species and before the
coming OF man doubtless fed on vari-
Gus wild plants and these wild plants
continue to constitute part of its
food.
It is quite noticeable that this cut
worm usually appears generally dis
tributed throughout the grain field. in
dlcating that the parent moths scat
tered their eggs about through the
Held. Such moths do not lay their
eggs on the bare soil, but deposit
them on or near plants that will con-
stitute suitable food for the young.
1t follows then that it is quite desir.
able to keep fallow fields free OF vol
untary grain and weeds in regions
where there is reason to fear this in
Sect. Frequent stirring of the soil for
the purpose OF killing the weeds and
conserving the moisture is therefore
In harmony with the right practice for
the control of this insect.
Our experience at the Experiment
Station, and inquiries among farmers,
have indicated quite clearly that in
regions where this cutworm is liable
to be destructive it is we'll to practice
carly sowing. This results in larger