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MICROCOPY RESOLUTION TEST CHART

(ANSI and ISO TEST CHART No, 21

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^ APPLIED INA/1GE Inc

16^^ Eas! MO'H Strt-gt
f^ocf^este'. New York 14609

(7' 6) 482 - 0300 - Phone
(716) 288 - 5989 - fa»

CIRCULAR No 26

Printed by the order of the Legislature.)
PROVINCE OF NOVA SCOTIA.

COLLEGE OF AGRICULTURE

Truro, N. S., December, 1917

TWO IMPORTANT VEGETABLE PESTS

BY

W. H. BRITTAIN

Provincial Entomologist.

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THE

IM^A'l'K I.

POTATO STEM BORER. i....i.M,a nii.Mda K^.

pm; ir.FPrt. sinK''' e(!i< greatlv rnlargtrt. 2. Rhubarb stem show
inc ontranrp holi" nf ratprpillar lunr Krounrl. ■'>. Rhubarb Ftpm showinRhorinRS
Fully Ernviii caterpillar I'lilarnpd about tw<i liirips. •>. I>upa
I tiiiii.-. li. \ilull itilari;ccl ul.ijut two time.-.

I. Eggs in place on 'itrr

i*f catt'rpithir. 1.
irilar(;(d : biiu! 1 v.i

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TWO IMPORTANT VEGETABLE PESTS.

BY W. H. BRITTAIN

PROVINCIAL ENTOMOLOtilST.

The Potato Stem Borer iGortyna mlcacea Esp.)

Durinji the past summer numerous c-omplaints have
been heard concerninj; the (himajie to potatoes, corn? rhu-
barb, etc. by a borinp caterpillar and articles on this "new
potato pest" received wide circulation in the local press.
The culprit responsible was described as a naked caterpillar,
about an inch and three eijihths lonj; when full yrown, with
a shiny chestnut-brown head, pinkish or jireyish-pink back,
pale at the joints of the body and with under surface and
legs lighter in color. This is not a new pest as many sup-
pose, though it undoubtedly has been unusually common
during the past summer, possibly due to the fact that so
many new back yard gardens were planted on waste land
that had formerly been overgrown with weeds. The insect
is an emigrant from Europe and gained a foothold in Can-
ada several years ago. It has been under observation at
the Agricultural College for the i)ast three years. It is
called the potato stem borer because the potato is one of its
favorite food plants.

Food Plants.

We have found the in.sect attacking not only the i)otato,
but also corn, rhubarb and sugar beets and very likely it
will be to infest other garden crops. It has been recorded

I'lsewhtTc as fwditiK on docks, horsetails, .siuIki's and other
plants, so evidently it is a very j^eneral feeder. We
have never known it to attack turnips, cahhajfes, cauliflowers
carrots or parsnips even when neij^hhorinx crops suffered
severely.

Infuries.

The principal damage has been done to potatoes, though
local outbreaks of more or less severity have been recorded
to rhubarb and corn. The insect enters the stalk at the
surface of the ground and bores upward through the centre.
The first symptom noticed is the wilting of the plant, u.sually
followed by the collapse of the stalk. In the case of rhu-
barb the insect generally bores through and through the
crown as well as in the stalk and this results in the gradual
wilting and death of the part above ground.

Life History.

The eggs are laid by the female moth during the latter
part of August and September. They are doubtle.ss de-
posited on various weeds, though we have only found them
on couch grass. They are very small pinkish colored eggs,
faintly ribbed and are laid loosely, sometimes in rather large
numbers, on the stems partially surrounded by the leaf
sheath. The larvae hatch in June and make their way
to a suitable food plant where they bore a tiny en-
trance hole in the stem, usually at the surface of the ground.
They bore in the stem or in the crown of the plant until
.some time in August and then enter the ground where they
transform to a pupa, emerging in late August or September
as an adult moth.

Control.

Control mea.sures may be summarized as follows:

1. Carefully destroy all weeds during the latter pari

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of AuKust and Septi'mbt-r. when the moth is depositing her
eKK-s. This is particularly im[)orlant in the case of a
permanent plantation like rhubarb.

2. (hardens should not be planted on waste land that
has been allowed to ^row to weeds the previous year. Such
land should be plowed and cultivated the autumn previous
to plantinK

:{. Rotation of cro|)s is beneficial when the insect has
gained a foothold in a plantation, e. j?. follow potatoes with
turnips, cabbage, etc., that are not subject to attack.

4. As the in.sect is chiefly a garden pest, pickinK th<
injured stalks and destroying the caterpillars is practicable
and should always be done to |)revent outbreaks in future
.seasons.

The Zebra Caterpillar iCeramlca plcta Harr.)

A yellow and black striped naked caterpillar has re-
cently been doinj? considerable damage in certain parts of
the province, stripping whole fields of turnips of their leave.s
and al.so feeding on potatoes, beets, mangolds, beans, peas
and even apple and other plants. This insect is known as
the zebra caterpillar and unlike the potato stem borer is a
native insect. It is a periodic pest ancJ only rarely occurs
in destructive numbers.

Life History and Habits.

There are two broods of the zebra caterpili. ne feed
ing in the early part of the summer the oth»" * ■ late
summer and fall, the second brood being the n - -iic-
tive. The eggs are laid in flat masses on the le. var-
ious plants, those of the first brood hatching durii.. ne lat-
ter part of June or early in July and those of the '-ond.

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fluririK the latter j)art of VuKust. The larvae of the first
brood feed for about six weeks. th«'n ent.-r thcKround, where
they remain for two or three weeks, when they emerKe as
moths to lay the ckk-s for llie next brood, individuals of
the second broojl may be found feedinw from late AuKust up
until freezing weather. The winter is pa.s.sed in the pui)al
stale.

Control

On a small .scale and where cheap labor is available,
hand-picking and destroying the leaves l)earinK e^Ks or
newly hat.'hed caterpillars, is the most practicable method
of control. Over lar^e areas, dusting with powdered arsen-
icals, e.K. arsenate of lime, arsenate of lead. I'aris ^reen
etc.. diluted with H to 10 parts ot hydrated lime, applied
with a powder j^un or blower, will prove more satisfactory.
Treatment must be wiven early, since when half Krown or
more the in.sects are too diHicult to kill.

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