The cabbage-root maggot (Phorbia brassicæ Bouche) [microform]

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A /APPLIED ItVHGE I

^K '653 East Main Street

y.g Rochester. New York 14609 tjSA

^S (716) 482 - 0300 - Phone

^= '716) 28a - 5989 - Fax

CIRCULAII No. sa

Sj

PROVINCE OP BRITISH COLUMBIA.

DEPARTMENT OF AGRICULTURE

(HoBTICfLTl'BAL BRANCH).

THE CABBAGE-ROOT MAGGOT

(Phorbia brassictc Bouche).

1HERE are few insects attacking vegetables which cause greater
loss and disappointment than the one which as a small white
naggot is often found infesting the roots of cabbages, cauliflowers,
ape, turnips, and radishes.

During early spring and summer, in the seed-bed and in the

ermanent plantation, the leaves of certain cabbage and cauliflower

plants frequently turn yellow, wilt, and droop. If an examination is

Mkle.

Female.

Tbe adalt fliei.

(After Olbs and Treherne, Ent. Branch Bull. 12, Dom.
De^.. Agrlc, Ottawa.)

ide of the roots a number of maggots, varying in size but attaining

^e length of '/^ inch will be found embedded beneath a slimy mass

decaying vegetation and soil. With radishes and turnips similar

white maggots will be found in burrows or galleries in the edible

portion of t'e roots.

The adults which produce these maggots arc small fljes, resemWmg
the ordinary house-fly in general appearance, but more slender and
slightly smaller. They are represented above. They appear on the
wing in very early spring, having developed from over-wmtermg
puparia in the soil. They lay eggs on or near the crown of the
plant on the level of the soil surface, as shown in the accompanymg
illustration.

Where the ecn are laid. (After Gibaon and Treherne,
bS' BrtiJ^lf^Bvill. J J. Dim. Dept. Aifrlc. Ottawa.)

These eggs hatch in five to seven days into small larvae or n.
which penerate the soil and attach themselves to the roots ot the
plant. Here the larvae remain feeding and destroying the roots for
from nineteen to thirty-two days.

It must be understood that all of the adult flies do not emerge from
the soil in the spring at the same time. The process of emergence
may be continued for over a month. .A.s each female emerges she
mates and proceeds at once to lay eggs. Thus we find a continuou>
and overlapping series of stages in existence. It may be possible, it
can be seen, for the larva, which have developed from flies whicl
emerged the earliest, to be nearly mature at the time the latest flie^
are emerging from the soil. This complex and difficult situatioi
proceeds, throughout the year, and results in the fact that some egg

are being laid every day from April until September. This point
must be clearly borne in mind, as upon it is based one of the essential
features of satisfactory control.

When the larvae become full-y. » they form what are known .''s
.puparia. a stage in their life-history which corresponds to the

Whero the magKOta teeA and the type of
Injury thev cauiie. (After Olbson ami Treherne,
Knt. Branch Bull. 12, Dom. Kept. Agrlc.
Ottawa.)

chrysalis of a butterfly. The puparia of this fly resemble grains of
wheat in size and colour, and may be found in decaying roots or in
the soil adjacent to infested plants. From two to three weeks are
passed in this stage during the summer months, but towards autumn
the stage is lengthened out and the winter is passed in this form. The
puparium stage is merely a resting stage from which eventually the
adult flies emerge, and, as can be realized, this emergence of adults
may be more or less a continuous process throughout the summer
months.

a

■'.Si

- ', f=

Familial MMmrw.

from gaining accw. to the olants Rr-«. V 5 **'"'* ^'"

.houIdT frown under .u^r "'""L' *"'*"^'^ '°' ^^'^ »*"«
Cabbage, anrjuliflot" sZl ^ ^iStd ^'' TT
firit month under this protection aJi ^m-" / *^°*" ''"' ^
some such screen fo, in thu ^" ',""''• '^^'1"» »houW possess

from the ob„"xl'^:„ll':f;'/^ -y .»- Ifuaranteed free

unpleasant to eat Cabt^es fu th- " ""- ' '^'°^" ''^•' "^

» W^H--

cond,.,o„. Th. piece of ^„„d defined fo.r;:rar„r«°?j:^j

plantation should be thoroughly cultivated during thta week and
finished off with a light roller and harrows. It is essential that the
surface of the soil be sunrnth and not lumpy.

One-ply Felt Tar-paper Disks.— hi the plants are removed from
the seed-bed and set in the permanent plantation a disk of one-ply
felt tar-paper «hi »jld be placed around the crown of the plant, flush
to the soil. The illustration on the preceding page indicates the correct
procedure.

These disks may be circular, square, or hexagonal in shape, approxi-
mately 3 inches in diameter, with a slit to the centre, whici. enables
it to be quickly arranged by the planter. If nothing better than
ordinary tar-pap jr -an be obtained, two disks to a plant may be

riant protected by tarred-paper dl«k. (After Rrltton and
Lowry. Connecticut, 190.)

necessary, i elt tar-paper does not curl from the heat of the sun and
is therefore prefera' le. The idea of these disks is partly to detract
the fly by the odou: of tar, and partly, if eggs are laid, to guide the
young larvae away from the root system. It is essential that the
disks lie flush to the ground-level, otherwise the adult flies may crawl

benetth them and depcwt egg.. The virtue of havii* ■ nnooth

t^So t^!;S" H '":""' f^'*^" «r.n.pl.„ti„g. there i. J^MHy

^IhITh r """ 'r ^'^ ^^'^ °' •"• Thi. method i.
recommended for commercial plantatbni.

ff'^rW.V W'^wA'-i-If the Ur-|*prr di.ki arc not used, applications
of hquid. should be applied to the root., once a week. The ob^t ^
the^ apphcatKin. » to destroy the young maggots l-fure thirca,
destroy the plant. It will be recalled that egg-lfying is J^re or les
. contmuous proce.,s during the summer anTthat the e^ hatch"

Sl^ .n f L!"^ "' ""''" '° "^' «»"''" °' *«'" «^e effect ve.
Ddution, of carbohc-acid or kerosene emulsions may also be app ied
These solutions have been found of special value in gardens. Under
field^cond.t.ons they are not practicable, chiefly on Scount of their

flow:r:Ts''ad'l'nr'^h" ' '•' '"^'"^ °^' ^^""'"^ '^''''»-«" -d -"«-

nowers IS adopt.,! by many growers to ensure carliness the following
year and ,s mtended that the plants should be able better to coZ!

tlluT. °' r ^'-'"«««"»» ^y 'he mere fact that the plants a ewd
estabhshed m the sprmg. Growers who follow this method wouldT.
well advsed to seed a few radishes early i„ the spring in the oZ ne^
by. to attract the adult females and thus to act L tfaps. Ex^^Jience
has shown that the success of these autumn-planted cabCs il
altogether dependent on the number of flies present in the Spring and
oTl^l P'ants available on which they are able to dej^si*';^
Other Remedial Measures.-Thtrc is possibly no insect affecSmr
P.rden produce that has been the subject of more conflic^g :vide"cf
m Che matter of control than the cabbage-root maggot Eve^

^t7Jr VT'"' "'r ■"^"' °' ^^"^'^^•°" '» combatTe mag^;^
of mer? These applications frequently take the form of solu^ns

tZuT' . ?l!" '°'''''' "^•■*^^'' °'- P^'*"' «>'"tions bought
through local supply-houses. Soot, wood-ashes, tobacco powder, lime

their n' I '''"'" ^''? '^''' ^^P"^^ ^^^^ ^^^ °''^" --^» * tnlg
on a Z f''^'"'"''^ '''^" '"^^"^^"'- There is no reason whv

on a garden scale any mixture properly and frequently applied should

insecticidalv.'' In a commercial way and under prooer control

Further information regarding the habits and control of the

lo^crBrnch'T -'' n °''""'' '^^ ^""^*'" ^^ ''' ^ntomo-
Jogical Branch. Dommion Department of Agriculture, Ottawa.

Victoria, B.C.. issued March, ipi8.

6

ThJ« cifcuhr ha» htm prc|>Brcfl by k. C. Trcherne. Field Officer for
Brilitb Columbia, Kntomnlngical Hianrh. T)ominion Dcpartmrnt o( Agri-
culture, at the rrqueit nf the liorticultural Branch.

I'tipie* of thi« circular may be obtained free of charge on application
to the Hnrticult-iral Branch, Detiariment of Agriculture. V iitona. B.C..
or from local branch oAicet of tne Department.

9<

VICTOBIA. B.C. :
I'rtnird hy Wii.imm II. n ixix, I>rliii»r li. ilir Klug'a M<mI Exivllmt Majvuty.

lOlS.

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