an

‘
a

a

Historic, archived document

Do not assume content reflects current
scientific knowledge, policies, or practices.

iit sy awe ave

OF THE

U. S. Department of Agriculture &

Class 22 = | Bone take

ac ancia
4) ;

a

CIRCULAR NO. 63, SECOND EDITION.

United States Department of Peeienititie

BUREAU OF ENTOMOLOGY,
1 0. HOWARD, Entomologist.
as 11 SG Begartme!

eF "

ROOT-MAGGOTS AND HOW TO CONTROL THEM.

By F. H. CHITTENDEN,
In Charge of Breeding Experiments.

The roots of vegetable crop plants of many kinds are subject to the
destructive influence of maggots which injure them severely during
certain seasons. Several forms of injurious root-maggots are recognized,
but of these there are three species which are much more destructive
than the others. The most important are the cabbage maggot and the
imported onion maggot, the former a specific enemy of cabbage and

a ry
ae 3
FAL Lp NS EY 0

aT: : \ or
Gaxcasiae \
ry ee in nes ha sca ia

eke H i

G f i ee

ad

Fia. 1.—Seed-corn maggot (Pegomya fusciceps): a, male fly, dorsal view; b, female, lateral view ;
c, head of female from above; d, larva, from side; e, anal segment of larva; f, anal spiracles;
g, cephalic spiracles; h, puparium—all much enlarged (author’s illustration).

other cole crops, the latter of the onion. <A third species, the seed-corn

maggot, attacks the sprouting seeds of both onion and cole crops and of

a considerable variety of other plants, afterwards working into the roots

and stalks beneath the earth’s surface. As the last-mentioned insect is

nearly omnipresent and omnivorous, it will receive first consideration.
These species all belong to the genus Pegomya (Phorbia) of the dipter-
ous family Anthomylide.
THE SEED-CORN MAGGOT.
(Pegomya fusciceps Zett. )

Vegetable growers frequently find that planted seed fails to develop,
and, on looking for the cause, discover a small white maggot which, from
early-observed occurrence on seed corn, has been termed the seed-corn
maggot. In more recent years it has often been associated with injury
to beans, whence another name, © bean fly.”’ Many other vegetables

2

are subject to damage, cabbage, turnip, radish, peas, onions, beets, and
seed potatoes being often much affected. This insect, which is generally
distributed in the United States, is shown in its different stages in figure 1.
It resembles the common house fly. The particularly distinguishing
characteristic of the fly is a row of short bristly hairs of nearly equal length
on the inside of the posterior tibiz or shanks of the male (fig. 1, a).
The length of the wing is about one-fifth and of the body about one-
sixth of an inch. There is little doubt that the insect is of European
origin and that it is increasing in destructiveness in this country.!

In its earlier stages, also, the seed-corn maggot resembles the house
fly. The maggot is footless and cylindrical, presenting in profile the
appearance represented at d. It measures about one-fourth inch in
length and about 0.04 inch in width. The -color varies from nearly
white to pale yellowish.” The maggot transforms into a puparium (h),
barrel-shaped, of elliptical outline, and pale brown in color, measuring
about 0.15 inch in length and 0.05 inch in diameter.

Indications are that there are several generations of this species
annually, one developing in the North in June from seedlings, and later
ones from roots, dead or dying plants, and other refuse.?

METHODS OF CONTROL.

Owing to the difficulty of destroying root-maggots and other subter-
ranean pests and the cost of chemicals for the purpose, growers depend
largely upon methods of prevention. To be thoroughly effective these
methods should be employed before the insect’s eggs are laid.

Sand and kerosene.—A common method for deterring the parent flies
from depositing their eggs consists in placing sand soaked in kerosene—
a cupful to a bucket of dry sand—at the base of the plants, along the
rows. This mixture will also kill young maggots that might attempt to
work through it.

Carbolic-acid emulsion.—For all three forms of root-maggots which
we are considering, a carbolized form of kerosene emulsion is effective.
This is prepared by adding to 1 pound of soap boiled in 1 gallon of
water, one-half gallon of crude carbolic acid, and diluting the whole
with from 35 to 50 parts of water.t.| This mixture is applied about the
stalks of the plants affected. It is best to use it a day or two after the
plants are up, or are transplanted, and repeat every week or ten days
until about the third week in May, in the North. Farther south these
applications must be made earlier in the season.

14 more extended notice is furnished in Bul. 33, n. s., Div. Ent., pp. 84-92.

2—In all material examined there are only 6 or 7 cephalic spiracles (fig. 1, g),
whereas in the other root-maggots here considered there are 11 or more.

‘There is evidence that another maggot has been confused with this species.

‘The mixture is effected according to directions furnished in Farmers’ Bulletin
127, p. 22 (1903 ed.), which will be furnished on application.

5)

The use of mineral fertilizers.—Mineral fertilizers are useful as deter- -
rents, particularly when employed just before or after a shower has
thoroughly wet the ground. The principal fertilizers for this purpose are
kainit, nitrate of soda, and sulphate or chlorid of potash. They may be
used as top dressings before planting; or, if not employed until after-
wards, they should be applied as nearly as possible to the roots, the
earth being turned away from the plants for this purpose. These ferti-
lizers possess the advantage of acting also as a stimulant to plant
growth, thereby facilitating recuperation from root-maggot attack.

Danger from use of organic fertilizers.—Stable manure and organic
fertilizers are apt to induce infestation, since the species under consider-
ation is well known to develop in excrement and other decomposing
material. Numerous instances of this have come to the writer’s knowl-
edge during recent years. It is advisable, therefore, to avoid the use of
manure, rotted leaves, or other organic fertilizers, and to avoid planting
in fields in which there have been infested or diseased plants.

Hand methods.—As soon as seed fails to appear at the proper time or
the plants show signs of wilting and maggots are found to be present,
the seed may be hoed out or the injured plants pulled and destroyed,
together with the young maggots.

Most of the methods mentioned above have been used with success
against onion maggots and other root-feeding species, and are all that
is required in many cases of ordinary infestation of vegetable roots.

THE CABBAGE MAGGOT.

(Pegomya brassicae Bouché. )

Cabbage and related cruciferous crop plants frequently suffer severe
injury from the attack of the cabbage maggot. Young plants are most
seriously affected, the maggots eroding the outer surface and boring
into the interior of the roots, devouring the tender rootlets and
frequently penetrating into the lower porticn of the stalk.

This insect, known also as the radish maggot, is an imported pest,
and was first noticed ruining cabbage, cauliflower, and similar plants in
New York State about half a century ago. It does most serious injury
throughout the northern tier of States and Canada, attacking all forms
of crucifers, whether wild or cultivated. In that region it is the cause
of more or less loss to these crops year after year, but as with other
destructive insects, it is much more abundant in some seasons than in
others. Since 1902 it has not only been exceedingly destructive, but

‘It is frequently necessary to use these fertilizers in large quantities. In cab-
bage fields a fertilizer of the proper composition is applied before planting at the
rate of 1,000 to 1,500 pounds to an acre. After the plants have started growth,
a top dressing of 100 pounds of nitrate of soda and 200 pounds superphosphate
is added. When the heads are beginning to develop, a third application of
about 200 pourfds of nitrate of soda to the acre is often desirable. For details
consult Voorhees’s ‘‘ Fertilizers.’’

“

has increased in injuriousness from year to year. Frequently entire
crops over considerable areas are completely destroyed.

Two or three generations of this maggot are indicated in the Northern ©
States, and perhaps four or five in the South.

METHODS OF CONTROL.

Since this species also is a root-feeder, the remedies prescribed for the
seed-corn maggot are applicable. In addition there are certain prevent-
ive and other measures for its destruction that have been found succegs-
ful, their use being justified by the great value of cabbage plants.

Carbolic-acid emulsion, prepared as prescribed on page 2, and diluted
about 35 times, is particularly applicable when this maggot occurs on
radish and other plants than cabbage and cauliflower.

Hand picking, although laborious, has the merit of being effective,
and is practiced with considerable success by extensive cabbage grow-
ers, although not practicable on radish and similar crops. It consists
in pulling up the young cabbage or cauliflower plants, examining the
roots for eggs and maggots, and either destroying the eggs and maggots
by crushing with the hand or by washing the roots in a strong solution of
soap and then replanting. In most cases the plants show no ill effects
from this treatment after two or three weeks have elapsed. By looking
closely, the minute white eggs may be seen about the stalks of young
cabbages, and if the earth be raked away so as to expose the eggs to
the sun these will dry up, thus preventing the maggots from hatching.
Afterwards the plants should be hilled.

Methods of cultivation.—Experience shows that comparatively little
is to be expected from various farming methods which are sometimes
perfect safegards against other insects. Whatever might be advised and
found successful on one farm might, for one or more reasons, be found
ineffective on another.

By keeping the soil well hilled around the plants the cabbage develops
more roots, thus affording more food for the maggots and still leaving
enough roots to strengthen the plant itself.

Crop rotation should be followed with any plants other than crucifers
or onions. With these latter it is inadvisable, as the same atmospheric
or other conditions which induce injury by the cabbage maggot seem to
operate in increasing the numbers of the onion pest, which has a similar
distribution.

Fall plowing is advisable.

Crop remnants of all crucifers, and particularly cabbage stumps, should
be removed and destroyed, especially early in the season. Late in the
fall a less number of maggots would be destroyed in this way, but it is
always a desirable method for the protection of the crop against other
pests which harbor in the old stalks or feed on the new leaves in early
winter, to appear the next spring.

5

Gas lime, applied about each plant, has often been advised as a
remedy, but those who have tried it are almost equally divided as to its
efficacy. It is well worth further experiment where the gas lime can
be obtained fresh without difficulty. It may frequently be had for the
cost of carting.

The bisulphid of carbon treatment.—In case tarred paper cards, which
will presently be described, or other preventive methods here given, are
not employed, and the insects occur in great numbers at the roots of
cabbage, bisulphid of carbon may be used. It should be applied below
the root system with a special injector or syringe,’ taking care that the
application is not made di-
rectly to the plants, as it is
very likely to kill them. A
hole is made a little distance
(8 or 4 inches) from the
plant, and the injector in-
serted at an angle, as shown
in fig. 2. After injecting the
liquid the instrument should
be withdrawn and the hole
closed by packing it down
with the foot. From a tea-
spoontul to a tablespoonful to
each young plant, and a sin-
gle application, is generally
sufficient. ‘ |

Tarred paper cards.—The _
use of disks or pads of tarred peas Fes
paper for the protection of
cabbage against the oviposition of the fly was perfected in 1889 by Mr.
W. H. Goff, who describes his cards and the manner of cutting them as
follows:

LP

NL!

Frag. 2.—Bisulphid of carbon injector in use.

The cards are cut in a hexagonal form (fig. 3), in order to better economize
the material, and a thinner grade of tarred paper than the ordinary roofing felt
is used, as it is not only cheaper, but being more flexible, the cards made from
it are more readily placed about the plant without being torn.

The blade of the tool, which should be made by an expert blacksmith, is
formed from a band of steel, bent in the form of a half hexagon, and then taking
an acute angle, reaches nearly to the center, as shown in fig. 5. The part mak-
ing the star-shaped cut is formed from a separate piece of steel, so attached to
the handle as to make a close joint with the blade. The latter is beveled from
the outside all around, so that by removing the part making the star-shaped cut
the edge may be ground on a grindstone. It is important that the angles in the
blade be made perfect, and that its outline represent an exact half hexagon.

1 What is known as the McGowen injector, formerly manufactured at Ithaca,
N. Y., but no longer for sale, has proved most successful.

6

To use the tool, place the tarred paper on the end of a section of a log or
piece of timber and first cut the lower edge into notches, as indicated in fig. 4,
using only one angle of the tool. Then commence at the left side, and place the
blade as indicated by the dotted lines, and strike at the end of the handle with |
a light mallet, and a complete card is made. Continue in this manner across
the paper. The first cut of every alternate course will make an imperfect card,
and the last cut in any course may be imperfect, but the other cuts will make
perfect cards if the tool is correctly made and properly used.

The cards should be placed about the plants at the time of transplanting. To
place the card, bend it slightly, to open the slit, then slip it on the center, the
stem entering the slit, after which spread the card out flat, and press the points
formed by the star-shaped cut snugly
around the stem.

A Wisconsin grower protected 7,000
plants and secured a splendid crop, while
unprotected plants nearby would have
been a complete failure if the maggots
had not been picked off by hand. Others
have reported similar success. One re-
ported having lost only 25 plants out of
10,000 to 15,000 that he protected with
the cards, where ordinarily he would
have lost from 75 to 90° per cent of the
crop.

Fia@. 3.—Tarred paper card in

outline, one-half size (after
ee? The tarred cards are applicable to
cabbage and cauliflower only, but it is claimed by those
who have employed them
that they are cheaper,
more practicable, and
more efficient than any-
thing else yet devised for

; for cutting

preventing the ravages of cards, about
Fig. 4.—Showing how tool is used, dotted line the cabbage maggot. ca tee

indicating position of edge of tool (after Success in using them is Goff).

poe dependent upon their be-
ing properly applied, to fit tightly, so that the fly is unable to obtain
access to the stem for the deposition of her eggs. Cards must be re-
newed and their use continued for each maggot year to be effective.!

‘
eecee w

Fie. 5.—Tool

THE IMPORTED ONION MAGGOT.
(Pegomya cepetorum Meade. )?

Coe ° . . °
The name “imported onion maggot’’ is used for this insect because
there are other onion-feeding maggots in addition to the seed-corn

1A Wisconsin firm has used as many as 20,000 of these cards a year, and esti-
mates the cost of material and labor at about $1 for the protection of 1,000
plants. This shows its practicability on a large scale.

2 This species is commonly referred to in literature as Anthomyia and Phorbia
ceparum Bouché. According to Mr. Coquillett, it is difficult to decide, from the
description of the adults, whether or not Bouché’s and Meade’s species are
identical.

a

maggot. Its injury, which constitutes the most important drawback to
the culture of onions, is accomplished by the consumption of the bulb,
inducing subsequent decay of the affected portions and their very fre-
quent destruction.

The fly and the maggot resemble preceding species, although their
average size 1s a little larger. The length of the fly’s body is about
three-sixteenths and the wing expanse nearly three-eighths of an inch.
The male is gray with black bristles and hairs; it has a white face with
black hairs, and there are three dark lines on the body between the wings
and a row of black spots on the abdomen. The female is a little the
larger, and inclined to dark yellowish, with a pale yellowish face.

As in the case of the cabbage maggot, two or three generations are
evidently the rule in the North.

REMEDIES.

The methods of control prescribed for the seed-corn maggot are fre-
quently about all that are necessary for this species. In case of severe
infestation the bisulphid of carbon treatment, discussed on page 5, as
also other remedies advised for the cabbage maggot, are useful, with
the exception of the tarred cards, which can not be conveniently nor
economically used on onion. The flies are probably attracted to old
onion beds and to crop remnants; hence clean field methods are
advisable.

Nore.—This circular has been prepared to facilitate correspondence,
due to the fact that the three root-maggots mentioned herein have been
extremely injurious during recent years. A monographic account, which
has been of service in the preparation of this circular, was published in

1894 by Prof. M. V. Slingerland (Bul. 78, Cornell Univ. Agl. Exp. Sta.,
pp. 481-577). It is now out of print.

Approved:
JAMES WILSON,
Secretary.

WASHINGTON, D. C., February 12, 1906.

O

Zier es as wae VARA eas:

RTO TY

SPEARS
_ ‘ ue
SEEN ‘
Ta a SA stun tea! eT aD sth wat

— oo CEU
oe oo aa Be RAGS ue AGORA aR if wae : RNY 1
- . SA oo | ae SAS
se BS oN aA Ae NAyee onl AER UEMURA OREN
Se Le

ae

AS 3x YY

a

. ae ,

8 wy ‘
Mi
yO ane “y

{
?
tds
‘i
.

wae aN
rf . . A ee ae
we Wiis | aS

a

b>: rasy 5
oa oo
Ba wa

EN
SNS
Ne
ite >
NG RAK
| a
w R a x at . a Onan aN
mt Ea SB SRGRNGS ae a
—
; oS

<3 in Ny it «'
YAMS

aks 3 CONE 4
a A
se ony 2) NEN yA SS
: s as Ne
s Ay ARE N QUO ay

Me a .

2

Yes
RY Reo)
PON st

a