aberdeen e
decade toute

A

noesn

os
Eee
SSMS
cast nee
‘a

iyit

coy
oe. <

, és Perna

are ay

H
ve

Sinton

<

a

A
AA
ans

een

ot

mare kona.
SAE
towns
Spe how’
Se Te

Carsexensetes

Na ac St eae a sve
ee if

vy
an Ag <i

oy weal

; aa)
reer GS ie ee
an 9; ca cn

He ‘ ei

Pavit -
4 or

<. hy
; ey ..

WV eeis ids mn et
re io :

ty 0D gine
: ie " ae
oi ni

aa
act

Tees

a a] ey Th

Historic, archived document

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

Pye2

wo. /05.

CIRCULAR No. 105. Issued October 5, 1908.

United States Department of Agriculture,

BUREAU OF ENTOMOLOGY,

1 (O). HOWARD, Entomologist and Chief of Bureau.

THE ROSE SLUGS.

By F. H. CHITTENDEN,
In Charge of Truck Crop and Special Insect Investigations.

Roses grown in gardens in the United States are attacked by three
species of sawfiies which live, in their larval stages, on the foliage,
skeletonizing the leaves or cutting out holes of variable size and
greatly disfiguring the plants. The larve, popularly known as “ rose
slugs,” “ slugworms,” and “ roseworms,” have been classified as the
American rose slug, the bristly roseworm, and the coiled or curled
roseworm, respectively. For the sake of uniformity they may all be
called rose slugs. The first of these, as its common name indicates,
is native to America; the other two are evidently accidental intro-
ductions from Europe, as they are now common to both hemispheres.
As with most other sawflies,? they are found more abundantly in the
North, but are quite troublesome as far southward as Maryland and
Kansas. They practically confine their depredations to the flower
garden, and roses are the only plants that are seriously damaged by
them. Injury is due entirely to the larve, and the three species, each
representing a distinct genus, differ considerably in appearance in all
stages, as also in their life history and manner of work.

THE AMERICAN ROSE SLUG.
(Endelomyia rose Harr.) ?

The American rose slug was first identified as a pest about the year
1831, when it did damage in gardens at Cambridge, Mass. At that
time the species was somewhat restricted to that locality, but later,
according to Harris, who observed and studied its habits,’ it grad-
ually spread in that vicinity and by 1840 it had become so great a
nuisance that a premium of $100 was offered for the most successful
method of destroying it.

@ Hymenopterous insects of the family Tenthredinide.

®’ Synonyms: Monostegia rose and Selandria rose.

¢ Report Ins. of Mass. Inj. to Veget., 1841, pp. 380-3882; Flint ed., pp. 525-528.
54115—Cir. 105—08

2
DESCRIPTIVE.

The sawfly which produces the American rose slug is a four-winged
bee-like insect (fig. 1, @) of a deep shining black color, with trans-
lucent smoky wings having dark-brown veins and a brown spot near
the middle of the edge of the forewings. The wing expanse of the
female is about two-fifths of an inch and the length of the body is
fully one-fifth of an inch. The male is a little smaller.

The larva or slug (0, figs. 1,2) when full grown is about one-third
of an inch long and sluglike, with the thoracic joints enlarged. The

‘ She
Ses,
BS

6

Fig. 1.—American rose slug (Hndelomyia rose): a, Adult sawfiy; 6, mature larva; c¢,
work of larve on rose leaf; d, section of rose leaf, showing location of egg near upper
margin; e, egg in situ on bit of rose leaf. a, b, e, Much enlarged; c, less enlarged; d,
about natural size. (Original.)

body is soft and delicate, but not gelatinous: and slimy, as is the case
with some sawfly larve-—for example, the pear slug. The color is
green above and yellowish on the lower surface. The head (fig. 2, ¢)
is small, oval, and yellowish, and has a black spot on each side,
imclosing the eye.

DISTRIBUTION.

The assertion has been made by Riley ¢ that this sawfly undoubtedly
criginated in New England, where it fed upon wild rose. With the
lapse of years, if we assume this statement to be correct, it has been
disseminated by commerce into neighboring States and through the

@ American Entomologist, Vol. III, 1880, p. 115.
[Cir. 105]

3

importation of rose bushes trom eastern nurseries to western gardens.
Owing to the sluggish habits of the female, its distribution by flight
has undoubtedly been very slow. Its occurrence in New York, New
Jersey, Ohio, Illinois, Michigan, and Missouri has been known for a
number of years, and it undoubtedly occupies intervening States.

In 1904 we received reports of injuries by it in Pennsylvania, New
York, Maryland, and Kansas; in that year it also appeared at Char-
lottesville, Va., and the following May reached the District of Colum-
bia, where it has been quite abundant since. In 1908 it was reported
injurious at Cincinnati, Ohio.

Mes

Fic. 2.—American rose slug (Endelomyia ros@): a, Lary, natural size, upper larva at
work on upper surface of leaf, lower larva at rest on under surface; b, larva, dorsal
view, enlarged; c, head of larva, more enlarged. (Original.)

LIFE HISTORY.

The parent sawflies issue from the earth at varying times from
about the 1st of April, or earlier in the District of Columbia, to the
third week in May, or, according to Harris, until the middle of June
in Massachusetts, beginning at about the time when the roses first
unfold their leaves and continuing until they are in full leaf. During
this period pairing takes place and eggs are deposited. The females
are particularly sluggish in the cool of morning and are not often seen
in flight, resting during the greater part of the day on the leaves.
When disturbed they draw up their legs and fall to the ground. The
males, however, are quite lively, flying from one rose bush to another
and hovering around their less active partners.

[Cir. 105]

=

The female in depositing her eggs turns a little to one side,
unsheaths her delicate saw-like ovipositor, and thrusts it between
the two cuticles of.a leaf, depositing a single egg in each incision. An
egg is shown about natural size at d, figure 1, and much enlarged at e.
The egg is of circular outline, much flattened, and measures about
one-twentieth of an inch in diameter. Hatching begins in from
ten days to two weeks after the eggs are deposited.

The larve or slugs are to be found at work as early as the Ist of
May in the District of Columbia, but their appearance in numbers is
seldom noticed until the second or third week of that month. Obser-
vations conducted at Washington, D. C., show that the periods men-
tioned are subject to considerable variation. In 1905 the first
sawflies of the new generation appeared June 2. Owing to the
irregularity of appearance of the parent “ flies,” larvee of the first
generation may be found at work for a period of five or six weeks.
Feeding takes place chiefly at night, and always on the upper surface
of the leaves, the lower surface, ribs, and midribs remaining as a
skeleton (fig. 1, ¢). The leaves are practically always skeletonized,
not eaten into as in the case of the other two rose slugs, except when
the larve are nearly grown. During the daytime the larva usually
rests concealed on the under surface of a leaf (fig. 2, a).

Sometimes the larvee are so abundant that not a leaf on a bush is
spared, and the foliage looks as though it had been scorched by fire,
and eventually drops off. The larvee are stated to be between two
and three weeks in attaining their growth. They cast their skins
several times, leaving them fastened to the leaves. After the last
molting they lose their greenish hue and become opaque yellowish.
They then descend into the earth to a depth of an inch or more, and
each constructs for final transformation a somewhat fragile oval cell
or cocoon coated with particles of earth. Here the insect remains as
larva until the following spring, when it transforms to pupa shortly
before issuance in May.

The species is single-brooded, in which respect it resembles many
other species of sawflies.¢

REMEDIES.

This rose slug and the others which will be discussed are quite
easily controlled by several different methods.

Sprinkling with water.—A strong stream of water directed upon
the plants from different sides by an ordinary garden hose or large

2@JTt is evident from Harris’s account (1. ¢c.) that in ascribing two generations
to this rose slug he must also have had the bristly rose slug under observation.
Miss M. E. Murtfeldt writes on this head that she has disproved Harris’s state-
ment “ by repeated rearing of the insect under close observation.” (41st Annual
Rept. State Hort. Soc. Missouri, 1898, p, 288.)
[Cir. 105]

5)

syringe, if applied every day or two, will soon rid rosebushes of the
pest. This is at the same time an excellent remedy for rose aphides
or plant-lice. The insects are dislodged, fall to the ground, and are
unable to return to reinfest the bushes. This remedy was tested
practically by Dr. L. O. Howard many years ago.

Paris green.—Where it is possible to apply them without danger
of poisoning human beings or disfiguring the plants for ornament,
different poisonous preparations are useful. Of these, Paris green,
either dry or in solution, arsenate of lead, and white hellebore are
good remedies. Paris green is best used as a spray in the proportion
of an ounce to a gallon of water. Applied dry, it is mixed with 20
parts of flour or similar diluent and puffed on the plants by means of
a powder bellows or insufflator. For use in large gardens, however, the
poison is employed at the rate of 1 pound to from 75 to 125 gallons
of water, lime being added in about the same proportion as Paris
green to prevent scorching. For properly mixing and applying this
insecticide a sprayer of good quality should be used. Sprinkling
with a watering pot or with a whisk broom will not answer the pur-
pose and is, moreover, dangerous to tender foliage. The Paris green
is first mixed with a small quantity of water into a fine paste before
the bulk of water is added and should be churned in the sprayer or
force pump until thoroughly blended. The resulting mixture, being
a mechanical one, is not constant and the arsenical sinks to the bot-
tom. The solution should therefore be constantly stirred while
being applied in order that an even application may be made. In
applying an arsenical spray an effort should be made to reach all of
the leaves, which may be accomplished by spraying from two sides.
Two or three applications will suffice for the spring generation of
rose slugs. Scheele’s green and some other arsenicals can be used
instead of Paris*green.

Arsenate of lead.—A._ still more valuable insecticide for such insects
as rose slugs and other leaf feeders is arsenate of lead, but its use is
open to the objection that it discolors the leafage, leaving a white
deposit, which is not, however, permanent. It 1s apphed in practi-
cally the same manner as Paris green and is a less poisonous arsenical,
and, being sold in paste form, is used at a considerably greater
strength—about 1 pound combined with 15 to 25 gallons of water or
Bordeaux mixture. Being adhesive, it adheres more firmly to the
leafage and is much less likely to produce scorching.?

Hellebore.—Hellebore is used at the rate of 1 ounce to from 2 to 3
gallons of water, and kills by contact as well as by its poisonous effects

2 Additional information in regard to the preparaticn and use of arsenate of
lead and other insecticides is given in Farmers’ Bulletin 127, which may be
had gratis on application to the U. S. Department of Agriculture.

Cire 051

6

when eaten by the insect. It is less poisonous to man than an arsen-
ical, but not so effective to leaf-feeding larve. It may also be applied
dry mixed with about double its weight, or more, of powdered plaster
or cheap flour.

When not in use the receptacles containing poisons should be
plainly labeled “* Poison! ” and placed on a high shelf or in a locker
out of the reach of children. Properly applied, there is no danger,
in using an arsenical on ornamental plants, of poisoning human
beings, or domestic animals’other than rabbits or similar pets.

Soaps and other washes.—Oily soaps, such as fish-oil or whale-oil
soap, and other soaps, and tobacco water will kill these insects, but
their use is open to the objection that if applied just before or at
blossoming they are apt to injure the petals of delicate flowers, and
whale-oil and tobacco also leave an unpleasant odor. <A neutral
soap, such as castile or that used by physicians and surgeons, leaves
no odor.

Dry powders.—Fine, sifted road dust, where this can be readily
procured, is also of value thrown upon the plants, preferably by
means of a powder bellows, as it closes the breathing pores of the
larvee and thus kills them. Finely powdered lime, and buhach (Per-
sian insect powder, or pyrethrum) are also effective.

Hand picking.—tlf rose slugs are picked off by hand upon their
earliest appearance this will greatly reduce their numbers for the
following year. In the adult or “ fly” stage these insects may be
easily captured by hand on cool mornings. Hand picking may be
tedious, but it is effective.

Fall Paionalane —If other means that have bean specified have not
been utilized for the suppression of the slugs, many individuals may
be destroyed by frequent cultivation of the soil Between the rose
plants during the late summer and autumn. This has the effect of
breaking up their pupal cells and otherwise disturbing the insects so
as to interfere with proper hibernation.

THE BRISTLY ROSE SLUG.
(Cladius pectinicornis Fourcr.)

The bristly rose slug, called also the spiny rose slug, is the principal
enemy of the rose in and near the District of Columbia, not excepting
the rose-chafer. It is believed to have been brought in from Europe
some time prior to 1833, since it was mentioned by Harris in his
catalogue of Massachusetts insects of that date. In the early
seventies it was reported from Connecticut and in after years it made
its way westward and southward, doing more or less injury where-
ever established. Since 1880 it has done much mischief in Wash-

[Cir. 105]

ee rman

i

ington, D. C. In 1886 it was reported from Lafayette, Ind. In
1889 it was observed to be injurious at St. Charles, Mo. Soon after-
wards it was recognized as a pest at St. Louis, where it attracted
considerable attention.

DESCRIPTION AND DISTRIBUTION.

The adult of this species (fig. 3, a) differs considerably from that
of the American rose slug, as will be readily seen by a comparison of
the illustrations of the two forms. It is a larger insect and a mem-
ber of a different genus. The wing expanse is about one-half of an
ineh for the female; a little shorter for the male. The ground color
is black. The antenne are rather stout and acutely pointed, and in

Fic. 3.—Bristly rose slug (Cladius pectinicornis) : a, Adult female; b, antenna of. male;
c, larva; d, head of same; e, female pupa; f, cocoon. All enlarged. (Reengraved after
Riley, except d, original.

the male the proximal joints, or those nearest the head, are pectinate

or comb-toothed (fig. 3, b), which has given rise to the specific name

pectinicornis.

The egg (fig. 4, a) is white, flattened, rounded, stoutest at the
anterior end, and more pointed at the opposite end. It measures about
0.8 mm. in length.

The larva or slug, shown in figure 3, c, and figure 4, c, d, varies
from yellowish to glaucous green, and the whole surface is quite
bristly, especially at the sides, a character from which this larva de-
rives its common name and which will distinguish it from the other
two that feed upon the rose. The length when full grown is a little

[Cir. 105]

8

more than three-fifths of an inch and the diameter is between one-
tenth and two-tenths of an inch.

The pupa (fig. 3, e) is grayish green, the thorax and end of the
body are slightly yellowish, and the antenne, wing-sheaths, and legs
are white with a slight greenish tinge.’

The distribution includes the States of Massachusetts, Connecticut,
New York, New Jersey, Pennsylvania, Maryland, the District of
Columbia, Indiana, Illinois, and Missouri.

It is generally distributed on the continent of Europe and occurs
also in England and Scotland.

aaaAS

iN

N

3
q
H
Ge
ha 3
a;
“Be
f ie
re as
4 3
Bi iz
|

PR Os

RON

Fig. 4.—Bristly rose slug (Cladius pectinicornis): a, Egg; 6, portion of leaf showing
eggs in situ and work of young larve: c, d, lateral and dorsal aspects of middle seg-
ment of newly hatched larva; e, larval claw; f, rose leaf showing nature of defoliation.
All except f enlarged. (Reengraved after Riley.)

LIFE HISTORY.

The bristly rose slug differs considerably from the preceding in its
life economy. Its appearance at Washington, D. C., and at St. Louis,
Mo., has been observed from the latter days of April to the third
week of May, beginning about the time that the first rose leaves are
put forth. Its eggs are inserted in the upper surface of the petiole
of the leaf and are deposited in rows of three or more together.

The slug in its earliest stage skeletonizes the leaves, leaving whitish
blotches and small holes (fig. 4, 7), but with increased growth it eats
large, irregular holes in the leaf (fig. 4, 0), devouring the entire sub-

*More detailed descriptions of the stages are furnished in C. V. Riley’s
article, Insect Life, Vol. V, pp. 6-11, which includes accounts of the other two
species here treated.

[Cir. 105]

9

stance, and frequently leaving nothing but the stronger ribs. While
feeding, the slug rests in concealment on the lower surface of a leaf,
and does not feed on the upper surface, as does the American rose
slug. Upon attaining full growth it does not, like the latter, aban-
don the plant upon which it has fed until the final generation. Indi-
cations are that there may be three and, in some seasons in its
southernmost range, perhaps four generations produced each year,
larve occurring as early as the 1st of May and as late as the 1st
of November. In northern Europe two generations are recognized.?
The larvee of the earlier generations spin their cocoons (fig. 3, /),
which are composed partly of silk and partly of a glutinous sub-
stance, upon the lower surface of the leaves, or on twigs or near-by
objects, usually surrounding them with an irregular fringe. The last
or autumn generation forms its cocoons among fallen leaves and other
rubbish about the base of the rose bushes.

The egg period in late April and early in May has been observed
in the District of Columbia to last for from seven to ten days, and
the young larvee begin feeding in the first and second weeks of May.
Larve grow rapidly, and cocoons have been found by the middle of
May. The pupal period observed was fifteen days, so that the second
brood of flies may appear before the end of May. This second gen-
eration begins work about the second week in June, but during July
there is a comparative cessation, presumably between the second and
third broods of worms, when fresh growth is ttle affected.

Mr. G. Pauls, St. Louis Altenheim, St. Louis; Mo., wrote in regard
to observations conducted by him on this species at St. Louis in 1904.
The sawfly continued depositing eggs up to September 17. October
14 he placed larvee in a jar; three transformed to pupx October 17,
19, and 24 and issued March 30 to April 10 of the following year.
One larva pupated October 16 and issued March 22, having passed
about five months in the pupal stage. This shows considerable varia-
tion in the time of issuing indoors, and would probably be duplicated
to a certain extent in the open. April 29 he observed the sawfly
depositing eggs on the leaves.

NATURAL ENEMIES. ;

No natural enemies of this rose slug appear to have been recog-
nized in America, but in Europe it is preyed upon by two parasites,
Acrotomus lucidulus Grav. and Mesochorus cimbicis Ratz.

4Various European authors have written on this species. One of the most
accessible general articles is that by M. S. C. Snellen van Vollenhoven, trans-
lated from the Dutch by J. W. May and published in The Entomologist, Vol.
VIII, 1875, pp. 26-29.

[Cir. 105]

10

REMEDIES.

The same remedies advised against the American rose slug are em-
ployed against the present species, with the exception of fall cultiva-
tion, which is practically useless when applied. to it, owing to the
fact that the cocoons are formed upon the plants on the surface of
the ground and not buried in the earth as with the preceding species.
Since there are more than one generation of this slug, sprinkling
with water and spraying with poisons must be repeated several times
in order to produce the desired results; in short, as often as the
insects reappear upon the plants, from April to October, according to
locality.

THE COILED ROSE SLUG.
(Emphytus cinctus 12)

The third of the rose slugs under consideration, the coiled rose
slug, is a comparatively recent importation. As with the two pre-
ceding species, it first attracted attention near Boston, Mass., but
not until the year 1887.” It is probable, however, as in the case of
most European insects introduced into this country, that its 1mporta-
tion was accomplished at a considerably earlier date. Reasoning
from analogy, this insect might have been brought from the mother
country on potted roses ten or twenty years earlier than the date
specified, as that length of time is sometimes necessary for a foreign
insect to become permanently established so as to attract attention
by its injuries.

DESCRIPTION AND DISTRIBUTION.

From the two preceding species this insect may be readily sepa-
rated on account of its larger size in the adult stage (fig. 5, a). It has
nearly transparent wings, and a wide band which crosses its shining
black abdomen near the middle. The body is comparatively slender,
and the head longer than in the other two species. The wing expanse
is about five-eighths of an inch and the length of the body about three-
eighths of an inch.

The larva when mature is about three-fourths of an inch long and
differs notably from the other two species here considered in being
perfectly smooth. It is cylindrical and tapers very slightly toward
the posterior extremity. The color is metallic green above, orna-
mented with small white dots, and the lower surface, including the
legs, is grayish white. The head (fig. 5, ¢) 1s yellowish orange, with
a dark brownish-black stripe down the middle. The eyes are black.

4AHmphytus cinctipes Nort. is recognized as a synonym.

oJ. G. Jack, Garden and Forest, Mar. 26, 1890, pp. 151-152.
(Cin 105i

MAGEE Ngee

12

The first thoracic segment is blue and the last two are gray.*. The
larva habitually rests in the coiled or curled position shown in
figure 5, b, one that is never assumed by either of the other rose slugs,
and it is from this habit that it derives its English name.

In addition to Boston, it has been authentically reported from
Jamaica Plain, Roxbury, and New Bedford, Mass.; portions of
Maine; Allegheny, Pa.; New York, and Canada. In the Eastern
Hemisphere this species ranges over the major portion of Europe,
extending into Siberia.

NATURAL HISTORY.
The coiled rose slug is credited with being double-brooded, and as

it extends its range southward it will probably produce a third gen-
eration, since we know of the appearance of the “ worm” from May

Fig. 5.—Coiled rose slug (Hmphytus cinctus): a, Adult female; 6b, full-grown larva; ¢,
head of same; d, work on plant; e, eé, young larve at work. d, e, Natural size; a, b,
enlarged ; c, more enlarged. (Reengraved after Riley.)

to October. Eggs are deposited singly on the underside of the

leaves to the observed number of from three to seven. This slug

differs from the others in devouring the entire substance of a leaf,
feeding along the edges with its body coiled beneath it, and when at
rest remaining curled in a ball on the lower surface (see fig. 5, @).

Upon reaching maturity the slug deserts the leaves and bores into

the pith of the stems of dead rose bushes or other available plants,

and here the pupal state is passed, the fall generation hibernating to
emerge the following May. At Boston, Mass, the adults have also
been observed in July, this indicating the first new generation.

@A more technical description by Dr. H. G. Dyar is given in the Canadian
Entomologist, Vol. XXVI, p. 186.
[Cir. 105]

12
NATURAL ENEMIES.

A parasitic enemy of this species was reared by the writer from
larve received from Allegheny, Pa., in 1904. It issued October 20,
and proved to be a tachina fly, Zachina rustica Fall.

In Europe an ichneumon fly, Uryptus emphytorum Boie., is para-
sitic upon this sawfly.

REMEDIES.

The remedies are the same as for the American rose slug, subject,
however, to the same changes as for the bristly rose slug.
Approved:
JAMES WILSON,
Secretary of Agriculture.
Wasuineton, D. C., August 4; 1908.
[Cir. 105]

oO

<5
wee
a
SON

Coty! " . ‘ een : “ x
wake S . f re " s le

ae - Nw -: . x f ¥ . nts Sew : 7% Saw . s + ~
eS Sena ;
hase oe aber

we
Sa

x.

=

BARS
Sart Cheats aN

o
-~,

ae
apy
bas

Ree oie

pat mas Sona at $ 3 hn ie ; 485 a" A :
Dae eae : fs : : = me

Siac ¢ Arne Mey is s : : MOET NAAT oa Eten eat as Vos: ‘ : : Tear eA ;

SEAN, See Gh Neate ®t

ae