ee rr a ey ~ be * ~ - Y ~ ie ot > Y iy < y yet , v ov, Acad ptt She | ) 4 * Nem
PAT poe : * : “! - ine 5 ey, - 3 " Pests 7 Sin ate Race oS ae ont
= ers ; My Se eet
Hats sry” ? b
yee

Che id : ; . i
Delete 2 Fossey : Sopereceh . er Un So
Scanian 3 ae

“, ae

"econ

se
zs
eres
<

ates

2

owns
SSN

ton tee

a

i
iy
2h

*
»
ry

Ree
Re

cra . wr

<i
i
i

a

#

<<
on
a

Re
siejemenas
Rene

“#55

=

»

oo

i
ie
Pe

en
boitn 8 2%.
Coencth
oo
ae) . “~ _" ES
Ex) y . g
aakes : : Mos. A ad Nyprm 3 % mat

—
oe ae a

ray

ire Se
Ray

aetna

ona

rt ee ay
i a : :

ee ae if val iJ

me: ; mir : ee

ey! ae
Pet) at :
ri. : rT a we
ae ine Oy

(nr

Dae ane
a ie

: if
-
TAM, hk ts
we)

arts

iy Wy ite
Fy she
yi

i
e

Historic, archived document

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

Issued March 23, 1910.

sO biakot MENT OF AGRICULTURE;
BUREAU OF ENTOMOLOGY—CIRCULAR No. 119.

L. O. HOWARD, Entomologist and Chief of Bureau.

THE CLOVER ROOT-BORER.

BSG

F. M. WEBSTER,
In Charge of Cereal and Forage Insect Investigations.

24617—Cir. 119—10

WASHINGTON : GOVERNMENT PRINTING OFFICE : 1910

=

BUREAU OF ENTOMOLOGY.

L. O. Howarp, Entomologist and Chief of Bureau.
C. L. Maruart, Assistant Entomologist and Acting Chief in Absence of Chief.
R. 8. Currron, Executive Assistant.
Cuas. J. Gruuiss, Chief Clerk.

F. H. CHItTENDEN, tn charge of truck crop and stored product insect investigations.
A. D. Horxrns, in charge of forest insect investigations.

W. D. Hunter, in charge of southern field crop insect investigations.

. M. WEBSTER, in charge of cereal and forage insect investigations.

. L. QUAINTANCE, in charge of deciduous fruit insect investigations.

. F. Puriites, in charge of bee culture.

. M. Rocers, in charge of preventing spread of mcths, field work.

Roiia P. Currie, in charge of editorial work.

Mase CoLcorp, librarian.

Do & hy

CEREAL AND ForRAGE INSECT INVESTIGATIONS.
F. M. WEBSTER, in charge.

Geo. I. Reeves, W. J. Pumurrs, C. N. Arnstie, E. O. G. Ketty, J. A.
Hystop, V. L. WinpERMuTH, R. A. Vickery, T. H. Parxs, HERBERT
OsBoRN, agents and experts.

[Cire 119i

(11)

CIRCULAR No. 119. (REVISION OF CIRCULAR No. 67.) Issued March 23, 1910.
United States Department of Agriculture,

BUREAU OF ENTOMOLOGY,

L. O. HOWARD, Entomologist and Chief of Bureau.

THE CLOVER ROOT-BORER.

(Hylastinus obscurus Marsham. )

By F. M. WEBSTER,
In Charge of Cereal and Forage Insect Investigations.

INTRODUCTION.

The clover root-borer (Hylastinus obscurus Marsham) is not a
native of America, but has been introduced from Europe and has
established itself in the fields of red clover in some sections of the
eastern United States, as well as throughout the States of Oregon
and Washington, wherever clover is grown. It frequently commits
serious depredations by burrowing in the roots, thereby destroy-
ing the plants. It has long been known in Europe as a clover pest,
Eichoff? giving its distribution as Germany, Aus-
tria, France, England, and the Canary istends:
Other European entomologists have also written
of its occurrence, and, according to Bach,
infested large fields of clover near Odenbach,
Germany, in 1803, an occurrence evidently coin-
cident with its description by Marsham in 1802.

While it did not come to notice in America as
a pest until about 1878, when it was found in
destructive abundance in central New York, it
probably occurred in this country long prior to i
that date. Dr. A. D. Hopkins, who is making a Fic. 1—The clover root-
special study of this group of beetles, viz, the [Jiwaset Morena
Scolytidee, has shown the writer aspecimen, from at right. (Author’s illus-
the collection of the late Doctor Fitch, with a New "0°"?

York label attached to the pin, referring to a note which he has been
unable to find. In all probability, however, this specimen antedates
the discovery of the insect by Riley in 1878. Besides, owing to the
obscure habits of the pest, it is more than likely that it was injurious
to clover even prior to this date without, however, having been
detected by farmers. Even at present, both in the Middle West
and on the Pacific coast, where it is most destructive, it has
attracted little attention, the effects of its ravages being usually

a Die Europiischen Borkenkiafer, p. 97, 1881.
(Cir. 119] (1)

2

attributed to adverse meteorological conditions. The pest seems
to have spread much more rapidly westward than southward, as it
probably occurs in the East nearly to the Mississippi River; but it
has attracted no attention along the Atlantic coast south of Penn-
sylvania. In that State, however, the writer found it abundant around
Chambersburg, but not disastrously so, in October, 1905. It has not
been reported at all from the vicinity of Washington, D.C. It is cer-
tainly not seriously injurious in the New Eng-
land States at the present time, the late Dr.
James Fletcher reported a similar state of
affairs in Ontario, Canada, and we do not
recelve any reports of its occurrence between
the Mississippi River and the Rocky Mountains.
In Ohio, West Virginia, Indiana, and south-
ern Michigan it 1s becoming more and more

destructive.
Fic. 2.—The clover root-borer:
Larva or grub. Much en- DESCRIPTION OF THE INSECT.
larged. (Author’s illustra-
Hon.) The fully developed insect is a small, dark-

brown, hard-bodied beetle, shown enlarged in figure 1.
The larva, or grub, shown enlarged in figure 2, is about an eighth
of an inch long, dingy white, with honey-yellow head and brown jaws.
The pupa (fig. 3) iseven smaller than the larva, also dingy white,
with two minute spinous projections on the top of the head and two
somewhat larger ones at the anal extremity. The eggs are elliptical,
white, and minute, yet large enough to be seen with the unaided eye.

LIFE HISTORY.

In the East there is certainly but one generation annually, though .
this appears to be long drawn out, and scattering indi-
vidual larve and pupe may be found throughout every
month of the year. The finding of eggs as late as Sep-
tember 18 has been reported from Michigan. As arule,
however, the insects pass the winter in the adult stage
(fig. 1) within the roots where they developed. During
May they abandon the old roots and seek out fresh
plants or fields in which to lay their eggs. The eggs
are mostly deposited between the middle of May and
June 20. The female gouges out a shallow cavity,

D : Fic. 3.—The clover
more often in the crown of the plant, sometimes at root - borer:
the sides of the root even 2 or 3 inches below the up. Muchen-

: 5 c larged. (At-
crown, and in this places, singly, but not farseparated, thors _ ittustra-
about half a dozen pale whitish, elliptical, very minute =")
eggs. These hatch in about a week, and the larve (fig. 2) for a time ~

[Cir. 119]

5)

feed in the excavation made by the mother, but soon burrow down-
ward into the root, and before the Ist of August the majority of
them have become fully grown and passed into the pupal stage
(fig. 3). By October nearly all have become fully developed beetles,
but they make no attempt to leave the plant until the following
spring. Bach states that the adults fly at
Omeegnen in March and April, while Eichhoff
has observed them near Milhausen, swarming
during the warm afternoons about the middle
of June; but these observations were all made
in different parts of Europe. In our own
country, in Ohio, the adults are abroad and
have been swept from clover fields early in
May; but no swarming of the beetles has been
observed, though it is clear that they may
migrate about that time of the year.

FOOD PLANTS.

In Europe, besides red clover and alfalfa,
_the species is known to attack Scotch broom,
Cytisus (Spartium) scoparius, and goat root or
yellow-flowered rest-harrow (Ononis natriz).
In America it has so far been especially de-
structive to red clover (Trifolium pratense),
yet with the recently increasing interest’ in
the growing of alfalfa (Medicago sativa) in
the Northern States it may be expected to
become destructive to that crop also. Besides,
it is known to attack mammoth clover (77-
folium medium) and alsike (7. hybridum).
The fact that it also injures the garden pea
will be very suggestive to growers of peas for
canneries, and indicates the undesirability of F'¢. 4.—Clover root, showing
° : work of clover root-borer.
sowing peas early in the season on ground _ giightly enlarged. (Author's
that has recently been in’ these clovers or __ illustration.)
lying adjacent to the infested clover fields. Late-sown peas, how-
ever, would probably not become sufficiently large to invite attack
until after the beetles had appeared and gone.

METHOD OF ATTACKING RED CLOVER.

The insect’s method of attack is well illustrated by figure 4, show-
ing a clover root split in two, exposing the excavations. In cases
of extreme abundance, however, almost the entire main root,
except the bark, is eaten, the substance being displaced by

[Cir. 119]

&

excreta, and the dead top either becomes detached of itself or is
easily broken off if one attempts to pull up the plant. It will be
observed at once that until the roots have attained sufficient
dimensions it will be impossible for the insect to attack them. Over
the territory where red clover is grown in this country the seed
is sown either during late winter or spring; and during the first year
the roots of the plants have not yet attained sufficient size to
accommodate the insects at the time the latter are, with the excep-
tion, perhaps, of a few belated individuals, abroad and depositing
their eggs; and thus the plants are almost, if not, indeed, entirely,
exempt from attack the first year. Hence it is not until the sum-
mer of the second year that the plants are destroyed. This has led
European entomologists to believe that, like many others of the Scoly-
tidee, the insect does not attack the plant until the latter has become
weakened by age or is diseased. But in this country, at least, this
can not be true, for the reasons just given. It is not improbable,
however, that, as between two plants with roots of the requisite size,
an unhealthy one would be preferred by the beetles rather than one
in a thoroughly vigorous condition. But as yet there have been
no observations tending to verify this hypothesis. A diseased clover
root, or one that has begun to decline from effects of age, is first
affected at the heart; and, as will be observed from figure 4, this is the
part first attacked by the root-borer.

EFFECT UPON THE PLANT.

While an infested clover plant sooner or later succumbs to an attack
by this insect, life may be lengthened or shortened by meteorological
conditions. Thus, if the spring or early summer is very dry, the
plants begin to die in patches late in June, as soon as the hay crop is
removed; but if there is much rain during this period, the weakened
plants may continue to live until winter, dying out before spring. In
either case the farmer is likely to be misled and to attribute the loss
to the weather. The summer of 1905 was not a dry one. Copious
rains fell with sufficient frequency to enable ali but the most seriously
affected plants to survive. A prominent seedsman of Indiana, who
was much among clover fields, thus described the situation in October:

In driving around this year and examining clover fields, we have found that several
fields which apparently should have produced an immense amount of seed, or at least,
say, 30r4 bushels to the acre, * * * did not shakeout anything. We pulled up
some plants and discovered that the plant broke off at the crown; or if any of the root
did come with it, it was small and decayed. On close investigation we discovered a
little white worm which seemed to be in abundance and working amongst the roots.
We noticed this in a number of fields and have been wondering what it was. We have
also had samples of clover plants from other sections of Indiana showing these condi-
tions, and almost invariably the yield of such fields was less than a bushel per acre,
and in many instances hulling was abandoned and the huller taken out of the field.

[ Cir. 119]

4)

NATURAL ENEMIES.

While Doctor Riley found the larva of one of the common soldier
beetles, probably Telephorus bilineatus Say, attacking the larve of the
borer, and although it probably has other enemies, both among
insects and birds, these have so far proven of little economic impor-

tance.
PREVENTIVE MEASURES.

The only preventive measure yet tried that gives any promise of
success is summer fallowing as soon as the hay crop is removed.

At this time the young are in an immature state and, if deprived
of food, must perish. ‘They can not migrate from one clover root to
another, and, if the meadow is now broken up, throwing the roots
up to the hot sun and winds, these wither and dry, thus no longer
supplying the necessary sustenance, at this time so imperative to the
life of the larve, and they perish. Thus an invasion of a new field
from an old one may be prevented. But if the fallowing be delayed,
even for a few weeks, the larve will then have for the most part passed
into the pupal stage, during which no food is required, and plowing can
have little or no effect upon them. This measure, together with the
practice of allowing clover fields to stand only two years, would soon
reduce the pest to subjugation in any community. No trouble from
its work seems to occur in pastures. Once brought under control,
it would seem that a system of rotation that involves mowing for
hay and seed the first year, and pasturing and then breaking up the
ground the following year, if generally followed in a community,
would suffice to keep the pest in subjection. Extermination is not
possible.

Approved:
JAMES WILSON,
Secretary of Agriculture.
Wasuineton, D. C., January 12, 1910.
[Cir. 119]

O

As

) oa 7 Rea
PA : : : . a
ye ee . Y 2 : . : ns es way
ASE . : : :

es

. NS
“SN

“ ¥.
noes

oe)

Sa eT
SS
naa

fs ee

ie

S persia Eh 3S

rem 7 - .
Se * Re Bae Nraehee ee

ao
Reese

~ s

va
Syn

ens Maoh : " } : Os:
ann ~ t, nes ‘ 4 - Se
Nine Ses Seet ; es it

Sas

ae!
emer
RA
eat,

oA
PLN Niven tahe