CIRCULAR No. 8, SECOND SERIES.

United States Department of Agriculture.

DIVISION OF ENTOMOLOGY.

THE IMPORTED ELM LEAF-BEETLE.

Galerucella luteola Mull. (Galeruca ranthomelena Schrank.)

Fic. 1.—Galerucella luteola: a,eggs; b, larve; c, adult; e, eggs (enlarged) ; f, sculpture
of egg; g, larva (enlarged); h, side view of greatly enlarged segment of
larva; i, dorsal view of same; j, pupa (enlarged); k, adult (enlarged) ; l,
portion of elytron of beetle (greatly enlarged). Irom Riley, in Ann. Rept.
Dept. Agr. for 1883.

GENERAL APPEARANCE AND METHOD OF WORK.

The chief insect enemy of the elm:is the imported elm leaf-beetle, the larvze
and adults of which frequently so disfigure the trees as to make them useless for
shade and hideous rather than ornamental. The beetle—a small, yellowish-
brown insect—appears first and fills the leaves with small irregular holes, while
the following broods of slug-like yellow and black larvie skeletonize the leaves

15162—No, S—06 mM

2

in irregular spots between the veins, working on both surfaces, but chiefly on
the lower side, causing the leaves to assume a dry, brown appearance, to curl,
and ultimately to fall. The second crop of leaves sent out by the trees in the
southern range of the insect meets a liké fate.

DISTRIBUTION.

The elm leaf-beetle is a well-known depredator in the Old World, particularly
in south Germany, Austria, and France. It was imported into this country,
on the authority of Glover, in 1837, and its earliest attacks were particularly
severe about Baltimore and in New Jersey. Its spread in this country has
been comparatively slow, and, while wherever it has appeared it has established
itself very firmly and now frequently occurs in enormous numbers, it is
limited in its range, so far as the records go, to the middle Atlantic seaboard.
including the District of Columbia, Maryland from Washington eastward, Vir-
ginia in the immediate vicinity of Washington, Delaware, southeastern Penn-
sylvania, New Jersey, Long Island, the Hudson River Valley, and southern Con-
necticut. On the authority of Prof. C. H. Fernald it is not known to occur
in Massachusetts, and Prof. Gerald McCarthy reports the same for North Caro-
lina. This range, as pointed out by Mr. Howard, practically conforms to the
northern limit of the upper austral life zone, outside of which the insect has
not established itself as yet, so far as can be learned.

NATURAL HISTORY AND HABITS.

Characteristics of Different Stages.—The insect occurs on the trees in three
different stages, and the fourth stage is passed on or under the surface of the
ground at the base of the tree; i. e., the egg, larva, and beetle on the tree, the
pupa in the ground.

The beetle is a little over a quarter of an inch long, of a general yellowish
or yellowish-brown color, with three somewhat indistinct brownish-black
stripes on the wings. It is shown natural size at c, and enlarged at k, in the
figure. ©

The eggs are placed on the lower sides of the leaves in vertical clusters of
from 5 to 20 or more eggs, Closely arranged in two or three irregular rows.
They are cblong-oval in shape, tapering to a rather obtuse point, orange yellow
in color, and the exterior surface is covered with beautiful hexagonal reticu-
lations. They are shown natural size on the leaf at a, and enlarged at e, with
the reticulated surface still more enlarged at f. 4

The larva is elongate, reaching a length of about half an inch, and when
newly hatched is nearly black. As it increases in size it becomes, with each
shedding of the skin, more distinctly marked with yellow, and when mature
the yellow predominates, occurring as a broad dorsal stripe and two lateral
stripes. The larva is represented natural size on the leaves, and somewhat
enlarged at g, with portions still more enlarged at h and i in the figure.

The pupa is uniformly light orange yellow, oval in shape, strongly convex
dorsally, and a little over a quarter of an inch in length. It is shown in the
illustration at j, enlarged.

The egg state lasts about a week, and the larva normally fifteen to twenty.

days, and the pupa six to ten days.

Number of Broods and Dates of Appearance—In the more southern range of
this insect, including Maryland, Virginia, Delaware, and most of New Jersey,
there are two annual broods, with an occasional small third generation. Far-
ther north, including northern New Jersey, Long Island, New York State, and

(Cir. §]

a

fi
G

be a onal te

ae | 8

Connecticut, there is in general but one well-marked brood, with sometimes a
supplemental or partial second brood.

Throughout the double-brooded area the beetles make their appearance in
spring about the middle of April, beginning to come out before the elms have
put out their leaves and continuing on the trees through May, perishing soon
after egg-laying is finished. The eggs. of the first brood are deposited during
f “May and into June, the larvre of this brood occurring ‘from early in May
: throughout June. Pupation takes place during June and July, and beetles of
the second or summer brood emerge during July and into August. The eggs
for the second brood of larvz are deposited by these beetles from the middle
of July through August, and the larvee of the second brood skeletonize the
= ‘second growth of elm leaves during the latter part of July and August, the
Plater specimens occurring up to October. Pupation occurs chiefly during Au-
gust and September, the beetles appearing from the last of August through
September, and entering winter quarters during September and October.

F In the one-brooded regions the beetles do not appear in spring until the last of.
May, and, in general, the periods are fully a month later for the different stages
than for the southern districts, the beetles of the summer brood transforming
most abundantly about the first of August. After feeding on the leaves a little
~ while, and doing very inconsiderable damage, they go into winter quarters dur-
i ing August and September, remaining dormant eight or nine months.
4 Habits of Larve and Hibernation of Adults.—The lary from each batch of
eggs feed together somewhat gregariously for a time, but ordinarily become sep-
arated and scattered later, especially with a scantiness of food. When full
grown they normally crawl] down the branches to the trunk and then to the
ound, pupating almost immediately on or very near the surface of the soil
ust about the base of the tree. They are apt to seek partial protection about
grass bunches, but frequently accumulate in masses, exposed on the surface in
uch a manner as to make a striking yellow carpet about the tree from a few
‘a inches to a foot or more wide. With very large elms, however, many of the
~ larvee are shaken off by winds or fall directly to the ground, sometimes fairly
covering the surface over a diameter equal to the limb-expanse of the tree.
a / Hibernation is in the adult state both where there is but one brood and where
there are two. For this purpose the beetles frequently enter houses and barns
or outbuildings, sometimes assembling in such numbers that it is possible to col-
ect them by the quart. They also enter cracks in posts, telegraph poles, fences,
ete, or wherever they can secure partial protection from winter storms.
Susceptibility of Different Elins.—BHuropean elms seem to be especial favorites
with this insect, and this would naturally be expected from its European ori-
- gin. Its preference for the European elms is especially noticeable where these
re grown in conjunction with American elms, the former being frequently en-
tirely denuded, while the latter remain practically uninjured. In general, the
coarser-leaved sorts of elms are distasteful to the beetles, and the smooth, thin-
_leaved varieties are especially subject to attack. The American species, Ulmus
americana, is notably exempt, and this, together with the general immunity of
other American species, is a strong argument in favor of restricting planting
to our native sorts. All species of elms, however, are attacked more or less,
and in the absence of sufficient foliage of the favorite varieties, the injury to
_ less palatable sorts becomes almost equally marked.
‘Zg REMEDIES.

In nearly every stage of the life history of this insect it is easily subject to
treatment. The best means against the adults and laryze consist in the use of
arsenical poisons in the form of sprays on the foliage. The adults, fora week

[Cir. 8]

eT

01272 6642

or two after emerging, feed on the newly expanded foliage, and a spraying with
Paris green or other arsenical will destroy the great majority of them. Especial
pains should be taken to accomplish the destruction of the insect in this stage, |
in order to prevent the partial disfigurement which will result if the matter be |
delayed until the larvee begin to appear. If rains interfere with spraying for

the adults, or if it be neglected, the trees should be sprayed with arsenicals
promptly on the first appearance of the larvie, and the application perhaps re-
newed a week or ten days later, especially if rains have intervened.

Paris green is the best arsenical, and may be safely used on elms at the
rate of 1 pound to 100 to 150 gallons of water. If London purple be used, an
sinount of lime equal to the poison in weight should be added to combine with
any free arsenic and prevent scalding of foliage. The liquid should be applied
with a strong force pump with a long hose and a nozzle, such as the Vermorel
or Nixon, which will make a fine mist-like spray. In spraying for the larvee it
is very essential to thoroughly wet the lower side of the leaves, on which they
principally feed. In the case of the adults, this is not so necessary, because
they eat the entire substance of the leaf, and will get the poison from either
side.

On elms 15 or 20 feet in height, the treatment can be made from the ground
or from a wagon. For larger elms, it will be necessary to climb up into
the tree, using a hose 50 to 100 feet long, and directing the spray by this means
into the upper branches. By removing the spray tip from a large size Nixon
nozzle, so as to get a direct discharge, the upper branches of comparatively tall
trees may be reached and sprayed in a more or less satisfactory manner. In
the case of very large elms in city parks or streets, the use of stronger appara-
tus may be advisable, such as a fire engine or steam pump and a larger nozzle,
such as a graduating spray tip, capable of throwing either a direct stream or a
spray. During spraying the poison should be constantly stirred to prevent it
from settling to the bottom of the tank.

The first effort should be to destroy the beetles and larvee at their earliest
appearance, to save the trees for the current year. Sometimes, however, larvze
in the tops of tall trees will escape, and, whenever from inefficient spraying or
neglect they are allowed to reach maturity, a strong effort should be made to
destroy the insect when it reaches the ground to transform, and thus limit or
preyent damage from the second brood or in the following year. The collection
of the larvee for pupation, frequently’ in enormous numbers immediately about
the base of the tree, makes it comparatively easy to destroy them in this
situation. This may be accomplished either by wetting them with boiling
water or with kerosene emulsion, diluted about four times. Frequently they
may be collected by hand or shoveled up, and burned or otherwise destroyed.

Remedial treatment is much simpler in the northern areas of the range of
this insect, where it is single-brooded, and becomes more difficult in the south-
ern districts, where the number of broods is doubled, and the appearance of
the insect becomes somewhat irregular, continuing practically throughout the
sulnimer.

C. L. MARLATT,
First Assistant Entomologist.

Approved.

CuHaAs. W. DABNEY, JY.,
Assistant Secretary.

WASHINGTON, D. C., May 23, 1895.
[Cir. 8]