Pear-tree psylla (Psylla pyricola Forest)

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Pear-tree psylla (Psylla pyricola Forest)
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Marlatt, C. L
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_AR No. 7, SECOND SERIES. 4


United States Department of Agriculture.

DIVISION OF ENTOMOLOGY.
_a


THE PEAR-TREE PSYLLA.


(Psylla pyricola Foerst.)

An overwhIlming invasion af th'e pear-tree Psylla in the summer of 1894 in one of
the largest pear orchards in Matyland, together wiqh similar appearances in Virginia
and New Jersey in 00B same yeSlr gives prominence to an insect which had not pre-
- piously J4een reported south: of New York/,although known to extend westward aa


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7'q.."1q 1.-Pear-tree Psylls: adait female-natural size indicated by side line (original).
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*1wr-As Michigan and to occur generally in the New England States. In view of its
rthern range; its sodden appearance in enormous numbers so far south was
hitiderable surpri4sJ, and caefi minations of the work of the insect
ntBwith remedies were mad
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The pear-tree Psylla (fig. 1) is supposed to have been imported into Connecticut
about 1832 from Europe, where this and one or two other species are well-known
pear enemies. It is one of the true bugs of the order Homoptera, and its family, the
Psyllidie, is intermediate between or connects the scale insects and the plant-lice
on the oue hand with the Cicadas and larger plant bugs on the other. The Psyllid;e
are commonly known as the jumping plant-lice, on account of the considerable
vaulting ability of the adult insects.

NATURE OF THE INJURY.
S
The pear-tree Psylla has hitherto been by no means a common insect, and few pear
growers are familiar with it. The insect, even in the later stages, is small and easily *'
overlooked, but the effects of its presence upon the trees are startling enough, as seeW"
in the falling of the leaves and fruit, the latter before it is half grown, but chiefly
in the enormous secretion of honeydew by the larvae and nymphs. One who has not
witnessed this sight gives credence with difficulty to the reports of the amouJt of
this liquid constantly being secreted. During the height of the invasion in Mary-
land the water-like fluid or honeydew was reported not only to have covered the
leaves and twigs, but to have fairly rained from the leaves, and, running down the
trunks, extended in a discolored circle for from 6 to 8 inches outward around the
base of the trees. During cultivation the horses used became so drenched with the
sticky substance that it became necessary to wash it off with sponges, the curry.
comb being useless. The weakened trees lost much of their fruit, the leaves were
blackened and fell in great numbers, and the bodies of the trees appeared as if they
had been smoked.-
On July 20, when first seen by the writer, the leaves, limbs, and trunks were black-
ened by the growth in the sweetish liquid of the smoky fungus, Futmago salicina;
and in the falling of the foliage and the diseased and smoky-looking fruit a startling
picture of disaster was presented. The leaves were scarcely at all yellowed, but
were covered with dead and dry patches or spots, sometimes investing almost the
entire leaf, giving an appearance which might easily be mistaken for some fungous
attack. This seenime to be due not directly to the extraction of the plant juices by
the insects, but rather to the sun-scalding resulting from the collection of the honey-
dew on the leaves in large drops. The Psylla was distributed over the entire orchard
of upwards of 100 acres, but was much more abundant in the plats of older trees.
The young orchards, perhaps amounting to one-third of the entire tract, were in vigor-
ous condition, and had not been seriously affected. This was noticeably the case
with the Kieffer, Buffon, Le Conte, and Standard Lawrence. The Dwarf Lawrence, on
the contrary, was badly injured, and, with the old Duchess and Bartlett trees, seemed
to have suffered the most.

OTHER OCCURRENCES SOUTH OF NEW YORK.

The presence of this pest, as recorded above, is not the first instance of its occur-
rence in Maryland. A pear orchard about 8 miles south of this one was also very
badly infested in the summer of 1891. The insect appeared during that year on pear
trees next to and in the vicinity of the house, where some nursery stock had been
heeled in the winter previous. Its spread was confined to an area of 3 or 4 acres,
-which, however, was so thickly infested that the leaves and fruit fell, and the trees
were so stunted and injured that they ceased bearing until the season of 1894,
when they bore a fairly good crop. Curiously enough, however, in this orchard the
Psylla disappeared'entirely after the first year and has not again put in an appear-
.ance, nor did it occur in other pear orchards between and in the neighborhood of
the two referred to. Similar outbreaks are reported this year for the first time in

Chestertown (Md.) Transcript, July 19, 1894.








New Jersey by Prof. John B. Smith, with evidences of the sanlt source oft' infesta-
tion, and about the middle of October it was found in Charlottesville, Va:., 1y Mr.
D. W. Coquillett. These records evidence an untfortiuate tendency of thi, insect to
spread southward-a course which, from the history of the peat during the sixty
years of its occurrence in this country, was hardly to be expected.

METHOD OF INTRODUCTION.

The suddenness and severity of the appearance of the Psylla, particularly in the
Maryland instances, makes the question of its introduction one of considerable
Interest. Upon inquiry it was developed that in these cases the pear trees hail been
t' obtained from a New York nursery in 1890, or just at the time when the Psylla
appeared in such extraordinary numbers in New York State; and it is unquestion-
ably from this source that the Psylla was introduced. The young trees secured in
the fall of the year mentioned were undoubtedly infested with hibernating Psyllas,
as it was in the immediate vicinity of the point where these trees were heeled in
that the outbreaks occurred. In one case the insect seemed to have gradually
increased in numbers, reaching a destructive abundance in the summer of 1894.
The entire disappearance of the insect after the first year in the other orchard is
probably to be explained on the ground of some local climatic condition. Such
modifying influences are not unusual in the peach belt of Maryland, as illustrated
by the fact that orchards separated by only a few miles,'and with the same condi-
tions as regards soil and variety of fruit, will
seemingly be so differently affected by very ..
local cold waves or storms that one will be
barren while the other will be full of fruit.

DESCRIPTION AND LIFE HISTORY.

The stages in the development of this
insect are the egg, the larva, the nymph or 7^ Y .
active pnpa, and the adult or perfect winged
insect. The egg (fig. 2, a) is orange-yellow _
in color and so minute as to be almost .....
invisible to the naked eye. Its peculiar
structure is indicated in the drawing-the
short arm serving as its attachment to the F t 6
SFIGo. 2.-Pear-tree Psylla: a, egg; b, larva-
leaf. The newly hatched larva is some- both greatly enlarged (original).
what larger than the egg and yellow in
color, with crimson eyes, and has the characteristics indicated at fig. 2, b. With
each of the earlier molts the form approaches more and more nearly the nymphal
stage, which is represented in its final form at fig. 3. In this stage the prominent
features are the large wing pads. The general color is dark reddish-brown, with the
lighter areas indicated in the illustration-the eyes remaining of a crimson color.
In all the preparatory active stages the insect is broad-oval and very much flattened,
little, if at all, resembling the adult, but rather some scale insect, and is very slug-
gish. The adult (fig. 1) comes from the last nymph, and is a little, clear-winged
insect, closely resembling the Cicada or harvest fly vastly reduced. Like the latter,
its wings close roofwise in repose. Its color is reddish-crimson, with the brown or
S black markings indicated in the illustration. The last or hibernating brood turns
uniformly brownish black, with bronzy eyes and dark wing veins, and was described
S as a distinct species (Psylla 8imnulans), but has been shown by Mr. Slingerland to
be merely a winter., form, which result is confirmed by breeding records at this
Department.


* Bulletin 44, Cornell Agric. Exp. Station, Oct., 1892.






The life history of the insect may be briefly summarized as follows: The adults
hibernate in crevices in the bark of pear trees and emerge with the first warm
spring days, copulate, and begin the deposition of eggs before the leaves have ex-
panded, placing them singly or in rows or bunches in creases of the bark of the
twigs, on old leaf scars about terminal buds, and later, after the leaves begin to unfold,
on the leaves themselves, as already described. The egg laying goes on during April,
probably later in the North than as far south as Maryland. The larvre hatch in from
ten to seventeen days (from ten to twelve days being the ordinary summer period),
station themselves on the leaf petioles and in their axils on the fruit, but chiefly over
the surface of the leaves. The moment they begin feeding the secretion of honey- "
dew commences, and in a very short while the bulk of liquid will be several times
that of the insect, rapidly increasing until it forms a good-sized drop. This, when
there are millions to aid in the work, soon becomes abundant enough to fall as a
shower from the tree whenever it is shaken by the wind. Mr. Slingerland shows
that there are five molts, including the last change from the pupa to the adult insect,
and the life from the laying of the egg to the adult covers a period of about thirty
days, the periods between molts varying from three to seven days.
RECORD OF BROODS FOR MARYLAND.
The adults were very numerous July 20 in Maryland, frequently fifteen or twenty
resting along the midrib of a single leaf. They were depositing their eggs along
the midrib on the upper surface, and also
thickly along the serrated margin, but
on no other part of the leaf. From July
31 to August 3, when again examined,
the eggs were much more numerous and
Qhad been frequently deposited in small
clusters, five to eight together, along the
S'^ midrib and at the margin of the leaves.
'i J :; H Scarcely any of the eggs at this time had
.---m .i i been hatched, at least not more than 2
or 3 per cent, and the adults were still
m S ^almost as numerous as ever and busily
ovipositing. This brood, which was the
J \maximum one of the season, was with
^ little doubt the third one from the hiber-
nating individuals-a month being the
enornial period for a generation. A fourth
F np-gt e brood of adults appeared about the last
FIG. 3.-Pear-tree Peylla: nymph-greatly en-
larged (original). of August, and a fifth about the 1st of
September. In breeding cages over
young potted pear trees no difficulty was experienced in getting the fourth and fifth
broods in large numbers, but in the orchard on the mature foliage-prematurely
mature, from the sapping of the insects-the fourth brood was very scauty in num-
bers, showing not more than one where there were a thousand before, and this in
the face of the fact that more eggs had been deposited than for any previous brood.
The further decrease with the fifth brood was as marked, and the greatest difficulty
was experienced in finding a single adult.
THE FUTURE OUTLOOK.
Judging from the history of the pear-tree Psylla in the North, we may expect that
the injury will be very much less in future, even if there is not an entire cessation
of the trouble and a disappearance of the pest. The fact that this insect was im-

*On potted trees in an unheated greenhouse the adults rested exposed on the
twigs all winter without making any attempt at concealment, and began oviposit-
ing early in March, the first brood maturing early in April. The plants on which
they wintered were, however, in time of leafing, fully four weeks in advance of those
on the grounds.





5

ported into thle United States with pear trees over sixty years ago and w;is lnig
since widely distributed throughout the pear districts of the Northern State.- ,1nil
westward to the Mississippi, and has yet, during all this time, rarely lbeei repulrtedl
as injuriously abundant, argues that the conditions favorable to its incriais' :'ire s.]-
dom met with. Its complete disappearance in one orchard, after a year of exce-s.iv.
abundance, is a case in point; and the excessive multiplication in New York iStat,.
in 1891 was followed the next year, according to Mr. Slingerland, 1by scarcely illyy
injury in comparison. The reasons for the sudden multiplication and quite as s'id-
den disappearance of this pest are difficult to give. A succession of two or three
Swinte-rs favorable to hibernation probably leads to the unusual increase, and the
resulting attack brings the trees into a condition which is probably prejudicial to
the insect. With the later summer broods, as pointed out above, the condition of
the leaves which have been seriously attacked by the earlier broods is sue-h that the
insect becomes markedly less abundant later in the season. The green, succulent
foliage of the young spring growth is especially favorable, and when the leaves


























VFiGA.-Chrysopaoculata Say: a, eggrs;b, full-grown larva; c, foot of same; d, same devouring a Psyl~la;
e, cocoon; f, adult insect; g, head of same; h, adult, natural size--all enlarged except A (original).

become hardened and mature, and especially dry and innutritious, from having been
already sapped of their vitality, they are distasteful and unsuited to the development
of the later broods.














The parasitic and predaceous insects also become very efficacious by midsummer,
and a very interesting experience in the case of the Maryland invasion will be now
noted.
NATURAL ENEMIES.
No enemy for this insect among the parasitic and predaceous species bas, previous
to this year, been recorded. 0u my first visit to the Maryland orchard I was shown
what was taken to be the egg of the Psylla, which proved, however, to be the ego,
-.-
































oacomonlce-inge pCrysopa oculata Say. The mistake was a very nat-
ural one, for the eggs occurred in extraordinary numbers throughout the orchard.
On some trees nearly every leaf would have one or two of the eggs of the Cbrysopa
noted.











fo. 4.-mn aewngdfy Chrysopa oculata Say ,eg ,fl-rw av;c oto same; dmistame deouin a Psryna;-

already saped fof thei vitalcuredity teytraoredistastfu andunbesuiedthouht the deeopmentd

and aover itereestinga experience inl aeon rtoo the case of the Mayanhnvsonwllbsowa





6

attached to it. Later nearly full-grown larvae of the Chrysopa were found on the
pear trees, attacking and devouring the adult Psylla in a very vigorous manner
(see fig. 4, d), and the young larvae were found to feed with great readiness on
both the eggs and the young larval Psyllas. It is a safe estimate to say that one
lace-wing fly larva will destroy several hundred eggs and larvae of the Psylla, in
addition to the adults which it will destroy in its later larval growth. The great
abundance of the Chrysopa eggs on the pear trees makes it not at all improbable that
the lace-winged fly had much to do with the marked decrease in the later broods of
the Psylla.
The predaceous habits of the lace-wing fly larvae are of common record, and their
beneficial character is well known; but in view of the important rdle played by this
insect in the economy of the Psylla, its
S\ life habits may be briefly summarized.
The eggs (fig. 4, a), instead of being de-
posited in rather numerously placed
clusters or groups, as is the case with
some other species, are distributed almost
I invariably singly on the leaves, rarely
S-two together on the same stalk. The
-1.L I young larva (fig. 5) cuts off the upper end
^^.. 4-1^^ of the egg on emerging, and is surpris-
\\i _^. ingly large in comparison with the egg
S from which it emerges. It is light ash-
-~ ~-~gr. gTay in color, the head abnormally large,
-' - ^ s and the body armed with immense curved
f Chairs or spine', which give it rather a
T ferocious appearance and undoubtedly
Z- i[ make it seem to the young Psylla a veri-
/ table dragon. It crawls down the egg
-- Q /^ stalk and begins immediately its active
J- ^searchfor food. On approaching the egg
/ \ _' or young larval Psylla, itf immediately
grasps it between its long, curved, man-
I "L dible-like organs, which amount to two
l ~ sucking tubes, between the tips of which
the egg or the young larva is held and
p n y h e l, rolled one way and the other, as between
FPi. 5.-Chrysopa oculata: newly hatched larva,
with under side of head and claw at side-greatly thumb and finger, the juicy contents be-
enlarged (original), ing in the meantime rapidly extracted.
It is a most interesting sight to watch
this little larva at work and to note with what celerity it grasps the young Psylla,
quickly extracts the juices, and casts aside the dry shell, the whole operation fre-
quently taking less than a minute.
The larva is an extremely hungry one and is always feeding, and its rapidity of
growth is limited only by the abundance of the food supply. It eats anything that
conies in its way, is totally fearless, and is also, unfortunately, cannibalistic, eating
its own kind with as great readiness as it does any other larvae. After about ten
days the larva becomes full grown, and spins up in the curl of a leaf or in any par-
tial protection, constructing a delicate, slightly oval, but nearly spherical silken
cocoon, which is attached to the leaf by silkeu threads (fig. 4, e). This cocoon is very
small, in comparison with both the larva which spins it and the adult which emerges
from it, and is less than one-eighth of an inch in longest diameter. The adult emerges
in from ten to fourteen days, cutting off the upper end of the cocoon in a neat cap.
The fly (fig. 4, f) is pea-green in color, with, in life, bronzy eyes with greenish reflec-
tions. The adult is a very helpless insect, does not feed at all, and remains concealed







in low grass during the day, becoming muora active in the evening ;and depositing
its eggs, so far as observed, only at. this time, though perhaps al.o diirinig the night.
Its sole reason for existing is to deposit eggs, and having accomplished this it dies.
It is a very fragile insect, and can not be handled without being crushed, lint is
withal rather active and difficult to catch. When taken it emits a most disgusting
odor, which seems to be its chief means of protection from enemies. While the
species referred to above was the common one in the orchard in question, theirs
also occurred there. Thie differences bietwevn. these species are so slight, however,
That no one butt a specialist would detect them. and the habits are. practically the
same for all.
S Two or three species of ladybirds were also observed running ahodut ove: the pear
trees, the commonest one being fJdalii bilpunctalta L., a little red species \ ith two
black spots oxt its elytra, (fig. .). This species was seen in the orchard with an
adult Psylla in its mandibles, and in my breeding cage at Washington ono ,ir two
adults cleaned the eggs from tlhe leaves of a young pear tree about ;is fast as upwl ardil
of fifty to seventy-five Psyllas laid them. The larvw of the ladybird (fig. (, (1, %i re
equally active and beneficial, and I had no difficulty in rearing a brood front ti:'c eg"
on the eggs and larv.' of the Psylla.

















a ie
FIG. 6.-Adalia biplunctata: a, larva; b, mouth-parts of same; e, claw of same; d, pupa; e, adult;
f, antenna of same-all enlarged (original).

REMEDIAL. TREATMENTS ADVISED.

: Spraying has practically no value against the adults during their active summer
4* existence, because they are comparatively shy and at the first disturbance fly to
other Vees. The experience gained by Mr. Slingerlaud, and the results of a series
of experiments conducted in Maryland, have shown that the larval periods in the life
S cycle of the Psylla are particularly vulnerable, and of the first brood especially so,
t because occurring when spraying can be most economically and efficientlypracticed.
Spraying to reach the midsummer broods of larv? when the trees are in full fruit is
more or less unpractical, but may be sometimes advisable, particularly with young
orchards. The following treatments are therefore recommended: The first is a spring
application, which should be made immediately after the leaves are well unfolded and
the eggs deposited by the hibernating individuals are hatched. A thorough spraying
at this time with ke-osene emulsion, diluteiLto the normal strength with nine parts
of water, or, if applied earlier, before the eggs are all hatched, with seven parts of
water, will, it seems to me, effect the destruction of practically all the eggs and larvr.
Treatment at this time is especially recommended on account of the fact that it coin-
cides with the periods for the first, or perhaps the second, application for the leaf
blight of the pear, and the kerosene emulsion and the Bordeaux mixture may be corn-




".... UNIVERSITY OF FLORIDA
..11111 tllUlt If i111111111ii1111 I1IHll ~l11111 lii1 B ittfl

I; :: 3 1262 09228 3729
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bined in one application with little additional trouble or emsp,.. Thexeii

already conducted show the complete feasibility of this. i4tfrtkiz 'bieh, briefQy,
consists in using the Bordeaux mixture in lien of water as afdileint Al*L& emulsion,
A second treatment, which promises we'1, is the winter spraying tht"'hbernating
adults. A thorough wettiug of the trunk and limbs at any time darig .'te winter
with kerosene emulsion, diluted from seven to nine times, will reaoh and destroy
many of the insects. It will be more effective if the loose bark be seped f..rom the
trunk and larger limbs before the application is made. .
The source and means of infestation reported for the Maryland orchardfea known
to be paralleled iu the New Jersey cases, and are probably te ofthe W i one. {
They emphasize the advisability, as a precautionary measure, of subjefi :;ur- .. ,
sery sto k, procored either in fall or spring, to an immediate and thorough Sjw '
with Jeroseue emulsion. : ;.
/ C. L. M#01&TT, ...i...
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t. rsssFirst Aasat t u an, ltthh
Wrpproved: : .'1 :9
CHAS. W. DABNEY, Jr., W:r.*.;:r
SA saistaut Secretary. r
WASHINGTON, D. C., May 1, 1895. -0





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? -1


OIlSOULAN No. 7. SECONDo EMniC.

United States D')epairtmnw t (if A\.rri tlture,
DIVISION OF ENTOMOLOGY. "---
"i ,

THE PEAR-TREE PSYIA .' .
.. ( I'-'1"i iffl pyi enI'l l I wr-t.. I L ^ ''r
An overwhelming iinvaqion (f lilt pirar-trr* iM' llI1hO oI th largest pear orchards in "t TirinI, Ii'iglit rr 'ii -iii iyiifrin
;jeI''Imlmals and New JerMty in thle s:iiim' 'ir, i vr lIr-irinvuirre tI an1 inieit
alld not previously been reportedly sou tlh of N-.w Y.irk, :iltliii.gh kin'" toextend

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FI6 1 -It-P r tr e PSylls Adulut eCniale Nii Our i i'Iij nI.'i l 1.n i, 5 li -o i- rizinal
westward as far as Michigan anil to ccuir geein:allv in tin' Niw Englandl States.
In view of its previous northern r:illige. its .*s ilijen .appParance in enormous
numbers so far south was a nimatt'r if ,coi(r:i,]erale surpri-.e, and careful
examinations of the work of the ia rsect 1nril ePperiuiierit. tilli rtmiitilies were
made.
The pear-tree Psylla liug 1i is suippose to have hepen imported into Connec-
ticut about I$182 from Eurnp.,, where this anrid unre or twn oilier species are well-
known pear enemies. It is one of the true hm,p.i of the order Hlomoptera, and
it family, the Psyllidw, is intermediate between or connects Wbe scale insects
d the plant-lice on the one hand with the (.'icadas and larger plant hugs on
e other. The Psyllidr are commonly known as the juniping plant-lice, on
aSwount of the considerable vaulting ability of the adult insects.






UNIVERSITY OF FLORIDA

6 3 1262 09216 5009
out the orchard. On some trees nearly every leaf would have one or two of the
eggs of the Chrysopa attached to it. Later nearly full-grown larvae of Chryopas
were found on the pear trees, attacking and devouring the adult Psylla in a
very vigorous manner (see fig. 4, d), and the young larvae were found to feed
with great readiness on both the eggs and the young larval Psyllas. It is a mafe
estimate to say that one lacewing fly larva will destroy several hundred eggs
and larvae of the Psylla, in addition to the adults which it will destroy in iM
later larval growth. The great abundance of the Chrysopa eggs on the pear
trees makes it not at all improbable that the lacewing fly has much to do with
the marked decrease in the later broods of the Psylla.
The predaceous habits of the lacewing-fly larvzv are of common record, and
their beneficial character is well known; but in view of the important r6le
played by this insect in the economy of the Psylla, its life habits may be briefly
summarized. The eggs (fig. 4, a), instead of being deposited in rather numer-
ously placed clusters or groups; an ie
6 "/ the case with some other species, are
distributed almost invariably singly on
the leaves, rarely two together on the
same stalk. The young larva (fig. b)
cuts off the upper end of the egg on
/ emerging, and is surprisingly large in
comparison with the egg from which it
"-' I issues. It is light ash-gray in color,
\' the head abnormally large, and the
_ih body armed %ith immense curved hair.
or spines, which give it rather a fero-
cious appearance and undoubtedly -
Smake it seem to the young Payll a ver-
S itable dragon. It crawls down the egg
/ ff ^ ^ -stalk and begins immediately its active ..
/search for food. On approaching the
\ egg or young larval Psylla, it immedi-
.^ ~ ately grasps it between its long, curved, i
L^ mruandiblelike organs, which amount to
-- [ ---. two sucking tubes, between the tips of
[| <- -" which the egg or the young larva is held "
n 'and rolled one way and the other, as I
4 Y between thumb and finger, the juicy
contents being in the meantime rapidly ::
Fio. 5.-Chrysopa oculata: Newly-hatched laTra. extracted. Itisamostinterestingsight
with under side of head and claw at to watch this little larva at work and
side. Greatly enlarged.
to note with what celerity it grasps the
young Psylla, quickly extracts the juices, and casts aside the dry shell, the whole
operation frequently taking less than a minute.
The larva is an extremely hungry one and is always feeding, and its rapidity
of growth is limited only by thlie abundance of the food supply. It eats anything
that comes in its way, is totally fearless, and is also, unfortunately, cannibalistic,
eating its own kind with as great readiness as it does any other larva. After
about ten days the larva becomes full grown, and spins up in the curl of a leaf
or in any partial protection, constructing a delicate, slightly oval, but nearly
spherical silken cocoon, which is attached to the leaf by silken threads (fig. 4, e).
This cocoon is very small, in comparison with both the larva which spins it and
the adult which emerges from ii, and is less than one-eighth of an inch in long-
mst diameter. The adult emerges in from ten to fourteen days, cutting off the





4

warm spring days, copulate, and begin the deposition of eggs before the leaves
have expanded, placing them singly or in rows or bunches in creases of the
bark of the twigs, on old leaf scars about terminal buds, and later, after the
leaves begin to unfold, on the leaves themselves, as already described. The
egg-laying goes on during April, probably later in the North than as far south
as Maryland. The larvte hatch in from ten to seventeen days (from ten to
twelve days being the ordinary summer period), station themselves on the leaf
petioles and in their axils on the fruit, but chiefly over the surface of the leaves.
The moment they begin feeding the secretion of honeydew commences, and in
a very short while the bulk of the liquid will be several times that of the insect,
rapidly increasing until it forms a good-sized drop. This, when there are mil-
lions to aid in the work, soon becomes abundant enough to fall as a shower
from the tree whenever it is shaken by the wind. Mr. Slingerland shows that
there are five molts, including the last change from the pupa to the adult insect,
and the life from the laying of the egg to the adult covers a period of about
thirty days, the periods between molts varying from three to seven days.
RECORD OF BROODS FOR MARYLAND.
The adults were very numerous July 20 in Maryland, frequently fifteen or
twenty resting along the midrib of a single leaf. They were depositing their
eggs along the midrib on the upper sur-
Sface, and also thickly along the serrated
margin, but on no other part of the
S. leaf. From July 31 to August 3, when
"" again examined, the eggs were much
more numerous and had been fre-
j -^ rquently deposited in small clusters, five
to eight together, along the midrib and
at the margin of the leaves. Scarcely
S any of the eggs at this time had been
S hatched, at least not more than 2 to 3
Sj per cent, and the adults were still al-
/ W most as numerous as ever and busily
y ovipositing. This brood, which was
|the iaxiuiium one of the season, was
^ V with little doubt the third one from the
i hibernating individuals-a month be-
Pi. 3.-Pear-treePJylla Nymphli-greatly ing the normal period for a generation.
enlarged. (Original.) A fourth brood of adults appeared
about the last of August, and a fifth
about Septemblir 1. In breeding cages over young potted pear trees no diffi-
culty was experienced in getting the fourth and fifth broods in large num-
bers, but in the orchard on the mature foliage-prematurely mature, from the
sapping of the insects-the fourth brood was very scanty in number, show-
ing not more than one where there were a thousand before, and this in the
face of the fact that more eggs had been deposited than fur any previous brood.
The further decrease with the fifth hrood was as marked, and the greatest diffi-
culty was experienced in liinling a singlee adult.
THE -'UT'ltIE OUTLOOK.
Judging from the history of thle pear-tree Psylla in the North, we may expect
that the injury will be very much less in the future, even if there is not an entire
cessation uf tht trouble and a disappearance of the pest. The fact that this
insect was imported into ilih United States with pear trees over sixty years ago
and was long since widely distributed throughout the pear districts of the




-OW


2

NATURE OF THE INJURY.

The pear-tree Psylla has hitherto been by no means a common insect, and
few pear growers are familiar with it. The insect, even in the later stages, ia
small and easily overlooked, but the effects of its presence upon the trees are
startling enough, as seen in the falling of the leaves and fruit, the latter before
it is half grown, but chiefly in the enormous secretion of honeydew by the larvae
and nymphs. One who has not witnessed this sight gives credence with diffi-
culty to the reports of the amount of this liquid constantly being secreted. Dur-
ing the height of the invasion in Maryland the waterlike fluid or honeydew was
reported not only to have covered the leaves and twigs, but to have fairly rained
from the leaves, and, running down the trunks, extended in a discolored circle
for from 6 to 8 inches outward around the base of the trees. During cultivation
the horses used became so drenched with the sticky substance that it became
necessary to wash it off with sponges, the currycomb being useless. The weak-
ened trees lost much of their fruit, the leaves were blackened and fell in great
numbers, and the bodies of the trees appeared as if they had been smoked.'
On July 20, when first seen by the writer, the leaves, limbs, and trunks were
blackened by the growth in the sweetish liquid of the smoky fungus, Fumago
salicina; and in the falling of the foliage and the diseased and smoky-looking
fruit a startling picture of disaster was presented. The leaves were scarcely at
all yellowed, but were covered with dead and dry patches or spots, sometimes
investing almost the entire leaf, giving an appearance which might easily be
mistaken for some fungous attack. This seems to be due not directly to the
extraction of the plant juices by the insects, but rather to the sun-scalding
resulting from the collection of the honeydew on the leaves in large drops. The
Psylla was distributed over the entire orchard of upwards of 100 acres, but was
njach more abundant in the plates of older trees. The young orchards, perhaps
amounting to one-third of the entire tract, were in vigorous condition and had
not been seriously affected. This was noticeably the case with the Kieffer,
Buffon, Le Conte, and Standard Lawrence. The Dwarf Lawrence, on the con-
: ,* trary, was badly injured, and, with the Old Duchess and Bartlett trees, seemed
o to have suffered the most.

S'OTHER OCCURRENCES SOUTH OF NEW YORK.

The presence of this pest, as recorded above, is not the first instance of its
L occurrence in Maryland. A pear orchard about 8 miles south of this one was
also very badly infested in thIe summer of 1891. The insect appeared during that
year on pear trees next to and in the vicinity of the house, where some nursery
stock had been heeled-in the winter previous. Its spread was confined to an
area of 3 or 4 acres, which, however, was so thickly infested that the leaves and
fruit fell, and the trees were so stunted and injured that they ceased bearing
until the season of 1S94, %hen they bore a fairly good crop. Curiously enough,
hn% ever, in this orchard the Psylla disappeared entirely after the first year and
has not again pit in an appearance, nor did it occur in other pear orchards
between and in the neighborhood of the two referred to. Similar outbreaks are
reported this year for thle first time in New Jersey by Prof. John B. Smith, with
evidences of the same source of infestation, and about tlhe middle of October it
was found in Charlottesville, Va., by Mr. D. W. Coquillett. These records evi-
dence an unfortunate tendency of thie insect to spread southward-a course
which, from the history of thIe pest during thie sixty years of its occurrence in
this country, "as hardly to be expected.

Slhe-tertown llrd.) Transcript. July 19. 1904.








Mil' ioll OF IN i'lH l l i'll% .
The suddenness and sLvtrriiLyv ,f tI he appiinrnl- ,.f thle I'm, lii. particularly in
the Mlaryland instauices, niilkest tli t' ,,istliin rif it- iltiro]ll,.iirtl ,in ip of corn.iidir-
able interest. IUpon inquiry it was devhlmped ih it iin tIe,-, r.isi.-4 tit' )pear trees
had been obtained from a New York nurmtrsry in I.N'I,. -r jli' 10 Ilihr titie R hlnn
the i'sylla appeare-d in suclh extraorilinary" nubiiiler- il N.' Y.,-ik Statr. andl it
is unquestionably friiiin this s'iirrce tlhat thle l'sylla w.%s iritr,,,liirel. Thil yuun
trees secured in tlie rail 1if liti 'vnir rientiiirlted terv il..liiIte.Ill inft.-ted uitllh
hibernating Psyllasi, as it Aatn in thel iimnidiatu vit'iinty il thle p,.ril % Ili ri, tlhi'et
trees were heeled iil that ilh' oih breaks ccii erriI. In ,iii cu'i, tih ien-vec '(t'i,,iitl
to have gradually iiecrl'i-,etl iii iliriiiers., riachiing a dei.,trnuci'm-i :liiilanercr in
the slninireorof Is'll. Tht Pntire iiialile'aranrct if tliht inli-cl afttr tice rlirst year
in the other orchard is prihahhly to hie expilaiinedil onli the gro-iiindl if sleiii. local
climatic condition. Such iiiil' if'ing inhtliince, al not iinisimal in tliil pacurli
belt of Maryland, as illustriated ijy the fact that irclird- sel'larliteil bIy liily n I f'ew
miles, and with li tlie sane conidiiions as regards :ii an!d arielt iof fruit, %ill
seemingly be so differently affected by
very local cold waves or stornos that one
will be barren while thie other will lIe full
of fruit. .
DiEiCRIPTION AND .I 111FEI i i S 'O I \.
The stages in thit dev('lopine'int of this I
insect are the egg, tIhe larva, tille nymiilih
or active pupa, andti the adiIll or perfrt'l,
winged insect. The egg I fig. 2, 111 i'4
orange-yellow in color and so mninule an.
to be almost invisible to thlie naked irve.
Its peculiar structure is inidicaLtd in ll1 ,
drawing-the short arni .se-rving as it'
attachment to the Ieaf. TIe neuly vF.- P-e'ar ir. P'-Illa a. -:Fk'. t. iart a.
Ihrlieru a' ett, iml.irLr'l I'I l ri>'tictl i
hatched larva is soniehat larger than
the egg and yellow in color. ilti crii srii *vi'-, and hins ihicharacteriitics indicated
at fig. 2, b. With each if thlie earlier itiolt t l-r fbrin anpproache. nioire nnd iiore
nearly the vniymphil stiagtp, Mlicli is representeid il iit tinal formni at fig. 3. In
this stage the promiiinenit faturt,- are the large niiii-pad. Thln general ceilor is
dark reddish-brown, % ith thie I lighter :ar iii lcl.Ial I ii I he iilhltraLion-le t.i ee
remaining a crimson color. In all the, preparitory active stages tlie ins.'ct is
broad-oval and very niitch ilatte'neI. little, if at all. reseiielulng, the adtlIlt, lltL
rather somine scale insrt,, anti i.. ery hiiggi-h. The adlt i fig. I i comics froni
the last nymph, and is ii litlle, cleai- i llged insect, closely rr-.uihelling the Cicada
or harvest fly vastly reduced. Lik, thIP latter, its ings clo.p roofwise In repose.
Its color is reddish-criiesni, tilth tle li rown or black miiarking-4 indicated in the
illustration. The last i'r li trn, iti ng I ir', iod turn- unifornily v Lriwnigh black, with
bronzy eyea and dark iig-%eint, antid was described as a distinct speci- i /'is /lla
similans). but has been sheot n by IMr. Slingerland I to be ieerelv a %%inter firm,
which result is confirui,., v l ereeling records at this Diepartiient.
The life history ,f the insect rmiav be briefly siimeiinari.zed as i,,'lo"-: The
' adults hibernate in crevice-; in the bark of pear trees- and erierge with the first
I Bul. m14. C.'ornell Air. Ell. Steiiii i i- '2
l On potteI tree. in an ulL':ille igrt 'nh.eill" Ih a'i.ilb ri" ti, j'.'', e'l inn ill, ItWi- oill uinl, r
wtlhout niali tfi l an)- attei l''t E cen e.'ninlnt atilI t' ein iio.ip.iiriiii- early in Mar h Lii,' ilir-i
brood inAtUrinir early in April. The i0ilau1 on1 wtiivh Ihr v 'uintetre,.lt 'rr liit" 'r ie Ilni,. .f
leafiing. fully teur week% in aitl mnre of thole on the grountl









Northern StIa.i anI I %% %it rd to the %I I -.i' I] 3. and has yet, -.I i, I aill I i
tilIPe, r[ar hlv t. eni rtp-l rt.,l I as, 1 iijir',ii, Il i pli it. :irgiiJ. Ilil l til l ',i l 11.l.In .I4
I favorahle tu its incr ase are *Il..i, met wIith. Its v'npl I. ti lijqi ;rairan'.t in
one orchard, Itlter a Yv:ir uf excessive 11.111i1.i- is a case in pihil, ; Mid thel
excesimk* inliitilili'ii;dln in Nt.\ York .iI., in Il[. wa ( ,I lI next .%-ir,
S according to Mr. Shiiierlauid. I.% scarcely ;iiii ilijiir[ in r.,ii,;LnFii There-ons
: for th.ie eilden iiimiltipli'ati-,ni mai l q, it as sudden ilv:it ]..ir.i.', of this ji'-t are
'' ditfficuiilt to give. .A succ\ sion ,,f two oir tree winters fiIr:iIt' to hibernation
S probably lead. tvi the unusual increase, and the t -i, til; attack tiring. ili.. trees
into a cofnditiIn Hhich is prihalit pirluliiiii.I to the insect. With hil later
S suuni ier hrDools. as ipoinited out :ilii,'. tite t,,ili' ii ri f the leaves which have
S been seriutly aiacke(d Iv thi. rO rl.r lii, iii.. Is such IliIA th insect becomes
r markedly Itei aliihniant later in the season. 1 I,. nr..rii succulent i')liait. i of the











'i'I

















Pil I.- CArf o,'I -,u ,t- .n(.i(if N % 't b. !,il! .:r-,,r n larea; l foot of saune ; d, a eu dI-vourlng a
I 'N-lli. co'.-o.i /. Iilult insect: u. head of same; hA, adult, natural sie All enlarged except
h I I i)r tlial )
young spring grontli is p-pir'i.ility ia':,r:ili].. and when the leaves become hard-
ened and matitre, and '-prci,. dry :ind iuatiiriii,,ij-, from Ilav ing been alrea.ly
sapped of" their vuialutv, thtcy are ji'tm-il'ul :niii iintiiiied to the development of
the later brn.ids.
The parasitic anl prvdacr',m, insects also become very ,'ilicaIii, by mid-i-
sumnimer, and a verv intere-tinn rxperi.rirt- in the case of the Maryland invasion
will be now noted.
NATURAL ENEMIES.
\ No enemy for lii< insect ninlilg thfie parasitic anid pruilact'iI-; cp.cif- has,
previous to this year, been recirdol. On rniv firct visit to the Mar lanil orchard
I was shown what was taken to bethe fegg if the I'%lla, which provedI, however,
to be the egg of a common lacewinug iH', ('hiriiiiii oculata Say. Tri' mistake
was a very natural one, for the eggs occurred in extraodinary numbers iri-,iiil. ,-


41-S