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DOMINION OF CANADA
DEPARTMENT OF AGRICULTURE
ENTOMOLOGICAL BRANCH
C. GORDON HEWITT, DOMINION ENTOMOLOGIST
THE PEAF THRIPS
{Taeniothrips inconsequens Uzel)
AND ITS CONTROL IN BRITISH COLUMBIA
BY
A. E. CAMERON, M.A., D.Sc.
AND
R. C. TREHERNE. B.S.A.
Field. Officers
BULLETIN No. IS
Published by direction of
Hon. T. A. CRERAR, Minister of Agri. re, Ottawa
OTTAWA
J. !>■ LABROQUERIE TACH£
PRINTER TO THE KING'S MOST EXCELLENT MAJESTY
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DOMINION OF CANADA
DEPARTMENT OF AGRICULTURE
ENTOMOLOGICAL BRANCH
C. GORDON HEWITT, DOMINION ENTOMOLOQI8T
THE PEAR THRIPS
(Taeniothrips inconsequens Uzel)
AND ITS CONTROL IN BRITISH COLUMBIA
BY
A. E. CAMERON, M.A., D.Sc.
AND
R. C. TREHERNE, B.S.A.
Field Officers
BULLETIN No. 15
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Publiihed by direction of the
Hon. T. A. CRERAR, Minister of Agriculture. Ottawa
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OTTAWA
J. Di LABRuQUERIE TACH£
PRINTER TO THE KINGS MOST EXCELLENT MAJESTY
1913
[ISSUED MAY 8. 19ll>
36197—1
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Ottawa, Jaiiuarj- 22, 1918.
The Honourable
The Minister of Agriculture,
Ottawa.
Sir,— I have the honour to submit hr- jiritb for your approval Entomological
Bulletin No. 15, entitled " The Pear 1 ips (Taeniothrips incoruequeru Uiel)
and its Control in British Columbia " uich has been written by t>. a. E.
Cameron and Mr. R. C. Treheme, Field Officers.
In many commercial and other orchards on Vancouver bhint. ' .e has
been for a number of years a very serious reduction in the crops of apples, plums,
prunes, and cht ries owing to a cause which could not be determined. In certain
cases, well-cuUivited orchards were almost wholly unproductive. In 1915 the
pear thrips was discovered in the region in question, and we soon determined
that it was the factor responsible for the losses which the fruit growers were
experiencing each year. This was the first anu only record of the occurrence
of this insect in Canada. In view of the losses for which it had already been
responsible in the infested region in British Columbia, the serious damage it
was causing in the states of California and New York, and the importance of
checking its spread in Canada, we immediately undertook an investigation. The
life-history, habits, and control of the insect under British Columbia conditions
were studied. After determining the most satisfactory spray and suitable
methods of application, demonst'-ntion work in c mmercial orchards was carried
on. The practical results of this i.. , Tstigation h been of signal and immediate
benefit to the fruit growers in the infected ret ; in one of the orchards the
crop was increased tenfold lait season bj the adoption of control measures.
Notwithstanding' the occurrence o*' i his pest in the state of New York, it
has not yet been found in nv aart of C. hnJa other than Vancouver island and
the adjacent islands in Brit : Columbia. It is very important, however, that
a very careful watch should be kept for its first appearance in any other of the
orchard sections of British Columbia or in eastern Canada.
I have the honour to be, sir,
Your obedien^ servant,
C. GORDON HEWITT,
Dominion Entomologist,
I:
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36197—2
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We shall be pleased to hear from any one concerning damage or trouble of
any kin 1 due to insect pests. No postage is required on such letters of inquiry
when addressed : —
Dominion Entomologist,
Department of Agriculture,
Ottawa, Ont.
Such inquiries should be accompanied in all cases where it is possible by speci-
mens of the insects. The insects should be sent packed with their food plant in
a strong wooden or tin box to prevent loss in transit. Packages up to 12 ounces in
weight may be mailed free, and every package should bear or contain the sender's
name and address, and be accompanied by a le' ter.
tuble of
inquiry
f speci-
)Iant in
inces in
lender's
CONTENTS.
PAOI
Summary 7
Introduction 9
Historical —
Known distribution 10
History of species in British f^olumbia H
Distribution in British Columbia H
Synonomy of the species and its systematic position
The Order Thysanoptera 12
Common names .!..........!.... 12
Life-history —
The Eir— DescriptioB 13
Period of em-laying 13
Duration ofen-staae 13
Emcapacity of adult Ij
The l«rva--^«criptioB .......'. 17
First-state larva 17
Second-staae larva 17
Duration of larval stage Ig
Number of moults 18
Depth of larvc in the ground 19
The prepupa— Description 20
Duration of prepupal stage 20
The pupa— Description 21
Duration of pupal stage 21
The Adult — Description 22
Duration of adult stage 23
Longevity of adults in captivity 23
Migration of adults from soil to tree 24
Determination of the date of adult emergence 25
Emergence ofadults in relation to temperafire 29
Habits-
Food plants— Native and cultivated 31
Susceptibility of fruit trees to attack 33
Damage to pears 33
Damage to apples 35
Damage to prunes 37
Damage to cherries 37
Reproduction —
Ovipositioa 3g
Parthenogenesis 41
Control of the pear thrips—
Spray mixtures 42
Hiscible oil No. 2 42
Whale-oil soap 43
Nicotine sulphate 44
Lime sulphur 44
Arsenate of lead 44
Results of spraying 45
Method of recording results 45
Value of two and four sprayings 45
Value of early and late sprayings 4S
Budding chuactertiaics of trees 47
When and how to apply the sprays 48
Climatic factors 48
Cultivation 48
Schedule of applications 48
Preparation of spraying mixtures 48
Types of machines and noiiles tO
Acknowledgments SO
References 80
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36197—21
ILLUSTRATIONS.
Fio. 1.-
2.-
9.-'
10.-
n.-
12.-
13.-
14-
15.-
16.-
17.-
18.-
19.-
20.-
21.-
22.-
•The pear thrips, Ttteniolkripa incoiuequens; eggs. i93 13
Mica-chimney cage in position on a pear twig as used in oviposition experiments with pear
thripa. 15
■The pear thrips, Taeniotkripi inconaequeiu; larva recently emerged from the egg, ventral
aspect. X 200 17
The pear thrips, Taeniothript ineoiuequem; full-grown larva, dorsal aspect, x 90 18
■The pear thrips, Taeniolhript inconsequem; pupa, first stage, dorsal aspect, x 100 20
The pear thrips, Taeniotkripi inconse^uem; pupa, second stage, dorsal aspect, x 100 21
The pear thrips, Taemolhript inconaequeiu; adult, wings outspread, x 95 22
Duchess apple buds. May 3, 1917. Adult pear thript may be seen on the bud on the right-
hand side 25
Trap emergence-box used in the orchard at Royal Oak, Vancouver island, 1917, for deter-
mining the first appearance of thrips in the spring and their numbers in the soil. 26
-Combined trap-cone and cylinder of tin used for holding the glass vials, and fitted into
the holes of the soil emergence-boxes, in the orchard at Royal Oak, Vancouver
island, x 2 27
-Inverted, muslin, bag-net trap in position; a convenient method of deteimining the dates
of emergence of adult thrips from the soil in the spring 28
-Straight-line curve showing emergence of adult pear thrips in trap cages under trees in
orchard, Royal Oak, Vancouver island, March 28-April 25. Dotted curve is a
graphical representation of average daily mean soil temperature during the same
period 29
-Showing a destroyed blossom-bud and an injured blossom-cluster of the broad-leaved
maple, Acer macropkpUum, May 8, 1917. Injury caused by the feeding activities
of the adult pear thnps 31
-Egg-scars on the leaf-petioles of the broad-leaved maple, Acer macropkyllum, sifter eggs
of pear thrips have hatched. May 31, 1917 32
■A, Blossom buds of Bartlett pear; B, Olivet cherry, showing destruction by the feeding
activities of adult thrips in early spring 34
-Egg scars on young develoning apple-stems. May 20, 1917. Larva) of pear thrips have
emerged, rupturing the tissue and thus accentuating the scars. The pubescence
of the stems has been partially removed to show the scars more clearly enlarged. 36
■Olivet cherry infested by larva of pear thrips, May 31, 1917 37
Immature Olivet cherries showing chaiscteristio " russetting " caused by the feeding
activities of the larve of pear thrips. May 31, 1917 38
■The pear thrips, Taeniotkripe iseoiueQiMiM,- terminal abdominal segments of adult, to
show the ovipositor, x ISO 39
■Transverse section in outline of fruit-stem of Italian prune, to showetgf«hambers («.c.)in
the outer layer of cells (cortex) . Drawn from actual specimen, e, epiderm ; e. cortex ;
ee, chlorophyll layer of cortex; e.k., hair; e.c, egg-chambers; f.v.b., fibro-vascular
bundles; m., pith, x 115 39
Transverse section of cherry stem to show the egg-chambers (ex.) in the outer layer of
cells (cortex), e. Head of larva (I) recently emerged in egg-chamber also shown.
Drawn from actual specimen. x6S 40
■The pear thrips, Tamiotkripe incontequens. Adult in the act of ovipositing in fruit-stem
of apple; ovipositor extended and represented asembedded i- theplant tissue, x 126. 40
THE PEAR THRIPS {Taeniothrips incomequens, Uzel) AND
ITS CONTROL IN BRITISH COLUMBIA.
By a. E. Cameron, M.A., D.Sc.
AND
R. C. Treherne, B.S.A.
Field Officers.
SUMMARY.
For many years orchardists of Vancouver island have annually experienced
a decided reduction in their crops, owing to a " blighting " of the Sm budV
fTi ?oX .T^^t •"/'^t.'S'^!; -^^ *^^* ^^^ '°«« ^^ attributedTo spring
iLkL' Tvr * iwif ^^.^'^''^•^ certain orchard sections appear to be peculiarly
mi-* ^°* ^^" ^^^ A&mf,fi,e, however, could be ascribed to this c^se. In
T^t-tt^^ discovered that severa orchards were overrun by the pearthrips,
Taenwthnpa incomequens, and to this insect alone the greater propor^on of the
damage is now known to be due. The minute, glossy-brown insect meMure^
PnH"of°M*T*''!,\^^ ''I •'?''^™ ^"«th, and is^sullly fim observedTth^
end of March and the beginning of April actively moving around in large
fiHlv nr«*',^l P ""P?"'"** ^^^^' ^?"^*th the enveloping scales of which thfy
iSe^^c^ltse^rrmlSh^s'^^ ""'^"*"" ^" '""^ '''''' *^^^ ^^ ^een dormant
Life-history.
The emergence from the soil continues up to the middle of April, the maxi-
mum number appearing from April 1 to 14. This practically coincides ^th
the time of the bursting of the buds of the various fruit tree^s on vSo^er
™l\iT * /•' ^''''% ^?^^'/ °'?^°?'* '^^^'^ ^^^ ad»'t« enter and feed on the
young delicate tissue of the developing parts within. Almost as soon as the
leaves and blossom pedicels appear, the adults begin to lay their eggs. The
SHff*^f tJ^ generally laid about the middle of April, and the last Kbout the
middle of May. The period of maximum oviposition usually extends from April
fL? ^^ *u ^^^^ f""" '^'? '" '^«,^'* numbers on the petioles and midribs of
Sf lt^r'V°" the outer surface of the calyces of the young fruit, as well as on
nrnhlK! ikT^K ^^^V^'i'}'^^ about fivc to Seventeen days to hatch, and it is
probable that the great majority hatch in about fourteen days under the con-
ditions prevailing on Vancouver island.
„«„if™°j*' P'""u *°^ cherries, which are more tardy in their development thi.n
apples and pears by almost a week are attacked later by migrating individual:'.
Sn T^'^^r'?"^ •' ^^^^^^'^ °y ^^^ ^""^^ °^ t^'esc fi'^t i« proportionally greate^
than what obtains on apples and pears. It is well to bear in mind that the most
before^Somln ^^^^ '^ associated with the buds just after bursting and
K„ t ^^A '^'^f "J*"*^ *''*'.'■. ''"* appearance at the beginning of May, and are to
TnlS "♦K °" J*"' ^'^^' ';"*u" *Jl^ "'^'^'c of June. In great abundance they occur
inside the calyx-cup of the blossoms, lacerating its tender tissue and feeding on
the nectar. They are also to be found on the back of the leaves, shaded from
the sun, busily sucking the leaf-juices. When at rest, they are generally to be
found ranged along each side of the midrib and chief veins. When the larva
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attack the young fruit in numbers, they cause a " russetting " of the skin which is
known as " thrips scab." They appear in maximum numbers from May 20
to June 5. The individuals remain on the trees for about three weeks before
they are fully fed.
When mature, the larvte fall to the ground which they enter by any con-
venient crevice or crack. They may penetrate quite deeply, depending on the
character of the soil. In the clayey soils of the Saanich peninsula no larva was
found below a depth of 15 inches. The greatest numbers occur nearer the
surface, at about 6 to 10 inches. Very few are found to occur in the surface
mulch of cultivated orchards. In uncultivated orchards, quite a number of
larvae penetrate no more deeply than the stratum of interlacing grass- and weed-
roots. They remain in the soil for three to four months before transforming to
prepupae in their tiny earthen cells.
The prepupal condition lasts for only one week to ten days at the end of
September and the beginning of October. The prepupae tran-form to true
pupae, the last of which are found in November. The great majority of the
pupae remain as such for six weeks to two months. During November the
pupae become adults, and in this condition they remain in the soil for about five
months. At the end of March and the beginning of April of the following year,
they omerge from their winter quarters and make their way to the trees.
There is but one brood of the species each year.
Remedial Measures.
As a result of a thorough study of the various remedial measures for
the pear thrips undertaken diu-ing the springs of 1916 and 1917, it may be
confidently stated that this insect can be readily controlled. Spraying offers
the only satisfactory means of combating its ravages, and the energies of the
orchardists must be concentrated to cope with the adults and larvae on the
trees in the spring. It is primarily essential that the orchardist should learn
(1) to recognize the thrips, (2) to watch very carefully for its first appearance on
the buds. By following this advice the first step in control will have been accom-
plished. It has been conclusively shown that spraying against the adult thrips
is more important than against the larvae. Hence, if circumstances demand the
application of only two sprays, it is better that they both be applied before blossom-
ing rather than one spray before and the other after. Three sprayings may be
arranged for in instances of severe infestation, in which case two applications arc
made before blossoming and one after. In the case o." h moderate degree of
infestation, two applications of spray are alone necessary. Both of these should
l>e made at a time when the thrips are observed to be " running " on the outside
of the buds. Usually the first application is made on a bright warm day in
spring after the buds have just begun to burst. The second may be made in the
week preceding the period of maximum bloom. The third spray is directed
against the larvae in the calyx-cups and on the leaves just after the fall of the petals.
It has been demonstrated that for the first application the best results
attend the use of miscible oil No. 2 in combination with nicotine sulphate.
Whale-oil soap, also combined with nicotine sulphate, is the most suitable and
economical for the second antl third sprays. Lime-sulphur has been shown to
possess very poor penetrative and spreading qualities, hence its potency as a
controlling agent for thrips is merely confined to those insects with which it
comes into direct contact. Therefore it should only 'le used to replace the second
and third api)lications of whale-oil soap in cases of light infestation and wherc^
it has been found necessary to undertake control measures for " scab." On no
account must it be inferred that the first application of miscible oil can bi
dispensed with. Miscible oil, by rem'on of its greater powers of penetratinu
the young buds, has been found to be the best remedial ajp^ent in the first spraying.
The use of whale-oil soap at this time, whilst often satisfactory, is less effectivi
than the oil.
9
INTRODUCTION.
The pear thrips, Taeniothripa inconse^juens Uzel, w-iS discovered on Van-
couver island for the first time in the spring of 1915 in an orchard at Royal Oak,
four niilM norta of Victoria. Previous to this, the insect had not been observed
m British Columbia. It is probable, however, that it ht^ been present in the
province for at least ten years, if not more. In the opinion of orominent orchard-
ists, the characteristic injury r-aused by the pear thiips to the buds of the various
deciduous fruit trees, has existed more or less in their orchards during that
period; but the damage was not associated wi''i the presence of this apparently
insignificant, but very important, pest until 191.5.
The fact that, in the absenc of treatment, the average annual loss due to
the thrips in the infested areas of California, is computed at over $2,000 000'
—a figure which would naturally increase with time— has been more than sufficient
incentive to an early combating of its activities in the province of British
Columbia.
Three separate r 'd badly infested districts were selected in order to prosecute
investigations, all situated on the Saanith peninsula of Vancouver island. At
I * o^' '" addition to the general or ird spraying, a small section containing
^jout 200 trees was set apart for the p pose of experiment and demonstration.
Here, too, a laboratory was established by the Entomological Branch of the
Dominion Department of Agriculture, to facilitate the undertaking of an
extensive and intensive study of the life-historv and habits oi the pear thrips.
At the two remaining centres, Keating and Gordon Head, a campaign of experi-
mental spraying was undertaken as at Royal Oak with a view to discovering
the most sat'sfactory and economical means of controlling the pest under local
conditions.
It is not possible to give figures with any degree of accuracy illustrating
the loss ol cro) that occurred annually on Vancouver island. It can be quite
confidently - .ted, however, that in the last seven vears the prune and pear
crops have been a negligible quantity in certain sections. The trees have produced
a wealth of blossom and the prospects appeared bright for an excellent return of
fruit, which did not, however, materialize. In some cases the fruit buds were
destroyed no completely that the blossom never appeared. The same symptoms
were apparent in the case of cherries. Only. a.s they are more productive than
prunes, generally quite a large percentage of the blossoms set fruit. lu pears,
some varieties appeared to be more susceptible than o.ier;,<\nd the difference of
altitude seemed to be directly associated in some casco with lesser or greater
infestation u.' an individual tree. Generally speaking, it was founa at Royal
Oak, at lep.st, that the pear trees situated on low-lying ground sufferen more
than those on higher positions. Apples aa a whole are more robist in their
growth than the other trees just mentioned, and although the infestation on
some varieties, notably King and Baldwin, is mo»t severe, they do not apnear to
suffer to the same extent a^ the other deciduous trees.
Not only does the tb.ips levy a heavy toll on the fruit crop oach by
damage to the fruit buds, but the atroi>hy of these buds, as well as the .iage
buds, caused by the indiscriminate feeding of the insect and its larvse, tends to
check the natural development of tl'c tree. As a consequence, where the
control of the pest is neglected, there is a progressive diminution in the vields
from year to year.
The purpose of this bulletin is to call attention to the damage caused by
this pest in the orchards of Vancouver island, and to the danger of introducing
It into those of the mainland of western and eastern Canada, as well as to
record the results of experimental spraying in its control. At the same time,
new facts concerning the life-history and biology of the species under the
conditions prevailing in Vancouver island are set forth.
' JJ
1-V
10
HISTORICAL.
Known Distribution.
Since the d'scovery and description of the pear thrips in Cnlifomia la 1904
by Miss S. M. Daniel,* the presence of fit species iu other •'art* .,{ the American
continent has been demonstrated. It was not uatil the year 1911 that Parrott'
f u « ^^ thrips (Taeniothrips pyri) in New York state, in pear orchards
of the Hudson valley around Germantown extending from Stuyvesant in the
north to Tivoli in the south. It wps also recorded by him from apple buds at
Geneva, N.Y.
According to Foster and Jones,' the pear thrips was forwarded to them in
May, 1912, by Quamtance of vhe United S*,ates Bureau of Entomology The
specimens were taken in six different orchards at northeast Philadelphia, in tht
state of Pennsylvania.
In the year 1914, Scott* recorded the pear thrips from a small KieflFer pear
orchard near Baltimore, Md. The insect was also taken on some neighbouring
peach and apple trees, though not seriously damaging them.
In Europe, CoUinge collected seve'.l specimens from plum blossoms at
Evesham in Worcestershire, England, which Bagnall' identified as EiUhripa
(JaentMirtps) pyri Dan. Theobald* of the South Eastern Agricultural College,
Wye, Kent, England, pays particular attention to the sne-ies in his Report
on Economic Zoology, for 1910. Williams' records the occurrence of the species
under the name Physothripspyri'D&mel, from Histon near Cambridge, England,
in 1911 and 1913, and also believes that larvae sent from Cirencester belong to
the same species. This author says there can be no doubt but that the thrips
has been present in England for many years, and must occur in many localities.
Mokrzecki' in his report of 1912, published in 1913, refers to the discovery of
the pear thrips on apple and pear trees in the Crimea in March, 1912.
With the exception of these records from the south of England by Bagnall
and Williams, and from the Crimea by Mokrzecki, Taeniothrips inconsequena had
not, up to the time of its discovery in British Columbia in 1915, been found to
occur outside the United States. It is very probable that it will yet be recorded
from other districts on the American continent, for it seems hardly credible that
this insect only exists in localities so widely separated as California and British
Columbia on the one side, and New York, Pennsylvania, and Maryland on the
other. It is feasible to suppose that this markedly discontinuous distribution can
be best explained by the supposition that the insect has been imported from one
continent to another and fro^i one state or province to another on nursery stock.
It canno' be argued that the insect is indigenous to British Columbia, notwith-
standing its discovery on native trees, because it has not so far become established
on the mainland. In the districts already named, certain favourable conditions,
climatic or otherwise, have caused its rapid multiplication to such an extent
that It has overflowed from its cultivated food-plants to native trees where it
has assumed, in some cases, an undeniable economic significance. Especially i?
this true in regard to maples.
-By reason of the fact that on this continent the insect was first found in
California and on pear trees, it is often popularlv designated the " California
pear thrips.*'
Under date of June 6, 1916, a letter was received from Mr. C. B. Williams.
in which he states that the pear thrips must in future be known as Taeniothrips
mconsequens Uzel, as it happens to be identical with an old-known European
species. In a paper* dealing with British Thysanoptera he suggests the probabI<
introduction of the species into the United States of America from Europe in
the larval stage among the soil adhering to the roots of fruit trees.
11
HisTORT Of Species In British Columbia.
D r- ^u "^^u" °^ ^^^^' * prominent orchardist, Mr. T. A. Brydon of Royal Oak,
B.C., had been engaged in spraying his apple and pear trees with lime-sulphur
.s^olution in order to combat " scab ", Venturia pomi Wint, and Venturia pyrina
.\derh. His attention was attracted to the scorched appearance of the buds
on several trees, and concluding that the injury was the result of the treatment,
he at once ceased operations. Later, he observed that both sprayed and
unsprayed trees had a similar damaged appearance which seemed to dispel all
doubts that the hme-sulphur had eau.sed the blighting of tho buds. A com-
munication seeking advice on the subject was straightway sent by the orchardist to
Mr. R. M. WiT!slovv, Provincial Horticulturist, who with his a-ss-istant, Mr W H
Robertson, diseovered specimens of thrips in th.- Brydon orchard. Simultaneously,'
Mr. h. W. White, Field Inspector, acting und«>r the insv ructions of the late Mr.
Ihomas t-unningham, Provincial Inspector of Fruit Pests, also visited this
orchard and found the thrips. Specimens were submitted by Mr. White to
.Mr. R. C. Treherne who tentativdy identified them as pear thrips, Taeniothrips
l>yn Dan. This identification was later corroborated by Mr. S. W. Foster of
California and Mr. J. Douglas Hood of the United States National Museum,
\v ashmgton.
Immediately on receipt of this information, the serious nature of the situa-
tion wa-s reahzea. M the suggestion of Mr. Winslow who proved him If very
energetic in facing the problem, a series of Farmers' Institute meetings was held
in the Saanich peninsula of Vancouver island. Thorough examination of several
orchards was made, and in ever case the presence of the pear thrips was
de. . nstrated. Growers were quickly notified of the importance of the pest,
and ai'yised to busy themselve? in preparing for a campaign of attack during
the sprmg of 1916. Only one treatment for the larval thrips was made during
the season of 1915, and thJg was achieved at Mr. Brj'don's orchard. In the
spring of 1916, another serif of Farmers' Institu' ■ meetings was held, and plans
ivere fully discussed preparatory to adopting measures for mitigating the injury
likely to occur in the following season.
Distribution In British Columbia.
Our investigations have shown that the distribution of the insect is more
extensive than was at first supposed. It has practicallv become established all over
X'ancouver island and the adjacent islands of the Gulf of Georgia, wherever there
lire orchards or maple trees. All the orchards of the Saanich peninsula are more
or less infested, and reports of its presence on Gahriola island have been verified.
Here, too, the maples bordering the shores of the island, showed a great deal of
damage when examined on April 27, 1917. The blossoms had been practically
killed, and the petioles of the blossoms (fig. 14) were badly scarred by reason of
the oviposition of the adults. L^ier in the season these trees developed a very
poor foliage. Even the shade n.aple-trees in the city of Victoria itself have not
escaped, and the few fruit tref s which almost every householder possesses are
suffering from thrips attack. In a thorough search of the district extending
from Victoria in the south to .^anaimo in the north, our efforts were reivarded
by the discovery of the insec* practically everywhere, there being a particulailj
heavy infestation in some o:chards in the vicinity of Duncan.
It would appear that the species has not so far become established on the
tnainla of British Columbia. A large number of the orchards in the Fraser
valley trom Agassiz to New Westminster, including those of Hatzic and Mission,
were carefully examined in 1916 and again in 1917, and although an unidentified
species of Frankliniella was encountered, not a single specimen of the pear
thrips was found. Similarly, a close watch for its occurrence in the orchards
of the Okanagan has so far proveil negative.
36197—3
\
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12
When one realizes the comparatively narrow waters which separate Van-
couver «land from the mainlan.l. and the frequent intercours^ that occ5«
between the two places, it seems difficult to 8up,i,se that the speci^couW n^
be earned to the mamland orchards from the islalTt with nurssry^sS The"2
wlf^h f^f h'*'''"'^' "P^^ l^'' orchardists of the mainland to m^ntain a carS
watch for the species and to report its presence wherever it is found.
SYNONYMY OF THE SPECIES AND ITS SYSTEMATIC POSITION.
Most authors who have dealt with the species have referred it to the eenus
th^^T f"*^'""'^"!'""'.^'^'^- H^*^''" •^°*«^«^ «ta*e« that according to
the laws of nomenclature this name must be replaced because it was first use
to designate a sub-genus substituting the term TAnp,, itself SemDloved
Ih^^a^fh"' ''^^rr ^'""^ ^U^^^- '^*>« ^"t*>°'-' therefore, decid^^t^Te bgate
the pear thrips to the genus Taeniothrips of Amvot and Serville whilst he
i^nJr^"^?//^ "^""T^'^^l '^l'^ previously assi^ed to A'u'a™' among the
K^f. H ^r'^^^K*"""' f*^*'''*"^. Odontothrips, and Frankliliela IniS^
he partly adopted the method of Karny."
Williams' already quoted, originally placed the species in the grnus
Phyaothrips, but this name has now been discarded. ^
THE OrDF.R ThYSANOPTERA.
To, Z^"^ /?''*''''■ ,'^^'^u"K'.'P**''""i^ <livided into two sulwnlers, cuued resnectivelv
Terebrantia and Tubulifera. To the former belongs the pear thrips fig 7^ It jl
distinguished from the second by the fact that the females posset a saw'lke ov
positor, and have the terminal segment of the abdomen conical. The forew nes ar.'
broader and stronger than the hind wings, are beset with numerous SosTopir
spines and have at least one longitudinal vein reaching from the C to t^ •
tip of the wing. Of the two families into which the Terebrantia are divfHp,) A
tKntennT^ '■ ^'^^Thripid. which are distinguished fromThe AeolSri^i i ;
the antennaj being .six to eight segmented, wings usually narrow and po intc
fil J'^^^A "".K ^'•"*' ''^'""*' ^"^' t''^ ovipositor of the femardomi-curvc^
It IS placed m the genu.s Taeniothrips of thi. family because the bodvTs devo i
of retic ilation and the abdomen not closely pubescent; the head nearh or ou
Zlm^Z^'ot'C"'^ V'' "^ '^"« ^"^*'^-^ •'^'t*'''™ the anterior and postS
ocelh, the cheeks swollen, curving abruptly to the strongly protrudinKe™ '
SL fl """fK^'^u^"'"^'"-*;."*"'' ^"h the last two segments (thVstyle short", ■
fa? an 'hnrtU' th '"";"k"T' Pf 'P^.three-segmented. the prothorax ve^' shS
^^J:^.i:tZ^S^£. '--^'^ -"*-' -^ ^ithou^rtalr"!,
Common Names.
ordjTh,'!tmont!;™'"l'i !* f|5"™' ^P''™ as.iimc.1 to any member of il„
13
LIFE-HISTORY.
The Eo« (fig. 1).
I. i.^tT.f^T; K *i * 'if "'"^•"l' ♦!"' e^ " minute, mea«uring0.75 mm. ong by 0.25 mm. 1 roMl.
It i« Blwhtly hean-shapcd and «>mewhat broader anteriorly than po terioriy. It U whiti.h toIouHm
with a very delicate chorion and no evident micmovl.. HnHn. inV,.»...i„- .i.„ ™ ."_""■ .\?i2"n®?J
Period of egg-laying.~Aduh>i wen- first ohserveil to be engaRetl in ovipositinR
about April 18 and contniued to lay their eggs up to about Mav 10, after which
date no female wan seen to ovipost. Xeverthelefss, many stragglers and late
individuals must continue to do so for several days later, which explains in part
the presence of newly-emerged larva? towards the end of Mav. The period of
maximum oviposition extends from April 24 to May 7, during which time the
scars caused by the ovipositor on the petioles of ffuil and leaves, and on the
midribs and veins of the latter become very apparent. Towards the end of
the egg-laying season the under surface of the sepals, especially of apples, receive
a goodly quota of eggs. Isolated cases of oviposition on the young fruit anil
pistiLs were ob.served, more particularly on cherries and prunes, bat it is im-
probable that the resulting damage, if any, seriouslv affects the crop yield.
Jig. 1.— The pear thripti, Taeniollirips ineomfquenii;
oH?». X 93. (Original).
Duration of egg-stagt .—To determine the duration of the egg-stage a scries
of <xi)erin.ents was made. Cages of cylindrical mica-chimneys, fitted at each
end with sleeves of cotton cloth, were drawni over and enclosed individual twigs
t)f apples, i)ears, cherries, and prunes. These had previously been examined and
(It termined to be exempt from punctures containing eggs. Closely-woven cheese-
dot h serves the purpose better than calico which interferes with free aeration,
causing the vapour transpired from the leaves to conden.se on the walls of the cage
and thus rendering observation diflicult. In each experiment a single adult thrips
w.is introduced into the cage and retained there for twenty-four hours, tlie cotton
sleeves being tied securely to the twigs, as.«hown in fig. 2. The adult was then
removed, and the larvffi on emerging from the eggs, were likewi.se removed and
counted.
It is conceivable that weather conditions maj- have some effect in deter-
mining the time of hatching, but it is very probable, as Foster and Jones suggest',
that eggs deposited by the same female on the same day vary as regards their
degree of maturity. At least, we can safely assert that some eggs take longer
than others to hatch, a fact which conditions of temperature alone will not explain
satisfactorily.
The appended table I summarizes the results of the experiments: —
36197— 3J
!• ii
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14
TABLE '-^^y\i^h--^y\^«Sv^OO^^^^^^^ THR.PS.
Vs. -
Dati or
Eiperi-
Nomber of
Halrhed.
DvratioB of
E«8ta».
uDaya.
Avenmf
Mean
Temperature
No.
Ovipositiop.
EmerRpnrp.
Gfwral Weather
rnnditioM.
I
April 21
April 30 . .
5
9
10
12
F.
May 1
" 3
" 4
" «
'* 7
7
15
51
51
52
rhaofmble.
2
4
13
15
53
52
"
2
3
April 23
April 25
April 28
" 29
" 1
" 4
•• 5
9
" 7
" 8
" 10
" 12
" 14
" 13
" 14
" 15
" 5 .
3
7
1
2
3
16
5
6
8
10
6
52
52
52
62
S3
52
14
U
ti
4
9
54
U
4
April 27
2
5
8
10
14
10
54
52
53
April 2fl
May 1
1
2
2
1
3
5
1
3
IS
13
15
17
14
15
16
52
50
^1
51
SO
50
51
It
u
" «
" 7
" 8
•' 10
" 11
" 12
" 10
" 11
" 10
" 12
14
5
51
55
Generally fair.
May '.
" 5
" 7
29
24
5
1
4
2
4
5
2
0
7
9
10
11
7
8
5
7
S3
53
51
SO
50
49
48
4«
46
Fair to changeable.
11
u
ChanffPable.
" 7
" 9
" 9
" 16
" 17
" 16
" 18
" 15
" 18
" 17
" 18
2
1
1
3
19
5
21
17
7
9
10
9
9
6
7
8
9
47
49
50
49
52
49
49
50
51
HhaiKjeable to fair.
u
Generally fair.
u
tt
KivcnTiabTn'!*' ■"'■""""" •*'»'««•»'«' P"-vailing during the period of incubation of the ,
h
15
TABLE II.-MAXIMl AND MINIMUM TEMPERATl'RES DIRINO THE PFRinn OF
INCUBATION OF THE EGO« OF THE PEAR THRIP8 AT ROYAL OAK
VANCOUVER ISLAND, B.C., I»l«.
•thrr
oiu.
Datp.
•able.
April 10
" 11
•• 12
•' 13.
" 14.
•' I».
" 1«.
" 17.
• 18.
" 19.
" 20.
•' 21.
" 22.
" 23
'• 24.
" 28.
•' 26.
•' 27.
'• 28.
•• 2«.
" 30.
Maximum
Temperaturp
•K.
S8
52
.«)
62
l»
.■;«
«o
SI
S2
S4
S8
S4
55
.57
60
65
62
61
.59
64
68
Minimum
Temperature.
°K.
42
42
3H
42
44
.•w
36
42
39
33
.•w
;i9
39
:<w
43
43
46
42
44
4U
36
M»'
Datr.
1
2
3
4
5
6
7
K
9
10
11
12
13
14.
15
16
17
18
19
20
21
Maximum
Temperature.
Minimum
Temperature.
'V.
•F.
68
39
72
40
73
51
67
48
64
44
.5.5
38
.53
39
.55
41
53
.38
.58
34
60
31
62
.32
6S
34
74
37
74
41
72
44
«7
48
67
43
67
43
63
44
68
.13
(air.
r^i.^
•-.-^.^
tf
fia. 2.— Mipa-ihinmey rage in position on a p<ar twig aa u«'d in oviposition cxp-ri-
mc-nts with the pear thrips. (Or'uinal).
Egg capacity of adult.— In ordiT to (Ictcrminc how many eggs a single
iulult pear thrips may lay, a serios of experiments wa.s untiertaken. Mica eaRea
(hg. 2), fitted at each end with a cotton sleeve, were securely fastened to branched
of the trees, enclosing one or more buds. In must cases onlv a single bud was
selected and the others removed. It was found that as the bud developed
the thrips had been provided with ample food as well as sufficient surface on
w-hich to oviposit. The experiments were commenced and the mica-cages
placed in position l>efore the adults had emerged from the soil, thus en&urmg
that no eggs could be laid by individuals other than those intro<luced into the
cages. Further, the insects n ' the experiments were trapped as they
emerged from the soil so tha. aid not possibly have commenced ovioiv-
sition before the experiments . i.,
n
16
The varieties of trees uwd in the experiments included apple, pear, eherrv
S"/^; ''.'S.i?™T- Ik '""'*' ,'"^. *.*',* experiment was c.ntinued until the death
?i il •♦hK'T,,^''^- *"'"'"^ bl.«8oms and leaves were carefully examined
for eggs with the followmg results:— *»miuru
TABLE III.-NrMBER OF EGOS PER INDIVIDUAL ADULT, AT ROV\L OAK
VANCOUVER I8L.\ND. B.C., MARCH 27 TO MAY 29.
Nuin>KT o(
Eipprimeat.
I
2
3
4
5.
a.
7..
8..
9..
10..
P .
12.
13..
14..
IS..
16..
17..
18.
19..
Variety of Tiw.
Numlicr of
I-«Rs.
DurhrM apple
Gravriutpiu '
Red Cheek '
Bartlett pear..
Bosc
Olivet cheiT>-.
as
118
109
42
127
98
91
113
112
liO
4
153
128
113
112
63
49
49
120
Ntt '< .r of
E«pi' iieni.
20
21.
22.
23.
24
25.
26
27.
28.
29
30.
31.
32
.^•^.
34
M
38.
37..
38..
Variety of Tree.
Numlier of
Erich.
Olivet ehcrry.
Italian prune.
Columbia plum.
Bartlett p<«r..
37
7
108
M
42
18
120
12S
37
4«
90
27
28
93
78
9
4
27
32
.In,, r* ^ ?K ^l"y fu^ "^t^""^ ^^"^ b"^ was a blo8sora-bud, more eKiw were
deposited than where the enclosed bud was a leaf one. The pear thrips^ows a
decKled predilection for the blossom pedicels as receptacles fo^r Hs egX
♦ h« J„if T "u °^®?f^ '*"* ^5' ^ ^'"K^« individual varies. In the experiment
the highest number laid by any one was 153 eggs, and the lowest w J4 Und.T
Z7m\riTlT^N'- P-^,t that t^ pear thripsTscaSe of laving
manv is fhU Th!*' ^ "* '* " "'^t ''^''•y that every individual actually lav.s so
manj as this The average, as calculated from the above table, is 73 but this
may be considered lower than normal '
8ake^oTlmniri!nn°"Tl*^^ °^"*^' ""^ ^5 mature specimens was made for the
t^be. fivp nn 1T"m^^ -^T^ '" *. P^'^*^ "'K'^n consisting of ten ovarian
tubes, five on each side, united posterioriy to form the oviduct. The oviducts
of each side again unite to form the common oviduct opening to the ex orior
S-cXanteSv"wh""' about twenty eggs besides^umVous immlure
?a™v bv d^tluX) 7 1 *^^ *" •'^•'' ^'-^ ''"ach-d to the walls of the bodv
cavit> t)> delicate fibres of connective tissue. Normally, theref-.re the fullv
deve'fpS.''""'^ ""'' "'*'•" ''' '"'^- '^'•°"* 200 egg^ 'at variou^' lil^lfsf
tl.P Sk^ **''' ^^'"^ "^ oviposition and, indeed, throughout the whole snrimr
rimX I °"< ^»"/'«".v«'J island i« frequently verv uncertain. Temperatures
Srd XZJV A,..^?""'h'' 1 '^' P-vailink, cold, southS wlX
hr^llitnt c. K- °t April and early m May matters improve considerablv
bnlhant sunshme prev.^iling during the day, and the teni,>erature ascending to
It will l)e readily seen on consulting table I on page 14 that no strict corre
heTgrtThatcl'VoSr the air-temperatures''a'nd the timeTrec'utdTor
Hz t* : . "o"Knly speaking, the period of incubation varies as tho
rise of temperature but by no means proportionallv. It may be t»,at embedded
fnfl!^^ Tk'^^T^^^^ the epidermis in the plant tissue, the eggs are not readd
influenced by changes of atmospheric temperature '
17
The Larva (tigH. 3 and 4).
De»eription.—TMter ant" Jonm' have given a complete deMcription of the
ZU^t. 7 II i'*,*"'"''^**' 1"«t«*- T*"' *l*^'-"Pt'«n of the pupa and the adult,
which follow later, are also borrowetl from the same source.
" Fiaar 8taoi (Labva 1 dat old).— Lenath 0't46 mm- width nf h«ul n im ...«. —lAti. i
I ^1 ".ij' Jl^i 'lill* "• '^' '?" "• 'i™'-™' «>'»uf . «nin«lur,-nt white; wnoraUhmpe. (uiiforai Tfl(*M»
hc«.l. and leg! I«ne in proportion to the rMit of the hody. ami unwie dy AntonMdi.ti.Mlv ^
...ented, fi"t ««n,«t .Lrt. cylimirical ««,Bd «,m™, about ?w*;r..*i„„i"^fiSt o^S ij,^„^
third ■c«ment»TMchtly lon«er than wond. unmhaped; fourth alwut a. lon« " w«t o?iSiu t^SSJI'
iiTBtely conical A few very fine coni.piru<m. hair* pre«-nt on all jo"t, mo" ^minint on^!S,«t
aT; """^ •ubou^ln.te: eye. reddioli hrown. Thorax about a» loni a, LM^«^^ilhUv^«
Abdomeagnw^ually taper B«, !0*itment..l, fir»t eUht ««ment. m\>^»^. l\^^ x^^lZJ^'^L
.ibniptly taperuw. with a frinne of lo-g. white. n.Mirly incoS.picuou.hairiL.-m ««it fe^ !Sd tTS
newly equal >» lenirth; tarn oac ointed. ending in % .in«lc Clack claw." In SdhSn U T^t?.^ VhS
a nn« of .mall denticle, i. provided on the pcMterio ma^n of the ninth «-i,n?nt of the aW^Tmr^
k
Ml'
;
). ' I
V. ' I
Flo. 3.— The pear thrii- . Tirniiilkriit.^
iHcoHseqwriK: lar\-a recently emenciMl
from theeKK, ventral aspect, x 200.
(Orifdnnl).
0 l08-t*'mm''?e^*h'''f*"'':t''''""n'-.oV;''^'*'~T"''»' '<■'"«*' ' »«3 mm; Icnifth ..f head 01.5 mm: width
1083 mm, length of prothorax OVm mm, width 0-2186 mm; lenRth of mesothorai 0-18.^1 mm width
J^nKth of antenna; 0 2833 mm: seament I, 26 u. II, .W u. Ill, 76 u; IV. 66 «.- V. 14 u; VI,
II 466 nun.
10 J,- VII, 33 u.
aliout
narrow
cylindrical
M lnn„«« I =»^ t''^; »KI"'^nt.i; short, cylindrical: II, obtuse, spindle-shaped: III. spindle-shaped,
, „!!J??it^ ^ .""V-T *?»'*'"''•: iV , nearly as Ions a-i HI, broader than the rest, subcortical : V, short,
cvlinHrie?! AM- •'..'• °''*'"''-^'^"V''';''°'' ^"'^" *•>■"- '''• VII, twice ,» l,.ng as VI. narrower and
V,. InwiLh =,Ki. ' ul *"">«Vf rsely striated and with a few inconspicuous wiiite hairs. General colour faintly
i, .-ulm?-?.!^]?!. ' °''*M«'Iy fusiform m shape. B,Hly lonRitudimilly and luterally f.untly striated. Head
1 rna-nlr;.! -^ Jif" *• ^f'^ reddish brown, situated a little in ailvancc of th< middle; mouth cone
'■™„?!;^.k'^'. ,"•*'■'/ as, long as the head, extcnilinn to the middle of the prostemum. Prothorax
» '^ j'Ji"'"""^*' '^^^ reddish brown, situated a little in ailvancc of tht middle; mouth cone
'-inrn tH^.K '-." 1?' as long as the head, extcniling to the middle of the prostemum. Prothorax
•w^e J^H» "'i ^"u" '"»*<.. <^'/trt!"i!< P<«teriorly. Mesothorax anil mctathorai short and broad,
10.«.om»I?.i ?? y' "'•>«'l"al. "> 'enirth about as long as prothorax. Abdomen broad, gently rounded.
I,m!^r ITiJ^i: "P^™* at segments V ar.rl VI; first eight segments subequal; segment IX distinctly
«DiS™' *hr.!S* J?^' , posterior edge armed with a circle of strong, short, thick. wedRe-shaped
not n,,;t» .. I ""'"'W'o"*' and me<Iiovcntral ones shorter and smaller: segment X slightly tapenng,
SDic,?™,. Jf:. ■? ^ ««n>.e?t IX. Lateral edges of abdomen finely serrated, also with a few long, incon-
emml- t.~i "»'?•«;'>"'•> are more prominent on segment X. Legs strong; femora and tibiiB about
iquai, tarsi, one .jointed, ending in a single black claw."
i:
•r
Id
^i
18
haf.i!^'"^"'" "( '«."'«' «(«l/«—App<'aring first about May 1, when the newl^
S? f'^'r ^^"^ ^^J activities, larvjB remain on the tr^8 until about tj
middle of June. Immediately on emerging from the egg the larva Ss
move slowly around as ,f taking stock of its surroundings. Aftir a Xrt btSv
uIZ'^ the vegetable tissue with its mouth stylets and begins to suck up t
liberated plant juices. Consequently, by reason of the compafative transpar^enc
of the small individual one can observe t^,, alimentary canSl ijaduallv Zum^n
?e5«1?*'°* '*"'•**' ^^' imbibition of the green chloroplLtT As thrS
feeds It increases m size; the original cuticle proves too small and is shed
hirth r* "^ "l^^^ifi^^^ ?'«* "°"'* «<'<'»'^' in ««nie cases, two days' afte
Xt Th*p° W l*^^ T* ," '"^l" *? "•«*»» ^l^y" «'d before this moult tak
fn„nfi.„7 ^ '••"" l&^ along the dorsal median line, the larva reniainin
inactive for some time before this happens. The legs and antennte are «^l^^mn
withdrawn, and finally the body is extracted from^the old sheath. During th
Via. 4— Thp pear thrips, Tofnialhript
tncoiuequena: rull-Kn>wn larva, doraul
aspect. I 90. (Original).
process the original tarsal claws servo as organs of fixation ombeddpH in H,.
i^,i , • 1 1 "^® . *"*^ second stadium are robust and verv active How, A
«»,; A- ^'u'' ':'^"i'"Pfi for the development of the larva varies Normallv t lo
dur^^lth ^^"-^ *\Tnr*''"'^ ^'"t '«^ temperatures such as were exSi. I
during the spring of 1916, and especially from May 6 to May 12, when the m
fh^tSKSr^/Xtrv^'.*-'' ^" -'-' «--^ b/exertingV5h5 .i.'
xs
19
When mature, the larvae, now as large and sometimes larger than the adults,
cease to feed and abandon the foliage for the soil, which they enter by any
convenient crack or small aperture. The method of transit from tree ground
IS rarely, if at all, voluntary. Instead of crawling down the branches and trunk,
the larvae merely fall down. Strong winds and dashing rains remove a goodly
number, and many, again, are carried within the old, falling calyces. It is
stated, by one authority at least', that those individuals which fall off the trees
when they have only partially developed, mostly perish, unless they can attain
to full growth by feedmg on weeds or grasses lieneath the trees. Necessarily
such immature larvae would succumb in cultivated orchards. This appears to
corroborate a similar statement made by Moulton." In an examination of a
.small neglected orchard at Royal Oak, overrun by weeds and grasses, on June 2
several larvae were found feeding on gra.s8?s. They had dropped from the
overhanging leaves of cherry and apple trees. This would seem to discredit
the idea entertained by some orchardists that it is advantageous to leave orchards
m sod because of the difficulty which the larval thrips experience in working
their way into grass-covered soil This view is evidentiv more imaginary than
real, if one will only stop to consider the small size of these insects and the facility
with which they can avail themselves of the most minute opening. When,
added to this fact, one realizes that weeds and grasses offer sufficient nutriment
f(ir undeveloped larvae to become fully fed, the argument for cultivated orchards
seems to be strengthened beyond measure. Further, a series of experiments
conducted by Moulton, has demonstrated the value of ploughing and cultivating
as partial remedial measures in ridding the top layers of soil of the pupa. The
protecting earthen cells are destroyed, and the contained pupa are either injured
or killed. Since, however, many larva; penetrate beyonvl the depth to which deep
ploughing can be practically carried out, this means of controlling thrips in
orchards is not by any nieuus infallible or absolute. It has been observed, at
Royal Oak, that .some larva" will, indeed, penetrate to a depth of lo to 16 inches.
Further, it has been shown that with the chuss of soil with which we have had
to deal, the loose mulch of four or five inches generallv contains comparatively
few larvae.
Larva>, after leaving the trees about the middle of June, remain dormant in the
soil until September or ()ctoi)er, a period of from three to four months. Th«^
I)repupal condition is then assumed. In California, the average time of mh-%
terranean larval existence is .stated by Foster and Jones' to be from five to six
months, with a minimum of two and a maximum of eight months. Neither of
these extremes was experienced on Vancouver island, where no larvie were
found after October 3.
li^'
I
.
If
DEPTH OF LAKV.E IN THE (JHOIND.
After the larva; have penetrated the soil and found a suitable place in which
to rest, they make for themselves a small oval cell, the inner walls of which are
smooth and compacted. Doubtless the cell is fashioned by the active, rotatory
movement of the abdomen in a manner characteristic of the pupae of many
( oleoptera and Lepidoptera. The length of the interior is approximatelv 2 mm.,
and the breadth about 1-5 mm. Here the transformations from larva to pupa
and pupa to adult occur. The adults continue to occupy their cells in safety
until the warmth of spring stirs them into activity.
The distance to which the larvte descend in the .soil depends on the structure
and texture of the latter. It is to be expected that in an open, porous soil
characterized by thorough breathing, the larv* will penetrate deeply, whereas
in a clayey, compacted soil, the mechanical difficulties to be encountered as well as
a diminished circulation of atmospheric oxygen, will tend to confine the larger
numbers to the strata just beneath the surface. Again, where the surface is
covered over by a thick sod, the thrips may be generally found among the grasa
roots, not deeper than one to three inches.
36197—4
t, : .
i ii
I r
20
orrhi^Ti'J^p^®^®!' A°u ¥'"° '"i ^?^^' measured samples of soil taken from the
orchard at Royal Oak, beneath the trees, were examined reimlartv throuSio^t
the summer and autumn from July to NoUmber. Very flw^S were foun,
^l'l\''£Lf ® *°. ^° '"'^^^l t'''^ °°°« ''^ "» '° the 1 Jse s^SfmSch Th
soil IS a tenacious clay, and below 10 inches is scarcely penetrable In ihl
rumm;r'hv ^t'^"''H*'"''^ by its capacity for retaining mTsture and, n tt
summer, by its tendency to bake hard under the heat of the sun.
The Prepupa (fig. 5).
0 6W mm; width 0-383 mm 'SW .LSar ta'J.U ,J?i„T'P*''°J" 0-35 mm; length of abdomen
brown. Head «ubquadrate7kbout m bm^ J^ln^ ' «''°'"-. t™5»l!'cent white, deeply tinted with
rounded, extendinito abSut one^hllf leSThtf^roXnum An^.i:^'*"'^ ^'^'^u """th^"" broadly
of head, apparently four-jointed; firet three ^^^^pili„ „,£!^"? ^^f*"!'?* bf^kw*"! on each side
thick and unwieldy; segment IV atoutMl^S^reZi^L~^"^ ,"'•»!«*»', about aa broad as lon«,
pint Antenn« withTfcw iicoMpJcuo" whftc S S^.t°„«,'' "'"'^'''5* "^^ **^"»« *" »° °^^^
broadly rounded posteriorly. Me3(™ hm^^r- ^U ™5P* u "^ Pf"'^ ^V^ " 'o"* »» the head,
to distal edge of third aMomiMf«SS^„t AM^^e^l'S^^^.lJi''"^^^^
gradually tapering from their Mter^vFi^t.?JhfJ^:?^*''\f^' ^"'?** »* "^ "><* IV. segments
of IX with b^d spines somewhat siS to h^*f L^'j;!^.'''''''''''. \^^ ^ ^°J^'- dii^J end
.tout, s.mil„ to those of full^wn I'^r.^, X^^y'^^ ii^Xi^^^^X^t;^:^:^.]^^
Vig. 5.— The pear thrips, Taeniathript
tneoiuequeiu; pupa, first sta<?e,
dorsal aspect.XlOO. (Original).
oil eiiner siae of the body as far as the th rd and fourth abdominal spirmo.,
21
r» . I" ^?}^' ^^ ^'^^ prepupa was found on September 13, and the last on
October 10. The avera,ge period spent by the individual as a prepupa is about
one week to ten days, when the skin is again moulted. The insect then develops
mto the true pupa. *^
The Pupa (fig. 6).
DMCBimoN "(Second 8TAGI!).— Total length 1 418mm: lenirthofhead 018.1mm- wiHfhn 1M.«— .
Wml-TdihT4?«*mm'"'"4h**'**'' "-P """.i f"^'^. "' "■'■^ho4x 0 3.? mmTTe'n^h o^fVbdom?,^
0'783 mm; width 0-418 mm. Shape similar to adult which is visihlp hpnpnth »ho fhio ♦™«.^~-»^.i, ii
Apparently brownish in ,»Jc„r caused by adult within. H^ld b^Wcr U^ on^^ejt la^ST^^^^
^uth-cone of adult within «tond.n« to posterior .nlge o( prothorai. AntennS la^ cumbe^me iTd
back on the head and extending past middle o( prothorax, four-jointed: I, short; II. elbowed ™uttwiM
^.'?!^.™= 'V- '/■?"; cylindrical; IV longer than III, sides uneven as knottk clubTntly ta^riSl to
vS* ffT'. •'°"'* ' "' -"" !'•'" ""?*■ ] ?' PMP". "int n of adult in joint II of puparand iS o( iSuU
^„*,^ti„J.''nK''?^ remaining joints of adult within IV of pupa; three ir four white^irnspinioSs hSi^i
projecting cophalad from elbow on joint II. Prothorax br<Mulcr than long. .Mesothorax aboutone wd
one-half times as broajl as prothorax. Wing-pads extending to distal margin of eighth al3om^l g^™t
fore pair not quite so far. Abdomen widest at third ami fourth segmenls, tap.-rin« from there ^tuse
apex. Po« erior edge on ventral side of segn.ent IX with four strong spine, n-sembling a meaffork This
IS apparently the cremaster. Legs sU.u. Entire bo<ly with numerous, inconspicuous Xte h^ira"
nici 1-
Fig. 6. — The pear thrips, Tiirmnlhripii ineim-
eequens; pupa. siH'ond stave, dormi
aspect. X 100. (OriginnI).
Duration of pupal stage.— The fir.xt pupa; are found about the middle
ot heptemher and the last about the l«>ginning of November, so that the total
period covered by the pupal stage lasts for si.x weeks to two months. In certain
seasons and under unfavourable conditions, it may extend for a longer time
than this, but it is interesting to note that there appears to be a much greater
uniformity in the duration of the various phases of the life-historv in Vancouver
Island as compared to California. Foster and Jones' state that the earliest
pup® are found in the month of May in the Santa Clara valley, but these they
consider as developing from premature larvae, the precocity of which has been
determined by infection with some fungous organism. Their latest pupte are
found in December, with the maximum number appearing in October. This
latter month also represents the period of maximum pupation in Vancouver
island.
!
j
'!' i
if
m !1
22
«♦», ^*,T"'.** ^*^* ''^° reasonable to suppose that pupation would have been
I^e'mor?:<;Sabl"'''Z' ^vh' *^" '" '^^*"'°™''^ "'^^^^ ^^^ ^'^"'"^ '-^itbns
are more equable. Our evidence, however, goes to prove that such is annar
ently not the case, at least not to any marked extent ^^
in the middle of June when the larvte were full-fed ind fRllmo. f,^^ tu^
S'finX x'r rv^^''" "^^^ «pe-aiiy cot^VuctrioJe^^^^^^^^^^
with finely sifted soil. The larvae burrowed beneath the surface iust ^
they would do in the orchard. The boxes were then buried "n the ZLd
with thtir tops level with the surface, in the yard adjoining the labSrv
tTi. Zlu """"^ *''"' •'^Pf ""^^' «''»««* "'^t"'"' conditions* From time to
time small samples were taken from these boxes, and table IV show™ the com
5^IO^oTotmtr'Tr9,r'^ ""' ^^"'^^ ^' "'>^^' ^'^•^ au?n7thfperd-
-^'
Fig. 7.— The pi-ar -hrips. Taeaiothrips ineimsequenx adult
winK.s,mtspipad. ,X9S. (Original).
T.VHI.K IV
I
KNV.rrXv"M'i.LKs"'Rl>^YL'o'V
NOVKMHKR. 1«I7 ■ ^'^^'^"^^'^''* '-^LAND, B.C., DURINC; .III.Y To
Sample .utnhiTs.
I to 8...
9 to 18..
int.>:6.
Dates I'xatnini'd.
luly 10— Si'pi. 10
Sept. I:J— Oct. 2
I
Oct. a— Nov. 3 i
I..^KV.t:.
N'uiiiImt
32
33
I
I'or rent.
100
16
0-7
Pi p.B.
Number. Pi>rccnt.
77
Adiltm.
Numlx-r. Perfvnt
0 0
84 I 0
.M'8 I 53
0
0
405
The Adult (Fig. 7).
02 mm;wXh'-:f"iurtLl'Sl":'^"'"WidTh'\^^ length of pro. hora. 013 mm; width
I^iiKth o( antonnal «r«n. "nt": f 33 « n 45\r 111 M i- ?v il''" v li "T.' '"»"' '"Wh l-2fl mm.
total, 0 31 „,„,. Cohmr dark Im.wn tan, I ihi ^2Jni ^ "ii ^' ^'iJ' X'' ■?«."• ^'"' » "• VHI. 12 u:
ohe.kHan.h.d.antoriorn.arginan^LT.^.iX./taVirr^^^'L'iria,."^^^^^^^^^^^
■^--^,
23
f; 1'
"^v'i^i'.°iL^J^'^ '""* P™™"«">t "P'™-* >*etween poxterior ocelli. Eyes prominent, oval in outline, black
with light borders. coar««ly facetted and pilose. Ocelli approiimate. yellow, marnihed inwardly with
orange-brown crescents, the posterior one- approximate to. but not continguous with, light inner borders
1^";^"^"*''^°'* '"V*'^- *'f»*^ *."*' ^^'^^' •""""•'"■y P»Ipi thr«-8egmented; labial palpi Two-
segmented, basal *gment very short. Antenme .ight-^^niiiented, alx.ut two and on^half tin^s as long
T^-^"" '?™ •'«*». "ceptsegmen III. whirl; is light brown; spines pale; a forked sense-cone Z
h TtiH , .1? "r*'"/'"* "'• *'*•? » »""''»[ ""•• "9 ventral side of segment IV. Prothon.s about as long
but wider than head: a weak spine at each anterior and two large, strong oney on each wsterior angle-
other spines not conspicuous. Mesothorax with sides evenly '.nvex, angles ro mdnj; metanotal pUite
with four spines near front edge, inner pair largest. The mesonotal and metan.-.al plates are aintly
struite. Legs moderfttely long, uniform brown except tibia; and tarsi, whi.h are yellow. .Spine, on tip
?/„„r.K!l„J^ L.!" ,.' ^'"'^\ '*""^ "P'."'"" "" hind tibi«. Wings present, extending beyond
ip of abdomen, about twelve times as long as wide, po^ ,t.^I at tips; cost.* of f .rewings thickly set with
from 28 to 33 quite long spines; fore vein with 12 to 15arrange<l in twognups .f 3 andB respectively, on
basal half of wing and a few scattering ones on distal part ; hind vein with l.>or 16 regularly pUced spiiw
Z^U^yfZ^l""' .T'"""^;;* *"■"''■ *','•*"* »* '■"•"»' ""'"••"■ -^hdomcn subovate. tapcnng ab?upty
TO^tive tiiSul "low" ««'"«''«: longest spines on i«-gments 9 and 10: abdomen uniform brown;
In comparing the wings of a large number of adults, it is found that there
IS a greater variation in the number and disposition of the alar spines than is
stated by Foster and Jones in their description above. For instance, the
number on the costal vein varies from twenty-three to thirty-two on the fore-
vein from twelve to eighteen. An examination of 100 wings showed that 59
per cent had the basal spines of the fore-vein arranged in two groups of three
and SIX. The first group of three appears to be stable, but the second varies
from four to eight. The spines on the hind vein vary from twelve to eighteen.
Duration of adult stage.— The total period of aerial adult activity extends
from about two to two and a half months. The numbers increase to a maximum
depending on the rapidity with which their emergence from the soil proceeds
Gradually a diminution begins until, after eight to ten weeks, only a few stragglers
remain on the trees. This season's records show that the adults first began
to appear in the last days of March and to disappear at the end of May, a few
remaining over into the first days of June. It is doubtful whether these late
individuals lay any eggs. At least, none o/ them were observed to oviposit
It must be remembered that adults are to be found in the soil for a considerable
time previous to their appearance on the trees. Most of the pupse have probably
transformed to the imaginal condition in the autumn and early winter. For
a period varying from one to five months, with an average of possibly three,
they remain inactive in their subterranean cello until conditions are such as
to favor their migration to the upper a=-.
LONGEV Y OF ADUI-TS IN CAPTIVITY.
In captivity and witl .od inside the laboratory, adult thrips do not
live longer than four days < average. Among large numbers thus confined
individual specimens have !< d as long as eight days and, in one instance,
ten days. If supplied with food, .some will live as long as twcntv days, a result
which was repeatedly obtained by confining a number of adults in large glass
vials with maple buds, their escape being prevente' by a muslin cover which
allowed aeration sufficient to obviate the collection of moisture on the walls
of the tube. In the field, adults imprisoned in mica-chimneys fixed on the
trees lived for as long as four weeks. It may be inferred, therefore, that under
natural conditions the duration of the adult's life would probably cuvit a period
of about four to six weeks.
IS'I
■i:l
.W
M-
ft
fy
\ t!l
24
'N-
TABLE V.-LOx\GEVlTY OF ADLLTS IX
TA^s'^'^a^ii^'^S l.ir'"' '^""•^^ ««'ECIMKXS
NumlMT (u"
Kxperiiiirnt.
1
2
3
4
5
li
8
9.
10
n.
12.
NuriitMTof
Spipjmons.
^ Datp of
DtiN-of Dcuthof
1 onfinpiiipnl i Last
Spocimcna.
Lenirth of
Life of
TionKest-livcd
iSpocimens
in Days.
50
Murc-h 29
April 2
4
30
" 30
3
4
6
10
5
9
S
g
43
.«
46
2S
119
116
" 31
" 31
April 1
1
" 2
" 2
6
" 10
(I
;; 10
" li)
23
3
10
76
4
" 11
S6
54
S
" 7
" 10
12
5
5
jwlSa^'JdwB
case survived fron, April 20'Slay to, a^J^rioTrtSS S"'"' '" '"''''
MIGRATION OF ADILTS FROM THE SOIL TO THE TREE.
s.;.iSr;^iqj;i' iir-ffS,,;:^ 5S:: ,:;■ ™r r'^sis, rt,^
with hnlliant sunshine, an air teinnerature of ^2 Zir«l" ir i ' . \^^^''
iBi
25
This may be repeated several times before the animal embarks with a spring
from the surface on which it is resting. The legs appear to assif.t in this initial
movement of propulsion. As the adults settle after a flight, the wings are
immediately tucked in and arranged straight along the abdomen, parallel
almost to the mid-dorsal line, the anterior wing of each pair covering the
posterior one.
That there is an undoubted migration of thrips from one variety of fruit
tree to another is well borne out by facts. Thus, swarming from the soil was
practically finished by April 12 at a time when the buds of Fluchess, Gravenstein
:ind Red Astrachan apples were in a receptive condition. At this date there were
practically no thrips (m the King and Wealthy varieties, their buds being as yet
tightly closed. Later, as their l)uds open, the migration becomes more evenly
distributed throughout a mixed orchard, indicating a migraticm from early to
lute varieties. The same phenomenon applies to pears, of which, in the particu-
lar orchard under observation, the Bartlett buds are the earliest to open and
arc therefore first attacked, followe<l by the Bosc. Jules (luyot, Rivers' Princess
and Louise Bonne. Of course, the migration takes place from apple to pear
ill tlie same way as from ai)i)le to apple, or pear to i)ear.
I- M
Flo. 8.— Uufhoss apple buds. May 3, 1917. -Viiult pear thripa
may bo st'cn on thf bud on the right-hand side. (Orininal).
Prunes, plums, and cherries, in virtue of their later development than
apples and pears, are the last to be attacked, and the season is often well advanced
licfore the cherry buds become infested. In the case of prunes and plums, very
lareful watch is necessary, as the presence of only two or three thrips inside
the small and tender l)uds will often mean their total destruction.
DKTERMINATION OK THK D.\TE OF .\PPE.\RA.\CE OF THE FIRST THRIPS AND
THE NUMBERS EMERGINti FROM THE SOIL.
The growers make the ac(|uaintance of the pear thrips in early spring,
when the adults emerge from their hibernating quarters in the soil and make
their way to the bursting buds (fig. 8).
3
If
}t4
36
to «et,n atViVL^'SSl'^ie I^ST^ZT ^ Gent' T^ ^"^"^'
somewhat earlier; but, nevertheless, the Lt aduTs Ue oierved i^X" ZTl
r^rWl^f 1 • t™P-'"«g«'«- Emergence continued until AprU 27 with ^
period of maximum emergence lasting from April 2 to April 13 I
square, and the depth was exactl^wZ Th» the boxes was exactly 2 f. .
in the soil some 6 inehT whilst the^n;«7.**"P^" *°P "^^ '"^^'t^d »"«• >*»"■
cross slats, 2rches wide bv fivliv^hl 1 »'o«om was re-enforced with thr.
tances of 6 inches apaJt Eachtllf wf °^ ^""T} ^-^tP' P'**"^^ «»* ^q"«' -i
diameter, which also'^erforatSthtboTt^m'''^^^^^^^ °'" '^ ""
fitted with a closely fitting cylinder of Hn ?L fm^i ^^^^ *'?'^' *8^'»- "
with a narrow flanite one^iiZh ^f „„ • u ^u*' ^9^' ^* '"'^''^^ d*"*"?- Provid.
the hole. Cide Xs cvSf a ?fn n J"'^ '^1°''^' *" fPP"^ the cylind.T ,
basal margin. The apS Unerture nfTh" "^ ^^' '^™^ '^'^'K*'' ^^^ fi'ted t., r-
27
nullifying the escape of the thrips once they had reached the tul)e8. As well
a« bemg an accurate mdex of the period of emergence, the counts obtaineil by
the use of these trap-cages represented the actual number of thrips that were
present in the two square feet of soil covered by the boxes n^Z
The average of the numbers emerging in six boxes throughout the orchard
represented roughly the degree of infestation of thrips in the soil. As a method
of assistmg the orehardist m his operations, no better plan than these trap-
cages could be employed for determining accurately the first appearance of the
thrips at the beginning of the season. Necessarily, the boxes mu.st be stoutly
ma<le, and all possibility of cracks, even the most minute, eliminated
Fig. 10.— ( 'ombined trap-rnno nn<l ry lindcr of tin used
for holdinK the Rla8.>i vials, and fitted into
the holes of the soil cmergenre-hoxes, in
the orchard at Royal Oak. Vancouver
island. X 2. (Original).
1 h 'Ti f ''^^•"■**** apparatus consisting of an inverted, cone-shaped, muslin
i)ag (hg. 11), suspended from an overhanging branch, will be found to provide
an excellent indication to the orehardist of the first emergence of the thrips.
Ihe lower margin is provided with a circular piece of stout iron wire, which
serves to keep the bag extended. Sods are placed firmlv around the base
m order to keep it in position and to prevent the escape of the insects. The
whole apparatus is nothing more or less than an in.sect-coUecting net made of
stout, close-meshed muslin. It should be examined every day for the presence
of adult thrips, then turned inside out, shaken, and replaced in its former
position. Thus the orehardist will obtain a fairly accurate idea of the daily
increase or decrea.se in the numbers emerging, and will he enabled to decide
the period of maximum emergence. For obtaining efficient results, these traps
should be established in the orchards about the middle of March.
In table VI is represented the actual numbers of thrips emerging from
the 'joil and trapped in each of six boxes distributed through the orchard at
Royal Oak, Vancouver island, B.C. It will be readily seen that the largest
numbers appeared between the dates of April 2 and April 13.
-J' !
M'
4' .
!
t
1
i J
28
^^ \
TABLE VI
. ;,- BOXKS PARTLY
ANCOUVER ISLAND,
29
EMERGKNCE OF ADILT8 IN HELATION TO TEMPERATIRE.
The records for the years 191G and 1917 go to prove that the critical
temperatures which determine the emergence of the adults from the soil in the
spring, are 45 degrees Fahr. for the soil and 50 degrees Fahr. for the air. Should
the temperature at any time fall below these figures after the emergence has
aetually commenced, the effect will he to delay the process and to give a double
or treble maximum to the curve of emergence. On the other hand, should the
temperature Ije maintained above the critical point for some time, a graphical
representation of the emergence will show l)ut one maximum.
'i?
Fig, 12, — Straight-liiif cun-t- showiiw cmrrKcnrr of aduit p«ar tliiip:, m trap ciwea
under trees in onlmrd, Royal Oak. Vancouver island, March 2S-April 25.
Dotted cur\-e is a graphical representation of the average daily mean
soil temperature during the same perio;i. ((Jrii?inal).
It will be observed that the curve of emergence for 1917 at Royal Oak,
Vancouver island, B.C. (fig. 12) has three distinct phases, between the
dates of March 4 to 10, due to the variations of soil temperature. On
March 5, 7, and 9, the emergence was notal)le by reason of the large
numbers which deserted the soil when the temperature rose above the
■ .
h.
i"
n
13
m
30
On the whole, thrproc^ wa^ markp.l wif' fal below 45 degreoH Fahr.
hen enier«ng in a ?S^ coC^rine JixL/ H «P«d>ty. the greatest num-
after whicK tLre waTr^aS aLS nffln^' ^'T ^^''"'^. ^ *« ^pril 13.
was completed on Aoril 28 Th„ b'^ * ^° '" n""**". until the emereene,'
practicalfy identreaf a faS Jt^^iTZi^JuT'"''^^'^'}?'^^'''^ ^^'^Ven.
of the temperature conditToLt thelprin^fnK^ f^.^V'"""'*-^
mean air-temperature between the dates nfM«rnh o^ j \ •?'*' ^^^ averaw
of the adults Vmerged, was 49 d^«^ I-vL p Vu """^ "^P"' ^O- *hen most
was 49 7 den-ees Fkhr Tk! .. ^^ *"'• •f"'" **>* ««">« Per'"d in 1917 it
coveringVh^'^^'Sme wlre*^ r^Siveinsl'd^Sr^^H^^ ^ }«'« -' '»'^
Fahr. It is likely that the e^J^ZlLiafJTu^' ^"^J^f^ « 5 degree,
kept, would have proved to have [w. ZJ ' •?'ll" "° '**''"'*•' ^Kures wen-
owing to the two deSL hi«h?r vip« """^ *-^''" ^^'^ ^^^ <"^ '«>■ »917
abnormally highTaiSKd sno^dl ZlL"?hr «}''-»«™P?^«t"re- Only. th.
might have offset the teSrS «Hvfn?f„ k "'^ '?°"*'>'' "' **»«' y^«r »9><i
influence on the activitir„Tthe e'L/^ tl^ins^ 7tSlA ^^'•'«i-» '-Hardin,
climatic factor, such as low temt^nftiirA nr „K^' ",™'?^* }^ "ti»^ that anv
the emergence of the adIiZ f3th^'"^ll"UuCi ?h."'^"' ''^''!' *'"• ^"'"^
the damage to the trees. Unfortunate!^ suThRSw K '"^"n*,?^ "taving off
influence on the time of bloss^^ng S^ihat the S? „i.'" **'"^™"y, \''^*^
depending largely on the same sPt ^ u^ the first appearance of the thrips.
most yeafs wifh tVCpinLg'oT^thfsutStdy*'"''^^ '^"' ^'-"'^ "'
the iTn'dl^ililroTLVTh'l^l^^^^^^^^ -•--. 'n the.air, i..
rinl:tr\trn\\:^fi^^^^^^^^^^^
are al«. arranged in paralfel SS fS'tKke'^or^o'Cal^^^^^^ " '"^^ ''''''
""''oU^-Or^'rlJir.r^^^!'^^^^^^^ THE EMKK
ISLAND. MAR. 27 TO APRliTisi. I«7 AVD HFrORn/^^^ VANCOUVKH
FALL BE-nVEEN JANUARY AND APRIL S ^d ."."^.^ ""^ RAINFALL AND .SNf)U
M^«II "•."?'■"""" .«'f ♦••mpeniture, M»r. 27-.\pril 30
Mean minimum air temperature
Average mean air temperature
■«n maximum noil temperature
minimum soil temperature
le mean soil temperature
Mean maximum temperature on gram
-Mean minimum temperature on srasa
Average mean temperature on gran
Total rainfall in ineheg for January
1 Ota Bnowfal! in inches for January
Total rainfall in iwhes for FcbruaAr
I Ota snowfall in inches for February
Iota rainfall in inches for March
Tota snowfall in inches for March
I otal rainfall in inches for April
Total snowfall in inches for April
SI
HABITS.
Food Plants— Native and Cultivated.
In addition to being a pj^t of dociduous fruit trees., the pear thripn ha*«
iK'tome thoroughK e«tahli8he«l on many other trees and Hhrubs on \ancouvcr
island, chief amou|? which are the broad-leavetl maple (Acer macrophyllum)
June berry (Amelanchier florida), willow iSalix Hcouleriana), red-flowerinff
<urrant (ffj6f# gartfutnrum). choke cherry (Prunun demiom), XuttailV cherry
t\uUaUm ceraHtformtn), and also, incidentally, on skunk cal)l)ag.. (LyHichiton
himMhatkeme), Douglas fir (P»eud(Amga mucronala), (Jregon RraiM' (Herherh
..(■rrtwa), daisy {BMt» perennh), and dandelion (Taraxacum officinale) In a
nursery, it was found to occur on certain ornamental shrubs anti trws such as
Andromeda floribunda. Viburnum opulenta, as well as the Japanese flowerinir
|)lum. "
I'
1917
60 I
.TO -I
4» :
47 ^
4.^.'
46 •
44
IT
I
<l
4
flu. 13.— Shiiwing a cli'Mtn>yr(l bli)n«)iii-bu(l and an injurnl
l)li»woin-clu.ft<T ofthi'liniail-lfavcMliiiapl.-. Am mnrrophyllum .
Mays, 1917. Injury iiiu.>«"cl by thr (cfMiinn activities of tin-
adult ppar thrip.-<. (OriKinal).
* pit has been fully demonstrated that the species can succes.sfully complete
its life-history on the broad-leaved maple, the June berry, choke cherry, and
Xuttall's cherry, causing damaRc ex.-utly , .'rallel to that "which it commits on
deciduous fruit trees. There is no evui. ; > , however, of its breeding on the
others just enumerated. In 1917. ti e injury to maples was greater than that
caused to any kind of deciduous fruit (rr •>. and was widely distribute<l through-
out the Saanich peninsula and southei.i ections of the island, extending also to
the maples of the neighbouring gulf islands. In one marked ca.se, twenty buds
of a maple examined at Duncan. V. I., yielded almost one thou.sand thrips. The
liuds were seriously retarded in their growth, and many never recovered from
the initial check. Late in the summer, when they should have been in full leaf,
the trees presented a miserable, bare appearance. The maples .skirting the
ti
V
r
32
t!!fSp1^of5!rr;t^^^^^^^ Figure 13 represents
ff lied to develop, and the blo^sZ-ohf^fpr in P P^°}l«'^P^' «« shown, one bud
-should have be^n long and feaZerv more 1'" -' "* '*'''''* ""^ contracted
leaves at that time of X FiS T4 In S. P""^'?" • *? *^« «'^« «f the
petioles being badly blistered dndTarrtl h .1^'^°*^. '"J^'y *« maples, the
the hatching of the larv« " ^ ^^ ^^^ oviposition of the adults and
11
b
%
31 , 1917. (6tQm\) ^^ '^' *'•"'» '"'^« hatched. May
lay
When ^ne'cSnSr^'ThJ^ilde'S.Ilit;^ ^'f T;''''"^ -'' '^'-''^ ^'--
i^laml, and their r61e as Kmlinf re™ IfJu /'"'" f-'.^*''^ °» ^ »nc«"vi :
eradieative measures in reSo the Do^rihr^^^^^^ be readily understood th...
whether its establishment*^ on na ive'^food Snt'"''' ""V"^ the question. As ,
theory of the indigen.)usoriKiLf?KeirthJn- '"" ^"^ ?'"^ *« «»PI>«rt H:
fieant that the insect hc^ K fo^mH '^ S'" TA" *" ''"^^^
orchard. Likewi.se, w.^ found o be ZrT^^"" ^^ "''"^ ^'^f^"* f--"'" ^"'
the gulf islands, both inlani and a L^re s^Xor^ofr '\ """''^^ '"'^'''^'^ '
fruit trees, and sometimes senari nH fr!.L k .' ", '" ^'*'^'"^' "lere were 11.
timbers. separated from orchards by thick shrub and tOl
33
Susceptibility or Fruit Trees to Attack and Injury by Adults and
Larv,b.
So far as one can judge the relative susceptibility of the different cultivated
fruit trees to the effects of the thrips depredations, the palm must be granted
to pears among the pome fruits and to prunes and plums among the drupaceous
varieties. On the whole, it is probable that the latter, bv reason of their smaller
and mo..- >nder buds, ultimately suffer greater damage than the species and
var- <:<•> ,.; rhe .?r;ngeneric Pyrus. It might be well to set forth in detail the
var (Lis species ol <;ul ivated trees attacked.
TABLK VIII -CULTIVATED FOOD-PLANTS OF THE PEAR THRIPS.
Family.
Rosacrs.
.luKlanilapite.
Genus.
PyrtM. .
Cydonia
Prunm.
Juglan^
Species .
Common
Namea.
communis L
maluH L
rut^jaria Pers
(irtum L, vara. ...
domi'Htica L, varn. ,
dumeMtica L, vars.
innililia L. vara. .
amygdiilim Hook
(irmeninca L
Perxiea Benth
regia L
Pear. . . .
Apple
Quince. .
CheiT>'
Plum...
Prune
Damson .
Almond.
.\prieot . .
Peach . .
Walnut...
Nature of
Fruit.
Pome.
((
*t
Drupe.
(I
Form of drupe
Some of these species are not grown on a commercial scale on Vancouver
island, and for this reason the damson, almond, apricot, peach and walnut may
be eliminated from our considerations.
They are, nevertheless, with the exception of the walnut, recorded among
the principal food-plants of the pear thrips in California'. Should the pear thrips
by any chance be found in the future to assume economic importance on the
mainland of British Columbia, the apricot and peach, at least, which are quite
extensively grown there, will probably suffer seriously from its attacks.
jr
. 1
DAMAGE TO PEARS.
The damaged buds of pears are the first to arrest attention in the spring,
(ng. 15, A). Working their way in between the opening scales, the adults begin
to feed on the tender parts within. As a consequence, the buds begin to "bleed,"
exuding a sugary sap which crystallizes by evaporation on the exterior of the
bud, imparting to it a dull glistening appearance. Where a number of indi-
viduals are working on the same bud, it fails to swell and assumes a shrivelled,
' scorched " appearance, characteristic of intense infestation. Whole trees may
be thus affected. In time the injured buds are attacked by the spores of blue
moulds which cause them to turn a bluish-black colour. Some buds will contrive
t() expand and send forth weakened blossoms in spite of apparent serious injury.
The ingress of the mould .sp,ii,« i,,, however, an effectual check to further
development. Toll is levied on all the tender parts within the bud, leaves and
their petioles, blossom stems, the developing ovaries, and stamens with their
anthers.
I
34
ii.
m
I'll
Hi
Si
35
Thf fiama^p throughout a poar orchard is not always bv any means uni-
form. It IS ofton diffirult to tcndf-r a satisfartorv explanation why, of two
trees of the same variety situated side by side, one "will have praetically all its
bud« rumed whilst the other will set a fair amount of fruit. The same phenom-
enon ha.^ &lm Ix-en observed in the case of two adjacent rows of trees of the
.same vanety. In the orchard at Royal Oak, an isolated pear tree of the
>heIdon vanety surrounded by Hart let t and Rivers' Princess pear^ was so
extensively damaged m the bud stage that, throughout the season oi 1916 it
contra.sted quite strongly with its less stricken neighbours. The only reason
which can be a-ssjgned for its poor showing is that it develops slightlv earlier
than the other varieties, and the adults had committed irreparable damage to
the buds before attention was called to its condition and a treatment applied
More significant even than this ca.se was that of a Duchess of Angouleme pear
grafted upon the variety Rivers' Princess. The graft is a .somewhat earlier
hudding variety than the stock, and the time of .swelling of its buds coincided
approximately with the maximum emergence of the adults from the soil. It
thus laid Itself peculiarly open to attack when the closed buds of the stock were
as yet tightly closed and protected from injury. In one tree the graft, constituting
about one-fourth of thf foliage, had its buds almost completely destroyed in
•ided contrast to those of the stock which had made comparatively good
)wth. One IS thus forced to conclude that, .so far as the pear thrips is con-
decid
grow
ceme<l. it is unwise to graft an early budding variety on (.ne'which develops
Its buds later in the - r-.._.,L ... .. . . >
insecticide will not on
pest on both variitics.
infested bv adults; but
season. Further, one and the .same application of an
this account prove equally efficient in controlling the
Pears of the Bartlett and Bosc were (piite heavily
the timely application of sprav solutions reduced the
early injury to a minimum. Louise Bonne, F'lemish Beauty, and Rivers'
Princess, by reason of their later ilevelopment, did not suffer "materially It
must be remembered that the number of adults in a bud is not always a reliable
iTiterion ot the damage that is likely to accrue. Ten or twenty adults attacking
a young opening bud will often do more to check its future development com-
• v than fifty of the >pecies working in a i)ud which has made greater
and JMconie strengthened by reason of its growth,
rnea.-ures should be vigorously carried out; tor the more
that will persist to lay eggs.
grci
Nevertheless,
, , , inexorable the
ti ....nt. the f.wer the a<lult> that will persist to lav eggs, harbingers of
ilamage to come. Nor must a truce be called because' the miinbers of the
adults may be dimi:.i-hing. Xo matter how carefully the trees of an orchard
may be sprayed. th< r.- will always be a goodly iiuiiiber of adults which will
escape nemesis. Therefore, one must be pre|)ared to make an additional treat-
ment against th<' larva' which hatch from the eggs laid by these adults. In
this way a crop which may at first appear to be a coniph'te failure, may finally
yield a respectable return and amply repay the owner for the labour expended.
With an insect so insidious as the pe.ir tlirijis there <'an be no relaxaticm of (me's
efforts. Half-hearted measures an> likely to prove more expensive than none at all.
-A.- to the l>est time for applying insecticides, no hard and fu.st rules can be
drawn up. Seasonal differences may cause an early or late appearance of the
thrips, according as the conditions are favourable or otherwise. Under the
circumstances, the orchardist must rely to a great extent on his own judgment
and decide for himself. There can be no doul)t, however, that once the thrips
has reached the buds, control measures catm"t be undertaken too .soon.
nA.M.*(iE TO .API'LKS.
On the whole, apples do not seem to l)e so susceptible to injury as pears.
The buds are more robust an<l appi ar to be less affected by tlie activities of
the adult.s. Generally speaking, the three varieties, King, Ribston pippin, and
Baldwin, seemetl to prove more attractive than Duchess, Red Cheek pippin
■
1?
I
I
'■ ■:
^1
'I
1
w
■:r
36
the expense of making a treatment Tr ♦ h '"i'^ff'^tion so heavy as to warrant
instituted aKainrt the la^vL after^h/h. adults although operations were
feeding-ground 5 the W ,m apph' ftheZr^:}'l''*""t '^r"^' P-^ ^"^^"""^^
As many as twenty to thirty maTe'^ouL^lXtTo^^f ^^^^^^^^^ S^fy
s's£J:^l&^rx?srtri •»'*":" «'-j«- After this h,.
and causing the LSamJ ^^ ^^^^ \*'''"'''-'' ^'''■'t"'K » further flow of su,.
attacked,rand boc, n g Wn th, v w it r^^^^^^ ""T r^*''' ^f^^ens are aisl.
the larvffi are rc.«nonsil.l,> f^r Ii^' " >•! ** "* '*"'• Feedmg on the young fruit
also quite oommrcm isitVZrs'"^" '^'.''I'r, ''"P"''^'-'^ known as 'IJIb '•
trees „n whioh adult ^ S'C.rf, ■ ^^ 7"^''* '''" ^''P'^''^''''' t^ose untreat..!
Krcutest larval injury ttluhliXv" I '"■'•' "TT""''' ^''" "''Perience th.-
fruit to the loaves, where thev m vT.o ?» "IT'T "^ !''e™Pa«s from the youn^
Pr.ncipal veins. The lo"utLe'';L':^J;:!n"1.X"p'i.rtt;d ^'" '""^"" -^"^^ *' ^
pediee"sli7]6).^'''^*''*'""'' """'"'»"« ^'KK-^-ars will he foun.l on the young fruit
37
DAMAGE TO PRUNES.
The destruction of a prune crop ))>- the pear thrips proceeds with great
rapidity after its inception, and, taking tree by tree, the damage is as great as if
not greater than that caused to pears. For ten years there has not been suffi-
cient return from either the prune or plum crop in Vancouver Island to repav
the labour of cultivation. As soon as the adults emerge frop- the soil, thev may
be seen on the outside of the buds impatient in their efforts to effect an entrance
Once msxle, they soon make their presence felt by destroving the most tender
parts. As the bud .scales arc forced apart, the young leaves and blossoms
instead of being fresh an<l green, appear brow-n and decaved. The slightest
touch will cause these destroyed buds tu fall to the ground' One is often sur-
prised by the large number of thrips which are found feeding on the blossom-
stems, the tips of the petals, apH on the .stigma and stjle of the blossoms before
Fill. 17.— Olivit cticro' infrslcd by liirva> of pcir thrios
-Muy 31, 1917. {Orminal).
;iti(l at't.T they have opened. Year after vear the iirospects for a licavv croi)
imiy appear bright and rosy, only to be reFX'atediv blasted l.v the dejjredations
"t the pest. It is our conviction that the spray .soimions appliful at Hoyal Oak
this year would have accomplished much towards saving the croi) of" Italian
prunes, but unfortunately the occurrence of two sharj) attacks of frost on May
" iind 12 blighted our expectations and entirely negatived the r»"sults. Plums
of the Pond's Seedling and Columbia varieties were not so heavily infested as
the Italian prunes. It is rather a disheartening si)ectacle to enter an orchard
and see the prune trees presenting a scorched appearance, with an isolated
blossom here and there reminding one of the departed glorv of the crop. In
l)runcs and plums the scabbing of the fruit caused by the feeding activities of
the larvae may seriously depreciate its market value, if it does not indeed render
It quite unsaleable. Were persuasion necessary, nothing couhl be more stimu-
lating to an energetic campaign of combating the thrips than this story of
prune destruction in the Saanich peninsula. As has been previouslv mentioned,
the deposition of eggs in the fruit petioles and their con-sequent weakening may
also account ,or quite heavy losses in prunes and plums.
DAMAGE TO CHEKKIES.
Although cherries are severely attacked by adults, they generally set
quite a heavy crop of fruit by reason of their comparatively large product-
iveness. The thrips first begin to appear in numbers as the buds open up
; -
if
i ■
<■
II
if
i
ft
;■ f
tity
i'
*? ^
II
r.:'
38
or to .„„,.. oxtont. ,1... .^ •«• rs norfcwH '':""« ""i'"^ l>u.l-rl„Mtor.s ;
Oiik in ,1,,. spring of Um it was our rivil .«* * i "'"^ "^ '^''P- ^^ «">"!
Ih' th.« thrips ,lania». t(. -h.^HL J •'^ to ohwrvo how intrnsiv.- iniRhi
.ypross-lik,. appoaran,-,.. In .!» ni« s .^.ir " ""r* ^"'•'""' '""'
;;. pusl. out thoir l.losso„.s anVl^v/Zu^r iaS;v'"''lKT.r.'";' T*"""'
had luvn s.-cniinRly arrested owinir nri'snm ^^1. . \i "."^ .'" '••'Vflopmcnl
The elus,,.rs ha.l first l.r.m-^e land then h S.. ". 'rr''^'*"'" "^ ""' '"'"'«■-
to the hranehes durinij the winter ,1 M«rfi l'"''.'- , "^'"'J' ■'•'niained attaehe.l
irrxt-daSiS^^
«. .. .itth. e. • e ror not^^^tll ^Z t^^Xrll'lSS/-^^^^^^^^
the iff^^iiiiuiS:: ~;Jn;;il;;;xi::;rK.i""'^ ^f^y v -'""--
mumnv a similar eon.lition s?nL from the rnni "." ','"■ ''"* •'"'• """' '"'«'"
iunouKst the foliage. Ti.is se.Sarv ^Hm„i. '^''P™*.'''' «'<•'' very of small sh,,,
for a de,i,i,..l redu,-ti,,n f the Is^^^^^^^^ ' V""*'' T'r^'"'^' '""' r.-sponsil.]..
1>.' rather detrin.ental to tlu. gro~te "^ "'" ''"'^'"''- ^^'"''' "'"^'
i
inst^riVin'TonSVIr'Si:: "'">• -'"- ^o ^he young fruit was ele.h
Olivt <herrv-,r..(. was teLll! • > ""•'".'Vf'- i.slund. (hi Mav 31 1<)1
"^ •"" "-":..Ts of larv. thiu'r ;i.'L.ii;^^i;ja;r:;;e;rr • '•'
REPRODUCTION.
OviPOSITION.
arises];;^fc!;SJ«^;,iSt;;'a,i:}o„Sf ^^T '^J'r^^ eharacteristi... ,
for its reception by ,iri?Z?at "„ of ^h '"'T" ' •?'^."'^^ '" « K'-""^"^ -I'lrP'
segments. Four distinct StoTSer^ilf' u?*/'*' ^^^'T-*«« "^ Jhe two ultin, ,
pair originating from the eighth and the ..nn "P^T'^!""' ^^'^ '"^" «"''"
abdominal segment, ('urvfng Wry ^JntuP'^rr.'""^"."": P'^"'" ^'•°"' ^^'' >'i^
on the uprn-r mIk*- of the ower plates, the apparatus is rendered more tensile
«h.le at the same time allowing of a certain degree of sliding pfavTthe uppe;
plates on the lower. Lxeept when actually in use, the oviJosUor L hffn
,1. Its receptacle, a ventral excavation of the two last segments.
lorminal. abdominal sei{mpnt!.,rf adult to show
the ovipositor. X l.W. (f)ri«inBl).
The actual time taken by the female in laying an egg varies from two to
three minutes Sometimes the ex.serted ovipJsitor is ensheathed too leen v
,n the plant tissue,_and the in.sect experiences much diffi.-nltv n IV^S^
.. the plant tissue,_and the in.sect experiences much difficulty in extricating
Fir. 20.— Transversp swtion in outline of fruit-stom of Italian prune to
show CKR-i'haiiiher!! in the outer laver of rell,« feorlex)
Drawn from actual Hpn-imen. e. epiderm: c. rortex- rr
ehlorophyll layer of rortei; e. h. hair; p. r. egg-f'hamber.'
f. r. />, fibriVVRseular Ijumllra; m. pith. Xlti. Ulriginal;.
It. On one occasion an individual oh.served ovipositing in the stipulate leaf
''t a King apple, was engage-: for about thirty minutes in trving to withdraw
Its ovipositor before success atteniled its efforts. Numerous cases were recorded
'-t the ovipositor being so .securely embedded that the insect was effectivelv
held prisoner and finally succumbed. "
I-
•
f
;!•
- t
: ;
i
,
i'l
^0
m
lu
at H«ht angle, to th^e 'H^V-'Arp^ A^Xre^t^^^^^^^^^^^^
I!
''''Y*!'^*'"'" '"J^^Ml'aeieL^.-j..-
' in Si,J'mof'„Vpl.-.'^vi^if^ •^•^-'l '•? "'- "'t -f ovipositing
f i>auo. X 126, (OriirinLn; ""hMl'IfHl and r..prr8 Mt...! as evi.i<.nt in tl... pl,,nV
it.s mouth vlHsVm.rTh "T"^ '•'•■" *" ''"•^'••' »ho .'pi.lerm first wr
!ii<
41
very rarely einbe<lded so deeply as to come into .-onta.t uith the fibro-vaseular
bund es of blo88oin stems, leaf-pet iol.-s, and veins, as the ease may Iw (figs.
20 21). Dessiccationis fatal to the e^g, hut so iong as growth eontinues it
cells amount of moisture m its char.lx-r among the parenchyr-i^tous
Figure 22 shows the insect in the act of ovipositing on an apple fruit-stem.
At the point where the ovipositor is eml)ed(led the ..tern is represented a.s .semi-
transparent, the better to demonstrate the position of the egg-laving organ
Pa I
HENOC1ENESI.S
ho far as is known, no specimen of the male of this species has vet lieen
recorde<l on the American continent. Diligent search for males during the
course of our investigations m British Columbia have so far been unrewarded
Similarly, according to the very e.xtensive observations of Moulton" and Foster
and Jones' in California, nothing but the female was ever taken. Onlv one
in th'■^'l^f^ ^^. i''*"". "'^""Vi.''''' **'"• ♦'"'* ■" f^"K''"«' from Plun> I'lossoms,
in the district of Lve.sham Worcestershire. The spe.imen was collected bv
u ■ 1.5 ^'T' f".':'"'''"'>' 'i th*- ("o-Pcr Kesearch Laboratory, Berkhamstea.i.
Bagnall' to whom it was submitted, briefly described it jis being much smaller
than the female, with wings consi.l.Tably over-reaching the tij) of the abdomen.
Such a description is evidently rather inadequate.
In the absence of males, the normal method of reproduction is partheno-
Kenetic but there is no altcrnution of generations such as prevails among the
Aphididap, the gall-formmg Cynipiche, and some Tenthre<linida>. Tiie signi-
hcance of the phenomenon is that it secures for the species prolific multii)lication
Inhke the parthenogenetic species of Phasmi;la> ami Aphi<lida«, the pear thrios
produces but a single generation per annum.
I ' 5
\%
CONTROL OF THE PEAR THRIPS.
sulphate iiave proved effective
however, to ensure satisfactory results rest.<
application of the insecticide.
As a result of two seasons' activities, Htiti and 1917, to determine t he
ettectivene.ss ot suitable control measures against the pear thrijjs, it mav be
chinned with every degn'." of assurance that the insect can be satisfactorilv
kept in check. •'
Spraying is the only suitable and satisfactorv method cf reducing the
niu-l.crs of adults and larvte; hence, most consideration will be given to this
piui>c ,,i the subject in the pages that follow.
Spray mixtures consisting of miscible oil No. 2, or whale-oil soap and nicotine
as controlling agencies. The jjrovision necessary,
to a gr(at extent on the timely
, . , Therefore, in regard to this insect, and probably
inore .so than with many other important orchard i)csts, it is advisable that the
growers should make them.selves well accpiainted with the form and habits of the
thrips so as to decide for themselves the correct time for spraving. It is unsatis-
factory to state in other than general terms the approxiniati' dates for applying
the spray, inasmuch as no two seasons are ab.solutely similar in respect to
climatic conditions. Further, it would appear that there mav be from year to
year a decided variation in the degree of infestation affecting' the same variety
of tree. In view of these facts, it will be readily observed that a great deal
depends upon the carefulness and skill of individual growers, and it cannot be
too frequently emphasized that the essential features of the life-history of this
insect must be clearly understood before control measures can be intelligently
undertaken.
I f
i i
H
II-
! I
4a
It w„ul,l only H,.rv.. to l.^sse„VK|^ 7thi" ImH IJin"" 1 " "'"""•V '"*"'" "'•*'''"•^•
iin|H.rtant |.„inf« «r.> pn-s,.,,t''.l. '"••Iu'I'hJ here. Thcrrfcr.., „nly the moHt
SPRAY MIXTUREH.
the W lS"Sh:r":;S'i';^Kj;n'\^ treatment was n,a.le against
first revoale,!. In l«l« a tot^l « 1 vj.frni .r '^"TTX "^ *•>:' ""•^'- '''"P^ *««
over an area <,f 138 aeres, «i^ iav: hv flrn! "^ ''''^T?' ''?''''• '''"tHI.ute,!
1917, a similar .ampaiim of «nr«Lv"L ul, •'^*" *".•' '"*"'' nmehin..«. hi
Moeks of trees were'St." K't ^e^ffi'irj"'/*"- • '" '•"''' ■"••*«""« '<""'»
mixtures an.l the numln-r of Irav Inii-^^ ' ''""""'' "*"'"«» hs «f sprav-
results. ()„r work. thn.uUout w,L?rS^^^^^ neeessary to ensure the In-st
obtained against the peTZCTJhfn^^l ■ f."'' ^'"i"** ''^ '»>- ''•'•""'♦«
The inse,.tiei,les ehiefly emploml duri^" thpri" ''"'* ^"^ ^"^'^ «t«t-'-
mixtures .-ontaininR either whaler,! "nan or mf • /'^"■■'T""'* consisted of
t.on with nieotineM.lphateand^;:trTs'l?[i,„^;;^^^^^^ "'' ^-- 2 in eombina-
MisriBLE Oil No. 2.
insecScJ:' •!i;;t:ir'Z:T2ic:;J,;''iirtf*«»'- »»>.. use of miselhh. oil in
province. It was un.Ierstoo , h Ve J^v^ " '*™""*5. ^^'' ^""tRrowers of this
of the pear thrips in ("Sn a an/K S^^^^
\ ork state. Information wius rt^eived from S'^'^i- f*^""™''''" ^P""*" '" ^^'^•
cultural Experiment Station, CorvallTs oZ"' fhn! I""' ^"™'''"'y "^ ^^'^ Agri-
dcRr. '» offset the value of later sprasannlilJ.f'''' ""^lu^'" ^PP^'^'"'^ i" «ome
'nrhc, ..S-, a fungous disea.se affect.nriunn whi.h ""• ""^^™''"«?^' ^"^eofabraea
the ru..>t serious in the northwest coital i^nH r '« universally regarded as
datec .Mav 10 iQis he Vlrni/f** t- '^^V""*' of the Pac fie. ]„ a letter
wcvuld say that we'ha'; rt^lCe^"; sSt ' V.^'^'r ^ " ^'^»> ^'^'^'^ '- «*' I
following the oil spravs, appSo s f iLf T u ''•'"' °„'""K *" ^^^ f"''* th^t,
the trees in the fall for' anXacnose' wiH VZ " ?^"' °' Bordeaux delivered on
one may have a complicatiTwhLr Sr?ot'?V'''''-^J!^ ^«' ^'''^ '•'''^»"
measure..' Furthermore, we arHnd j'ted to 4 W *" p '^.'^*' ^/"^^^^^
Chemical Company, of San Francisco Can^ i i* '^ ^°1*? °' ^^"^ ^^-n^ral
drawing our attention to the possHjUitv nf f h/ "•"'" ^«t«'/pril 30, 1915, for
following the application ofmSfe S L 2 To'n.?T t^^^^^^l^" '"Jury
care is requ red in the use of oil «,.L, . '^° 1"*^**^ '"'^ words: " More
pear tree.:* The folfage Is te TX Z^E^" 'T f'' •''«°™'"« *'^«« "'
-njury. Varieties differ somewhat fn this rejLdZ.t In ^' ""f," ^"^'^^PtiWe to
ible than pears and prunes." Dr E P Fett" ji i*^" "'^ "^^''^ '""'•«' «»««^''Pt-
2. Is effects on various kinds of fruit trees ^
With tSrv^JnWSelEc^t^ ""'• »-d-- •»-»"-.
their composition varying accordTngt? the tr^'V" "^™'«Si'>^«• oil were tested,
administered at the time when the1,uds were ^fr°/ ''PP'^'^^.V""- For the fiis,.
toevery 200 gallons of the mixture.* »>ursting, 5 gallons of oil were used
l!
43
For the second and third applications the quantity of oil was reduced to 3
and 2 gallons respectively. In come cases, four treattti. 's were made, and
the amount of oil used for the fourth was two gallons a^i in the third.
Several tests were made at different times before the period of blossoming
and after, and the results obtained may be briefly stated as follows.
It was found that miscible oil possessed great penetrative power and that
buds, even though partially closed, would gradually imbibe the oil beneath
their scales wil telling effect on the thrips feeding within. This characteristic
quality of oil is undoubtedly a great asset for a spraying compound to possess,
especially in the section where the work has been carried on, because the months
of March and April are usually attended by a slow development of bud growth.
As to the killing-power of miscible oil, there is no doubt whatever that death
is almost instantaneous for those thrips which are touched directly by particles
of the mixture.
It has been demonstrated that at a strength greater than 2 gallons to 200
of the mixture " burning " may result, «<necially to apples after the leaves
have commenced to appear. Injury of thi> natr to leaves and fruit was espe-
cially noticeable in the Duchess variety. It w;i- observetl that the hairs of the
leavts assumed a brow, appearance and shrivelled up. Their function, which
is lo regulate transpirativn, is thus interfered with. The epiderm, too, and the
underlying parenchyma are also affected. In none of the cases, however, under
observation, could the burning be termed severe, except in one instance where
the tree partially shed its leaves. \o specific reason could be advanced in expla-
nation of this occurrence, inasmuch as other trees of the same variety, sprayed
on the same day in another section with th' same mixture, were not apparently
affected at the time of treatment or on the days succeeding. Apart from a
temporary retardation in the gron-th of the more seriously affected trees no
permanent injury resulted. In the less severe cases the leaves seemed to revive
and resumed their normal healthy appearance.
Efforts were made to determine whether miscible oil caused injury to the
trees and their fruit not only in the same year as the app'ioation was made but
also in the year following. Apart from the set-back to certain trees in the few
days immediately following spraying, no sign of injury resulting from oil was
apparent either during the sea.son when it was applied or at any time in the
succeeding year. This was true in every case, whether the trees received one,
two, three or four applications of misciblr oil in the strengths before mentioned.
It is customary in the autumn of each year to recommend orchardists on
the coast sections of British Columbia to apply Bordeaux mixture to combat
the effects of the apple tree aiithracuose, Xeofabraea malicorlicis. Applications
of Bordeaux mixture were accordingly made to certain trees to test whether or
not the earlier one of oil would interfere with its effectiveness. In the following
spring an examination of the trees thus treated was made with the result that
evidence was obtained that the oil did not in any way interfere with the efficiicy
of the Bordeaux. In the same way, it may be said with a greater degree of
confidence that the oil applications did not nullify the virtue of lime-sulphur
sprays in its control of apple scab.
Consequently, it is safe to assert that provided in the first application of
oil \ 'a the buds are breaking not more than 5 gallons to the 200 are used,
and the streni^ius are reduced to 3 and 2 gallons in the mixtures administered
when the blossoms are showing pink and after blos.soniiug respectively, no
damage «nll result.
Furtherm re, its killing-power against thrips is undeniable. Also, no
after-effects of an injurious nature to the tree itself nor interference with the
value of later sprays have been observed.
Whale-oil Soap.
Whale-oil soap has been used for many years in the orchards of British
Columbia and on Vancouver island in particular to combat various inect pests.
In our experiments we had in view the idea of testing: —
II
J
1
44
1. It« ..ffjMt in .ontrollinK thripn;
to 200 gallons .rf water iT^.^Sril^r*' ,"* *'"" "»*" "' '» PoundTof Hoap
»um ., r „f treatment. an.J t the ;rt«tT7.f i '"r•'^•'^ vari«l i„ nTjard to ih^
, It waM foun.l that whaleSi Jlln .v'l. ?i'*;"'''" "P"'''V* "' »''" <^«'
In many instances. o^p,-riMy^V^rT7- ^^t'^'^^y
t.viH. of l,ud, the deKree^c^f"*":;,'^';„;i" "i':'' " ''»'[ tree, whieh have « W
however, it ranks hut -■^'eoml n this L^^ ."''"w™'*'*"- ^n •"'•niparison with oTi
J-nce to the first appiieaf b „ "• -DTTn' 1 1 ^^ "'■^""'*"•»''''^.v »'«« this r efer-
fairly tightly ehilkl. I " Tater T« ? 'T" *^*' ''"'''' "^ "»"•>• varieties an-
opened and the leaves have Kn t7.w^^^^ made af„.r the K hav-e
of the two sprays are m.t so a^aTnt " '""' *'"' •'"^♦'"'"t wetting qualitiel
in the ma Sr; m' Xr;'th;"i;i"\"'- "^'T "' •'"• -P -- very rapi.l
o'l It was not quite .,, ,,ui?k7n H X n' TT ;''"•'">• »'it. As ronrpar™'
proved eminently satisfactory. '*' ''"* ^'"'" >" P'-««tiettl »tand,H,int it
Nicotine Sili-iiate.
JO.) »fXly»S3T,l\t„°S^^^^ <"■•"■;'■ ' ™.k-i..,
1 pint of nifotine sulphate to t he 9(mi „ li *"■ ■"*""'•• I" t»'e ,ase of the oM
amount of the soap Lxtur!^ ^"" '^""""'^ ^''■^ "-'- """« •* Pints to the . lam.:
|s merea.se,l very greatlv. In each eL^. '"7""" '"J!''""'* ♦'"''^ effeetivn, .' ^
■n-'^eot and finally .au.se. its "uffo, Lion * '^'\ "'•'" " fi'"' whieh surrounds t|,.
properties of the basic- const iuenLftW ^St^' "n "''^'r'"* "»*1 «P'-''«'l "^
LiME-Sl LPHIH.
tho ...ri^el^- 'ys!:5;"^EE^' ♦»><' rr"V'- ♦•• »- --tiai i,.
spring ,t seemed desirable to est *« '"'"'" ■''''P'*' *"' P'^ar seal, in tl
hnd whether or not it could be uTed as a^X'' T'""' ^^'^ '«'«'• t^rips, and .
Experiments, therefore, were carried cfu^Urthis If '" ''"^ "" "■• '^"^P ''Pra-
In every mstance it was ^h^Ji.„\\ \ ■} ""* **"" '» view,
penetrative 'qualities It was foun. t I' P"'''*"Tr^ """•• ^■•'"ing and inferior
when .t was delivered undeTcoSe Ll "e pr^sX an l"' ''"*'•"-"*"« '^'-'^"^^'
the spray. The results aga"nstlarv» ^"^'^ ^'"'" *^*' deleterious effect ,
f,^ P«P^«Prea.ling quaS^of ? . rmw[urrT/''''t<'/°'-y' ^^' here aga
stated m table X on page 49 it is onlvT '^•'t/afted from its value
'on IS slight, and where a spVlf "Svin^S^t'' ^"'" "'^^ ^'^^^^ the Tnfes,- -
the expense. ' "'*' sprajmg with o,| or soap would not warrair
been ap'plSt'^ertab ■tUrdsru'nVt"''! '™^-^"'^»'- »>- ^^r manv veu-
that the non-reduction of their number^ 'l" ■'^t^"'"l'>' '"^^^t^d ^y thrips^ u
sulphur to effect a suitable contlol '''"■'-' "'"^^^ *»•« •""'"'ity of liml '
^ Arsenate or Lead.
s^^T^'>''''^y^siiss;V:L,^''ih •"•'^"^ i »■' •■"
under rertain atmospheric condition, 7b. „ i ■ '. "»»"iered pciblc lit,.
S
i^Bi
4S
of the foiiagp. fjelipvf<l to l>e from this tau^. did wcur on one ot'casitm in our
experiinent8, but no (lermanent damage re:«ulted.
Provided the arsenate of lead is mixed in told wati-r and added directly
to the tank, and prf>vided that the strength din's not exceed 2 |>ounds or 2i
|Mjunda to the 40 gallons of the mixture, it is Ix-lieved to be quite safe to use
in combination with either miscible oil or whale-oil soup under the conditions
prevailing in the coa-^tal sections of British Columbia.
RESULTS OF SPR.WIXd.
NIethod of KEcoRDi.\(i Kesilts.
A count of the adult thrips present on the trees wji-s made immitliately
{(receding the application of the spraying mixture. The average number in
i>u(Ls and blossom.* or on leaves wa.s consideretl sufficient to indicate, as nearly
as (jne could judge, t':ie degree of infestation. Buds and blos.soms were dis-
-ccted by means of a sharp scal|)el and the number of thrips both inside and
outside. Wiis carefully recorded. After an interval of 1 to 24 hours had elapsed
following the application of the insecticide, a further count was made. A com-
parison of the figures thus obtained indicatetl to what extent the spraying
mixtu'e had l>een effective in controlling the pest. It will Im- readily under-
'* that in dealing with an actively motile organism this plan of recording
's has its defects, and the experimental error is likely to be ('(msiderable.
this reason it is not deemed advisable to present in extended series tabular
•videnct- of the percentage mortality of adults and hirvse. Suffice it to say
that the remarks on the preceding pages, under the headiriKs of the different
inse<'ticidcs, have lK>en ba.sed u|K)n the interpretation of actual ligures obtained
in the course of extensive experimentation. The force necessary for the
thorough application of the spraying mixture .sweeps large numbers of thrips
from the trees, and it is thus impossible to obtain comparative figures that are
absolutely reliable. Ii> . rder to determine what happens to those imlividuals
thus swept away. chee>f I >th sheets were spread InMieath the trees during the
progress of the spraying. On examination of the sheets it was shown that
the individuals which had fallen from the sprayed trees were undoubtedly
killnl. Thi> meth*Ml of rectifying the error of probability, however. — the best
that could be devised — was much too crude to provide results that could in
anv wi.». be considered exact.
With all due allowance for these difficulties, it can be safely a.s.serted that
the percentage mortality among adults caused by oil was 71 for each spraying,
ami for soap 68'i. With oil. the larvie suffered a i)ercentage mortality of
85-3 as compared to 84 with soap.
The V.\lve of Two asd Four Spkayinos Betohe Blossoming.
Some large Gravenstein apple trees were .selected for two treatments with
miscible oil— nicotine solution on April 3 and 28 respectively, and an equal
number of the same variety was sprayed four times, on March 29, April 3, 12,
and 28. After sufficient time had b'een allowed for the majority of the eggs
of the thrips to hatch, these trees were carefully examined in May. The results
expressed in terms of 100 calyces and leaves, are rendered as follows: —
TABLE VIII.-GRAVEXSTEIN .\PPLE TREES. SPRAYED TWICE AND FOUR TIMES
RESPECTIVELY WITH MISCIHLE OIL No. 2 IN CO.MBIN.VTION WITH
NICOTINE .SULPH.VTK.
Number
of Treatments.
AVIRAOE NCMBIR OF ThRIFS FIR 100
CAtrrlH AfTlR TRmATMENT.
-VvERAGi; Nl'HBER OF TuRIFS FIR 100
LlAVU AFTER TrEATHENT.
.\dult9.
Ijjrvje.
Adults.
LarviB.
0
2
4
16
4
10
341
ira
44
0
0
0
132
1
1
1"
I . j
If
i
f
i
1
-, {
II
• (
^i .
40
ThK V..CE OK EaBLV .so L.TK APPUC.TXONS.
Ihe results were recorded as follows >- ^ ^ ""'^ ^^''t'on 3 on April
AND 28: (2). ON APRIL 3;^. ON A^I* ^'^ °~ ^«^^ «
Section.
Treatment.
' Sprayed.
Control.
Average Number of
I-rve per 100 Calyce.
Alter Spraying.
Average Number of
I^rvje per 100 Leave.
After Spraying.
Percentage
Mortality.
Sprayed.
Control..
Sprayed.
Control.
7i-5
Hi
wit^^^'X^ *'''''^' contrary to what tiJif^u'^ Pestsand diseases in genertl
contrLioti "^ * l^^' number of Iwvte fn t h? ^•- ^"* *o»'d naturally
™P?«?i^^*'' therefore, to obviate thp^ha ^ "i"""* **>« reason of flight It i*
KiigiDie. ihe figures as given, howevpr -^ if *u "'" ''""''' •» consider.^
an
47
BuoDtNO Charactehistics of Trees.
The gradual growth and development of prunes, apples, and cherries,
from the swelling of the buds to the opening of the blossoms, varies considerably
in different varieties of fruit trees. The low temperatures which prevail in
the early days of the spring, tend to retard the development of the buds. This
fact more than any other interferes with the ready control of the thrips.
Emergence of adults from the soil takes place from towards the end of March
to the middle of April, at a time when the buds of the majority of fruit trees
are commencing to burst. The early spring is often accompanied by cold
winds and rains. The adults, therefore, which have emerged, are forced to
penetrate beneath the imbricated scales of the buds for protection and warmth.
Feeding takes place within the bud, and the adults seem disinclined to move
very far. When a bright warm day is encountered, the thrips at once assume
great activity. However, it has been observed in the respective spring
seasons of 1916 and 1917 that a great deal of damage takes place during these
cold backward days after the first development of the buds has commenced.
The whole crop might be entirely ruined in three or four days of such weather,
and this is especially liable to happen with pears. Consequently, it is essential
that growers should fully realize this danger and prepare themselves accord-
ingly. They must be careful to note the first appearance of the adults in the
spring, and must differentiate between early and late varieties of trees. As
has abeady been remarked, the early bursting buds are most liable to attack
in the spring and they should therefore receive the first attention. As a
guide to orchardists of Vancouver island, the facts regarding the develop-
mental phases of different varieties of fruit trees have been tabulated as follows: —
TABLE IX.— BUD AND BLOSSOM DEVELOPMENT OF FRUIT TREES IN THE
SAANICH PENINSULA. VANCOUVER ISLAND, B.C., IN 1918.
Crop and Variety.
Dati.
Buds Bunting.
Buds well Open.
Trees in full
Bloom.
P'nn—
Kieffer
Bartlett
Flemish Beauty
Bosc
Louise Bonne
Boussock
Jules Gnyot
Rivers' Prinoess
Applet —
Red Astracban
Duchess
Gravenstein
King
Re<r Cheek pippin
Belle de Boskoop
Delicious
Crimes Golden
Wealthy
Ben Davis
Rome Beauty
Northern Spy
Plumt and Prunm—
Italian Prunes
Columbia
Ponds' Seedling
Damson
Chtrrin—
Olivet
Bing
Royal Anne
Mi.r. 26
" 27
" 27
« 27
" 29
" 29
" 29
" 29
Mar. 27
" 28
" 28
" 28
" 29
" 29
April 1
" 1
" 3
" 5
" 5
" 5
April 10
" 12
" 13
" 13
April S
" S
" 5
April 1
" 1
" 2
" 3
" 1
" 1
" 1
« 2
April 5
" 2
" 6
" 3
" S
" 5
" 9
" 9
" S
" 8
" 10
" JO
April U
" IS
" 18
" 18
AprU 10
" 10
" 10
May 3
•' 4
4
" 4
" 4
" 4
" 6
" e
May 14
" 4
" 10
" It
" IS
" 18
" 20
" 18
" 19
" 18
" 20
« 22
April 24
May 1
" 9
^"J \
m
•■
WHEN AxND HOW TO APPLY THE SPRAY.
Climatic Factors,
the orchard, aid bud devSpment conditions, state of cultivation of
cool,?u!l.^,Syt^t£ tllT^Siefi^tet^^Vr V^""-^''^^- '"
came, or they burrjw bcnwith thL r>^*^- *°*"*'^ "' '"« 8<m1 from whence thev
should choo^, if T^SiWe,TwamTrSt st^*'? °' *.^.* ''"f ^^^ ^'•'^'"dist
shown signs of dLvclopSg in o™er tf rnX't hi Tl''*' '^*".**'« ''"^^ ^ave
when the adults are in evident L the b,H« %!,"*. ^Pfi'*'**'""' »* « «»«
dull and cloudy for a considerable wri^ bStlth i'?"^'* *''*. ''*"'*''^'' '«"»«'"
Fahr. or above, he should wtisfv hf:^^i* k ^*? * temperature of 50 degrees
as to the activities of the ad^t?"^ wSf it Jan ^Zn'J^^Tf ^ -^^ '^'^''^^
already entered the buds and kre Iwi^W^h^ .^ "^ *^''* ^''.^ '"«««*« ^^ave
operations should commencri^wouTd be courtiLnT^; '?"«!'''»« «P"ying
action in anticipation of bright wrther-^^^*-^^'" 1° ^^^^P^^^ *ai
all likelihood be irreparable^ thTtime. "^"'^ *° *''" ^"^« ''^"'d in
Cultivation.
is disTl!rbKnd%tr?fofeTitpti^i,^^^^ °' ^''^ ^-* *»»«* *»>« -i'
of the thrips in ploughed Sards 7h^n ^i'n fh ""'"^\*°/""*' emergence
unploughed The theoiv that Dlmi^hini^ T ^^T °'"«''>ards which are left
i«not.a?all.ound,b?c2SotcTntf ^"rXte "'/'^^ T'''
requisite to destroy the cells in which ihnZ Ko,"f the fineness of condition
the adulto are m^relv waitini^ for Tha rT, ^ i "^ " ^^'^ ^^^ ^^ter. Further
and the readier^nXS^^f lVa\mT&tr Int'S^^ °t^ ^^^ ''P":
requirement. It may be that the marJ^ll^iA Ploughed soil supplies thi^<
disturbed soil is of indiV^t advantwe tofh'^'l^T^T'l"? °1 *•"« •°«««'*« '''on.
reaches a climax muchTore ST and o»ri"**f '" .^''** ^'^^ '^^^^^
quickly where the necessarT^recSns are taken H^^" ^ '?!!*"'"^'^ "«^"
.« careful examination comLU S "aSt? of actbn ' "*''''"' *••' ^''*''»>*»^''
Schedule or Applicat'ons.
dra^"up*ttlLw?rthTsJra?^^^^^^^^ tPP«-«ons has ben,
Vancouver island.— sP™y>ng of orchards of the Saanich peninsula of
49
TABLE X.— SPRAYING CALENDAR FOR THE GUIDANCE OF ORCHARDISTS
COMBATING THE FEAR THBIP8 ON VANCOUVER ISLAND.
Number and Times to Spny .
Mixture for
Severe Infestation.
Mixture tor
Light Infestation.
I«( SprttK adult thripi in numbers on or
in the blossom buds, buds burstins,
about April 3-fl.
Miscible oU No. 2. S gals,
nicotine^ulphate, 1 pt.
Water, 200 sals.
Whaleoil soap. 10 lbs.
nicotine-sulphate, 1) pts.
Water, 200 gals.
Miscible oil,°5 gals,
nicotine-sulphate, 1 pt.
Water, 200 gals.
tnd SpnK adult thrips in numbers on
the trees about a week before blos-
soms appear, about April 2»-Hay 1.
Whal^oil soap, 10 lbs.
nieotineHnilphate, li pts.
Arsenate of lewl, 8 lbs.
Water, 200 gals.
Miscible^oU No. 2, 2 gals.
nicotiiie.«ulphate, 1 pt.
.Arsenate of lead, 8 lbs.
Water, 200 gals.
Lime-sulphur, 5 gals.-4 gals.*
nicotine-sulphate, li pts.
Arsenate of lead, 8 bs.
Water, 200 gsls.
Srd Spray; larve in the cal>i cups and
on the leaves, petals falling.
Whale-oil soap, 10 lbs.
nirotine-snlphate, 1} pts.
Arsenate of lead, 8 lbs.
Water, 200 gala.
Lime-sulphur, 5 gals,
nicotine-sulphate, li pts.
Arsenate of lead, 8 bs.
Water, 200 gals.
•The alternative use of 5 or 6 gallons m this '-stance is determined by the season as well u by the
variety of the apple. The measures indicated the table are United States, which are related to
Imperial in the proportion of 5 to 4.
It must be realized that the suggested dates for the first and second sprayings
are merely approximate. They are considered suitable for such seasons as the
springs of 1916 and 1917 proved to be, and it will probably be found necessary
to vary the times of treatment in after years to suit conditions. The schedule
here presented has been drafted to indicate the procedure under two sets of
conditions, viz., a heav; and a light infestation of thripe. In cases of a light
infestation in an orchard where no material damage has been caused, and
in order to circumvent the possibility of the numbers increasing in later years,
a single spray of whale-oil soap mixture or miscible oil mixture is considered
all that is required for control purposes. The later sprays of lime-sulphur and
arsenate of lead are intended to combat apple scab mainly, and other orchard
pests. In a heavy infestation it is essential that the orchardist be prepared to
expend a great deal of energy in undertaking combative measures. The lime-
sulphur sprays for scab must be included as fourth and fifth sprays.
It is considered possible that, if an orchardist endeavours under such con-
ditions of infestation as have been experienced in the Saanich peninsula to
combat the thrips thoroughly, he will, possibly in one year, perhaps m two, be
able to adopt the .spraying schedule recommended for a light infestation.
Preparation of Spraying Mixtvres.
In order to dissolve the whale-oil soap warm water is desirable. Con-
sequently, it is advisable to construct a rough, open fire-place at some convenient
point in the orchard where water is readily available. When the soap has gone
entirely into solution, it is emptie<l into the tank of the spraying machine which
has been filled with the required amount of water. The requisite aniount of
nicotine sulphate and arsenate of lead is then measured out and added to the
solution. It is better to mix the arsenate of lead with water in a separate
vessel before adding it to the tank. The agitator is then set in motion,
enabling the ingredients to be thoroughly mixed. ,,.,.-
With all brands of oil sprays, it is essential that the directions for mixing sup-
plied by the manufacturers be at all times strictly followed, otherwise poor results
xM
^Z^t!%^^^^.^r^i^i^^^' Withmu.ibleoUNo.2, the amount
extent of two or t£L timift^o L/'?'.K'''^f^'*Pu**'^^^ »"<* '^^ter to ^e
tinual stirring is n^SsW Jntil irZ,^ *''^°?i" *''«° ^'^^'^ ""^ded. Con!
mdicated by the li JuidlLLS^'i c3v br"Swn'^.T°" Ku'^T'^' ^»>ich °s
fied is then added to the tank of thi !^^ • ° ^°}°^^- ^^« o" thus emulsi-
with water. Th7 agitator is t hi tf spraymg machine which has been filed
the tank thoroughl%S^ NlotineZthi?*° P'»V°*^ t»»e whole conten? of
arsenate of leadfthe lattS as in the case of^j! T^ ^''^l ^ 'V^ded, followed by
water It is well to T.mlZ:ri^:ti^;L^'iS^'^i^^^ ^^"^ ^"."^^'^ ^'^
of lead carries with it a certain peSSe of w.?Ln°""*"''^. ''"«n»t^
any chance the lead arsenate becomes Hrv*^l. n **®'^- Consequently, if by
made in calculating tKnount r^uTred ^' "' ^'°''''"''' '"' '^^ '*"* ^"«t »^
a«d iWar^^ful'lc^Xt;^^^^^^^^^ '\ «-ons of 1916
that the cost of the ingmlSt! nSs^v for ™i?^ sPfaymg.* It was shown
soap-nicotine-arsenate mixture br^Z^mShSL"*^ ^^T- »PP"«a«ons of the
from 13 cents to as much ^ 40 cTnte oer t^ T^^ ^'*"?t" ^'^«™°* ""'^"'Is
due to diflferences in the si^e of the trS t^hp 3^?i' •''''"''*'"!! '^^ ^^'o^" to be
per acre, to differences in the cost of iSu^ to t hff"* °!!?J?^'" °'. *''««" P'«°ted
of water, and to the degr^ of thoronJhni -^ accessibility or inaccessibilitv
further shown that the eSTor labo^Sr £e^ '" rnP'^''^ *^^ ^P^^' '* «««
each imnute, whether the power mSneswerT^nT»** *° """^ ^ two cents for
mg. Thus, it is import^t thTorrarXts sho^W T? T *''*."*"y «P™>-
necessary in refilling the tanks or in a„ vZ- °.°* ^^^^V 'onger than
incidental to sprayin| '"^ '" accomplishing the various operations
Types of Machines and Nozzles.
may be briefly stated that by farihe most^^H^' °/ ^''"P' ? »° "''^hard, it
employment of high-power, motor-driven m.tfif5**'*°',?; '^"x"'*" '^'^''^^ the
175 to 200 pounds pressure If hS-%we?ma?h'?S^ generating from
pressure than this are used, the mo^t eEvp^!-,?!.*' <^evelopmg a lesser
expected; and more than one aDoSion mU k "'*^ *'"^°* ^ reasonably
comparable to those received wher^ onll ^- ^^ ^fcessary to obtain result's
Wgher pressure, inasmS I^ the ^wer ^achS" *™''*.?'u""* '" '"'"^e under
shorter time and does it more efficiSy accomplishes more work in a
coarse, driiTglpray'^'fitSrafc^^^ "^I ^^ '« ^^ **"»* throws a
which throwa mCre spreaLg forS^Sf BDrr- *.f*° '°"°^ *•*** °°"'*'^
especially in the case Sf thosf .IS ^VeZ ^^ i5tVb"iroUS;S:
ACKNOWLEDGMENTS.
co-opTrltIJn\?lif V.^'l.T^^^ gratefully the cordial
Agr culture, and of his office™ MessreR^Mw**',' '^••o^n«al Department of
White assisted us in the cSvimr on of th^" ^"^°^ and E. W. White. Mr.
T A. Brydon, G. Stewit!"7d fa^er B?o«'^w1,^'\*- T""°°«- ^o Messr...
heir orchards for experiments spra^ng our Ct ?hi!fkr *'!l"*^ (?""?*'«« "'
late summer and autumn of 1917 Mr w n^!^ *"''* ""'^ .**"«• '^"'OK tiu-
the study of the soil phases of the work in Vh„?K^** ^'li employed to continue
other investigations ° *'** absence of both authors engaged on
•S«'
■ The Agri^ltural Gwett. of Canad,." Vol. 4. No. I, J„., 19,-
PP. 13-1«.
i.. .li-A.'. '^ *^-^ ;<f.»
51
REFERENCES.
1.
2.
•.i.
4.
.").
6.
7.
8.
10.
II.
12.
i:}.
1 1.
Foster S. W. and Junes, P. R. The life-history and habits of the pt!ar thrips
in California. U.S. Dept. Agr., Bull. 173, Wa.shinRton, 1915.
New California Thysanoptera. Entom. News, Vol. 15, No. 9,
The pear thrips. X.Y. A^r. Exp. Sta., Bull. 343, Geneva,
Journ. Eeon. Ent.,
Daniel, S. M.
1904.
Parrott, P. J.
N.Y., 1912.
Scott, D. M. The California pear thrips in Maryland.
Vol. 7, No. 6, Concord, N.H., 1914.
Ba^nall, R. S. A contribution to our knowledse of the British Thy.smoptera
with notes on injurious species. Jour. Econ. Biol., Vol. 4, No. 2, 1909.
Theobald, F. V. Report on economic zoologv for the vear ending Sept. 31,
1910. Jour. S.E. Agr. Coll., No. 91, \Vye,'l911.
Williams, C. B. Records anil descriptions of British Thysanoptera. Jour.
Econ. Biol., Vol. 8, No. 4, 1913.
Mokrzecki, S. .\. Report on injurious insects an<l diseases of plants in the
(lovernment of Taurida during the year 1912. Simferopol, 1913, pp.
1-23. Abstract in Rev. App. Entom., Ser. A, Vol. 1, 1!)13, p. 303.
WilHams, C. B. Biological and systematic notes on British Thysanoptera.
The Entomologist, Vr)l. 49, London, 191G.
Hood, J. Douglas. On the proper generic names for certain Thysanoptea of
economic importance. Proc. Fhit. Soc, Wash., Vol. lt>. No. 1, pp. 34-44,
1914.
Karny, H. Revision der von Serville aufgesteilten Thysanoptera genera.
Z(K)!ogi.sche Annalen, Bd. 4, Heft, 4, 1912.
Moulton, D. The pear thrips and its control. U.S. Dei)t. Agr., Bull. 80,
Part 4. Washington. 1909.
Foster, S. W. and Jones, P. R. How to control the pear thrips. U.S. Dept.
Agr., Cire. No. 131, Washington, 1911.
Felt, E. P. 29th Report of the State Entomologist. N.Y. State Museum,
Bull. 175, pp. 4.7-47, Albany, N.V., 1915.
*
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