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UNITED STATES DEPARTMENT OF AGRICULTURE
‘BULLETIN No. 903.
Coutdbition from the Bureau of Entomology
L. Oo. HOWARD, Chief.
Washington, D.C. PROFESSIONALLPARER=— April 22, 1921
By .*
.
W. M. DAVIDSON, Scientific Assistant, and
R. L. NOUGARET, Entomological Assistant,
Deciduous Fruit Insect Investigations
CONTENTS.
California History fe The Nymphand Winged Form ... .
Accidental and Natural Spread .. .. Nymphicals or Intermediate Forms
Distribution of Phylloxera in California . The Sexual Forms
Vineyard Destruction : The Gallicole and itS Relation to Cali-
Nomenclature and Synonymy of the fornia Conditions
Grape Phylloxera Effects of Water and Heat on Phylloxera
Biology of the Grape Phylioxera in Cali- Diffusion of Phylloxera
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UNITED STATES DEPARTMENT OF AGRICULTURE
BULLETIN No. 903 |
Contribution from the Bureau of Entomology ‘q
L. O. HOWARD, Chief
Washington,D.C. PROFESSIONAL PAPER April 22, 1921
THE GRAPE PHYLLOXERA‘ IN CALIFORNIA.
By W. M. Davinson, Scientific Assistant, and R. L. Nougaret,’ Hntomological
Assistant, Deciduous Fruit Insect Investigations.
CONTENTS.
Page. Page
California WMiStory. 22s = 6 ees Se ets 1 | The nymph and winged form_______ 73
Accidental and natural spread______ @ | Nymphicals or intermediate forms__ 82
Distribution of phylloxera in Cali- RHeESexUc TOM Se. s ee aeee le eis 90
RO: Aaa hes Per Ee Te ie 11 | The gallicole and its relation to Cali-
Minevardudestructione.. ) =. eon = 15 THOMA (COMA NMOS ee 95
Nomenclature and synonymy of the Effects of water and heat on phyl-
crape phylloxeras aie eee 26 LORCA Pa Ee Ce Ne Bis CE Oe AT eae 98
Biology of the grape phylloxera in DittusionsoL phylloxera=s 4a" ass ~ 100
Calitormiayeeee ssa 2 eae I 20 | Summary.= == eee Pema de 122
Mhesradicicoles2 2s Paseo ee he Ait aces onde: elirexole IAL
CALIFORNIA HISTORY.
EARLY VINE PLANTING IN CALIFORNIA.
The grape phylloxera is not native to California. It has long
been recognized as originating in North America, but its native
habitat is east of the Rocky Mountains. The insect has not established
itself upon the native vine of California (Vtis californica) in the
wild state, whereas in Arizona it is established on native vines.
1 Phyllozera vitifoliae (Fitch).
* Now in charge, Viticulture Service, California Department of Agriculture, Sacramento,
Calif.
Notse.—In connection with other work in California, the office of Deciduous Fruit
Insect Investigations, Bureau of Hntomology, in cooperation with the Bureau of Plant
Industry, has been engaged in an investigation of the grape phylloxera during several
years past, with principal headquarters for the work at Walnut Creek. The work
inaugurated by E. L. Jenne, upon his death was taken over by S. W. Foster, assisted by
R. L. Nougaret. Upon Mr. Foster’s leaving the service, the investigation was continued
by Messrs. Nougaret and Davidson, the latter giving especial attention to biological and
life-history studies and the former to investigations in the field and to remedial opera-
tions. The present report deals with the history, injuries, and life history of the insect
in California. Remedial measures will be made the subject of another publication. It
has been necessary to omit an extended bibliography of thé subject.—A. L. QUAINTANCE,
Entomologist in Charge of Deciduous Fruit Insect Investigations,
1900°—21——_1
bo
BULLETIN £03, U. S. DEPARTMENT OF AGRICU! TURE.
More specifically, the insect is a native of the Mississippi Valley,
where the vines have developed a resistance to phylloxera, and such
species as Vitis riparia, V. rupestris, V. aestivalis, etc., thrive, not-
withstanding the presence of the insect. These wild species possess
varying degrees of immunity and threugh scientific selection and
hybridization have yielded types of vines possessing inherent de-
grees of immunity. known to viticulture as resistant vines, or re-
sistant stocks when designated as a root upcn which to graft com-
mercial yarieties of grapes in order to circumvent the ravages of
phylloxera.
Vitis californica is a wild species of vine found not only in Cali-
fornia but throughout the Pacific coast. Because normally found free
of phylloxera in its wild state, it was at one time tried out as a
resistant stock upon which to graft commercial varieties, but proved
a complete failure in all but one or two instances. Even under normal
conditions and environment, when once attacked it succumbs to the
injury by the insect.®
The Mission grape is a cultivated variety of Vitis vinifera, and
although of European origin, its introduction to the Pacific coast is
so intimately related with the first settlement of California under
Spanish rule that it well deserves the oft-attributed title of * Cali-
fornia grape” (7)*. The Mission grape was introduced into Cali-
fornia by the Padres of the Roman Catholic missions. As early as
1524 (18, p. 17), while Cortez was governor of Mexico, then called
New Spain, seeds and plants were most often part of the cargo
of vessels plying between the mother country and her colonies.
Grapes and olives are plants mentioned as being among these. It is
to be assumed that about that time JV Ztis vinifera varieties were intro-
duced into Mexico from Spain® through both cuttings and seeds
(1, v. 2, p. 181-133; v. 3, p. 613).
3In the Annual Report of the California Board of State Viticultural Commissioners
for 1887. published in 1888, pages 47-48. may be found the following: “‘ While visiting
Mr. Hasan vineyard, we were led to examine an old vine—V. californica—which
TOPE SL like one infested with phylloxera. This surmise proved correct * * *.
“The commission has often sought for evidences of phylloxera on our wild yines in
their native state, but up to this time nene has been feund, this being the first case of
the kind discovered.*” (See ‘* Literature cited (5).” p. 127.)
+ Numbers in parentheses refer io “‘ Literature cited.“ p. 127.
>In this connection F. T. Bioletti, professor of viticulture at the University of Cali-
fornia, writes as follows: “* No one has yet been able to trace the Mission grape with
certainty to any European variety. It is a remarkable coincidence, if nothing else, that
a Sardinian grape known as the Monica resembles the Mission very closely. The Monica
is said to be a favorite grape of the monks in Sardinia, and it seems probable that the
missionary monks of Mexico, finding it difficult to transport cuttings from their original
homes, obtained seeds of the grape which they liked the best and that from the seedlings
grcwn they chose the one which most resembled the grape they were looking for. If this
is in accordance with the facts, the Mission is simply a seedling of the Monica.”
He further advances the suggestion that the Mission might be a seedling of the Monica,
as published in a report (2) of the viticultural work of the agricultural experiment
station of the University of California * * * 1887-1893.
THE GRAPE PHYLLOXERA IN CALIFORNIA. 3
Later, in the early part of the eighteenth century, a long hne of
missions was established throughont the peninsula of Lower Calig
fornia, the Mission of Loreto being the first, in 1697. These missions
all grew grapes. The vines were furnished to them originally by
the colonies of Mexico. As missions were founded, products and
plants were furnished to the new one by the older established ones,
and grapes are almost always mentioned as being cultivated by the
Padres.
The Mission of San Diego was the first to be founded in upper
California, and the vines planted there were brought from the mis-
sions of Lower California. As no other variety but the Mission
grape is known to have been cultivated by the different missions
which were founded in after years, it is to be presumed that it was
introduced into this State with the founding of the Mission of San
Diego, 1769.
The Mission is a long-lived, vigorous, and thrifty vine, as is
attested by two remarkable specimens. The one planted in 1775, and
still living, is on the property of the San Gabriel Mission in Los
Angeles County, is trained on an arbor, covers 9,000 square feet, and
its trunk just below the surface of the soil has a circumference of
9 feet. The other, planted in 1842 near Carpenteria, died in 1915,
presumably of the “Anaheim disease.” It measured at its base 84
feet in circumference; at a height of 64 feet it divided into three
branches, one of which measured 34 feet in circumference. As an
arbor it covered one-fourth acre. and in 1895 yielded its maximum
crop of 10 tons, its average crop being estimated at 5 tons.®
The Mission grape in early days was planted by the Padres around
the missions and was used both as a table grape and especially for
making wine. Gen. Vallejo (7) is authority for the statement that
the Mission grapes grown at the Sonoma Mission were of a better
quality than those grown at the other missions in California, and
that a recognized superior quality of wine was made from them.
It was probably because of this reputation that the first commercial
vineyards of wine grapes were established in the vicinity of the town
of Sonoma. In this district the grape phylloxera was first discov-
ered, and the dying of the vines, which for some time had puzzled the
viticulturists, was finally determined to be the result of this insect’s
attack. An importation of vines from Europe of unparallelled im-
portance up to that time for California, and one which may ade-
quately be termed a “pioneer importation,” occurred at about this
time and very shortly prior to the discovery in France of the
phylloxera, thereby furnishing grounds for the subsequent report,
more or less widely spread throughout the State and which persists
® Details of its history can be obtained from the secretary of the Carpenteria Chamber
of Commerce.
4 BULLETIN 908, U. S. DEPARTMENT OF AGRICULTURE.
even at this late date, though refuted at different times by investi-
ators, that this importation of European vines was responsible for
the introduction of phylloxera into California. This is a mistaken
idea. The history of the grape industry virtually proves that the
insect was imported with American species or varieties of grapes
from east of the Rocky Mountains.
FIRST DISCOVERY OF GRAPE PHYLLOXERA IN CALIFORNIA.
The first evidence of phylloxera infestation in California dates as
far back as 1858. The dissemination of phylloxera continued for
years in California before the existence of the pest was known, al-
though its destructive work was observed, commented on, and desig-
nated a disease of vines from unknown causes. Reference to the
first discovery and determination of the insect in California is to be
found in a report (4, p. 108-111) dated August 28, 1880, and sub-
mitted by H. Appleton. In his report the first ravages witnessed in
California are discussed, and from them is inferred the date of in-
troduction of the insect. Extracts from this report follow:
On the nineteenth of August, 1873, an insect was found on the roots of
grapevines by H. Appleton and O. W. Craig, in the vineyard of the latter,
situated two miles north from Sonoma Town, on the west side of Sonoma
Creek. An investigation was ordered at the time, for though the insect was
identified as “the insect, or louse, known in Europe by the title of phylloxera-
~ vastatrix, and in the United States as pemphygus vitifoliae,” there existed a
doubt in the minds of the investigators, because the injury was confined wholly
to the roots of the vine, and no symptoms of injury such as recorded in
Europe and in Eastern North America could be detected on the leaves.
From information received from Mr. A. F. Haraszthy and Captain E. Cutter,
Superintendent of the Buena Vista Company’s vineyards, I am able to give
the following facts in regard to their large vineyards:
A vineyard of about one thousand vines was planted in 1834-385, and was
watered every year. In 1850 and 1852 the vineyard was largely increased, and
the system of irrigation was stopped. In 1857 about two hundred thousand
vines were set out, and in 1858 one hundred acres were put in yines (six
hundred and eighty vines to the acre). Again, in 1860, fifty acres were
laid out. In 1862, Colonel A. Haraszthy planted 70,000 European vines, and
it was among these vines the disease increased most rapidly.
In the Spring of 1863 the Buena Vista Company was incorporated, and in
the Spring of 1864 that company planted 100,000 vines.
As early as 1860 decayed and dying vines were noticed in the vineyard, and
they were taken up and others planted in their places. An examination was _-
made to discover the cause of the disease in these vines, and it was attributed
to alkali water, which was found a few feet underground. ‘The roots were de-
cayed. No examination by microscope of these roots was made. Vines
died from time to time, showing short growth, small and colorless grapes,
early yellow leaves—in fact, all the symptoms were olserved of vines dying
from the vine pest.
In 1868 about 3 acres of diseased vines were taken up (planted in 1850)
on the north side of the dwelling house, and new vines planted, which grew
well, showing little signs of decay till they were four years old, at which
time (1873) the Phylloxera Committee, of the Viticultural Club, found =
phylloxera on several vines.
THE GRAPE PHYLLOXERA IN CALIFORNIA. 5)
The facts of this statement are significant and by no means am-
biguous if considered in the light of the knowledge possessed to-day
of the life history and habits of phylloxera, the nature of its in-
jury, and the progress of its ravages.
This report also indicates how and when the first impulse was
given to the development of the grape and wine industries of the
State, then in their infancy. As interest grew in this direction,
better varieties of grapes than the Mission would naturally be sought
and given a trial. This was the case with the eastern variety of
grape, the Catawba, a vine susceptible to the attack of phylloxera
because of its fleshy roots and successfully grown at that time in
the East as a wine grape. A weekly agricultural paper, the Cali-
fornia Farmer (6), under date of Thursday, January 23, 1855, in an
editorial article entitled ‘“ The Catawba Grape,” says:
We sincerely esteem the Catawba grape, one of the very best varieties for
cultivation in California. Longworth of Ohio, whose famous Catawba Cham-
pagne is now esteemed equal to any wine imported, says it is the very finest
wine grape known. Will be found far superior to our California Grape [Mis-
sion]. We earnestly urge our cultivators to give the Catawba a careful trial.
The same agricultural periodical from time to time that same year
published other articles’ eulogizing not only the Catawba but also
other vines of eastern varieties and quoting fabulous yields in wine
and profits.
Articles such as these undoubtedly influenced the planting of east-
ern varieties, if only as an experiment. Can it be doubted that many
vines were brought from the East to California and the phylloxera
introduced with them ?
The variety of grape planted in 1850-1852 in the Buena Vista
vineyard is not mentioned. It is more than likely that the major
part of the planting was of Mission. If these vines were inoculated
with phyloxera shortly afterwards by means of a few eastern grape-
vines planted near by, the vineyard would have experienced a spread
of invasion as related above by Appleton. Evidence of the insects’
injury would be apparent as affecting only a few vines during a few
years or up to about 1860, and eight years later the vines, covering
an area of 3 acres, would have become so dwarfed and nonproduc-
tive, with perhaps a few dead, that it would be necessary to grub
them up. ‘That this vineyard trouble was due to phylloxera is em-
phasized by the further statement that the 3 acres were again
replanted with new vines, and during the four following years
(1869-1872) the vines were again affected in a similar manner, but
to a slighter degree, just as a recurrence of infestation would act if
vines were planted in infested soil. Finally, in 1873, just five years
7H. g., “ What are the best grapes;”’ “ Extracts of the Cincinnati Gazette.”
6 BULLETIN 903, U. S. DEPARTMENT OF AGRICULTURE.
after the replanting of the 3 acres, the committee of the Viticultural
Club discovered the phylloxera on the roots of several of the replants.
The history of this vineyard proves conclusively by direct and cir-
cumstantial evidence that the trouble was due to phylloxera. It
localizes the infestation, describes the progress and spread of the |
injury, and, by fixing dates, determines the period of time the prog-
ress covered. Finally, the presence of the insect is discovered and
its identity determined. — |
In 1861 Gov. Downey, of California, appointed three commis-
sioners to work in the interests of the grape industry, two of the
members of this commission being Don Juan Warner and A. Ha-
raszthy. The latter was sent to Europe to purchase for the State
for distribution different varieties of grapes, and the result was the
importation of 200,000 cuttings and rooted vines, comprising 1,400
different varieties of grapes from all the vine-growing countries of
Europe and also from Asia Minor. It may be that some of these im-
ported rooted vines harbored phylloxera, which already had caused ~
considerable damage to vines in France, although the insect was only
discovered in that country the following year (1862). It is quite
likely that a good portion of the 70,000 vines planted out on the
Buena Vista vineyard in 1862 and referred to in Appleton’s report
were propagated from this importation and that the pest may have
been introduced simultaneously with the planting of the vines. The —
rapid destruction of the vineyard, as stated, however, could have been
brought about in the case of the young vines just as well by infesta-
tion communicated by the old vineyard.
The history of the Orleans Hill vineyard furnishes an insight into
the methods of establishing vineyards with varieties of grapes im-
ported from Europe in the early days of grape culture in California,
and helps to give grounds for the belief that the earliest and original
introduction of phylloxera into this State was due to eastern varieties
of grapes only.
Data of this history are contained in a report, dated 1880, submitted
by the owner of the vineyard (4, p. 112). In 1853 the owner im-
ported from Nassau, on the Rhine, in Germany, 15 varieties of grape
cuttings (vinifera) and planted them in his garden near Sutters
Fort, Sacramento, where they flourished splendidly and showed no
signs of disease. In 1859-60 many vines were propagated here for
planting the Orleans Hill vineyard in Cache Creek Canyon, Solano
County. This vineyard was set out*in two different situations, part
being on a hillside and part in a flat. In the latter situation the
soil was of a stiff clayey nature and the vines did not do as well as
on the more friable hillside soil, and this necessitated replanting, for
which there were procured later from Napa some Zinfandel vines.
THE GRAPE PHYLLOXERA IN CALIFORNIA. 7
The date when these replants were procured is not specified, but was
probably about 1864 or 1865. Before the date of replanting the
phylloxera had infested the Sonoma Creek district and had spread
to Napa County. ,
In 1859 a horticultural exhibit was held in the agricultural hall
just completed that year’at Sacramento, and the records of the State
Agricultural Society mention exceptionally good exhibits of grapes
by progressive fruit growers. The eastern grape Catawba is twice
mentioned. !
From another report (4, p. 29-30) we learn to what extent the
eastern varieties of grapes were grown prior to 1875 in El Dorado
County. No mention is made of earlier dates, but it is more than
probable that the European grapes were already supplanting the
eastern ones, judging by the few of the latter type which were
planted in later years and which to-day are found only in family
vineyards and gardens. This report, written by Mr. G. G. Blan-
chard, commissioner of the State board of viticulture, further stated
that what was true of Kl Dorado County could also be said of
Nevada, Placer, Amador, Calaveras, Tuolumne, and Mariposa Coun-
ties. A passage reads:
The proportions and kinds (grapes) growing, taking one hundred as the sum,
are as follows: Mission, or native grapes, sixty-eight; Catawba and Isabella,
ten; White Muscat, Muscatella, Malaga, six; Tokay, Black Morocco, Malvoisies,
one; Zinfandel, Riesling, two. The other thirteen are made up of numerous
other varieties, such as Sweet Water, Black July, Hartford Prolific, Cloantha,
and Concord, and some others.
In this enumeration eastern grapes would represent approximately
23 per cent of the varieties grown. We thus see the important part
played by eastern varieties of grapes in the earliest plantings and
can conceive how the pest was introduced directly from its natural
habitat.
ACCIDENTAL AND NATURAL SPREAD.
Centers of infestation, when compared according to the modes of
dissemination which they engender, are of two kinds: Accidental
and natural. An accidental distribution center would be a nursery
which imported, unwittingly, phylloxera-infested grapes, propagated
the vines, and by so doing bred the insect and disseminated it with
the sale and shipment of these vines. The same is true when vines
are procured from phylloxera-infested districts. For new plant-
ings or replants, such a center would be the infested locality in Napa,
from which the Zinfandel vines were the means of introducing the
pest into a locality as yet free from it. In turn, the Orleans Hill
vineyard became a natural distributing center because the insect
by its natural increase and habit spread to other parts of the same
vineyard or even to other vineyards of the district.
8 BULLETIN 903, U. S. DEPARTMENT OF AGRICULTURE.
Infestation from accidental distributing centers may be avoided
by strictly enforced quarantine measures.
Accidental spread has been the main cause of most of the phyllox-
era infestation throughout the vineyards of California because of
its being an initial inoculation, developing later into a center of
natural dissemination. |
A general survey of the growth of the grape industry, which
at times, as in the late eighties and early nineties, attained the
proportion of a boom, furnishes an indication of the accidental
spread which took place concurrently.
Cuttings were used almost exclusively for planting vineyards in
preference to rooted vines, the latter being used for replanting
“misses.” and even then not commonly used. As will be shown
later, there is little, if any, danger in disseminating the phylloxera
from cuttings, unless these are heeled in in infested soil while await-
ing shipment. It is for this reason that the accidental diffusion
was greatly restricted. If rooted vines had been commonly used,
originating from the same district as the cuttings, the accidental
diffusion would have been so general as perhaps to have precluded
before long the growing of vinifera vines on their own roots.
THE WINGED MIGRANT NOT A FACTOR IN SPREAD UNDER CALIFORNIA
CONDITIONS.
Profiting by the investigations and experiments that were being
carried on in France, the University of California in conjunction
with the State Board of Viticulture made extensive efforts to ar-
rest the ravages of the phylloxera, and made investigations pertain- —
ing to its life history and habits. These deserve special mention
in this report.
Dr. F. W. Morse (16) of Oakland, Calif., during the period
1881-1886, as an assistant in the General Agricultural Laboratory,
discovered in the course of his investigations on August 26, 1884,
specimens of the gall louse or leaf-inhabiting form of the phylloxera.
As is noted under the heading “ The gallicole and its relation to
California conditions” (p. 95), this is the only recorded instance
of the finding in California of the leaf galls. In this connection it
may be said that in the experimental vineyards of the Bureau of
Plant Industry, United States Department of Agriculture, in which
are collected many varieties and hybrids of species of American
vines, not a few of which are susceptible to leaf galls when culti-
vated in the Eastern or Middle States, an exceptionally good field
for observation is offered. Mr. G. C. Husmann, under whose direc-
tion these vineyards are conducted, states that the leaf gall, to his
knowledge, has never been found inthem. Extensive correspondence
THE GRAPE PHYLLOXERA IN CALIFORNIA. 9
with entomologists and prominent viticulturists in California elicited
the same information.
Laboratory experiments, conducted under favorable conditions to
obtain winter eggs with the existing strain of phylloxera in Calh-
fornia, have failed to go beyond the production of the winged form
in soeguile: devised cages, although in other laboratory experiments
the sexed forms were produced and the discovery in the natural state
of a single winter egg must be mentioned.
A study of the hfe history has corroborated the observations of
Dr. Morse relating to the sterility of a portion of the winged migrants
and to the sterility of some and the debility of the remainder of their
progeny. The writers’ observations demonstrate that the normal life
cycle of the insect in California is wholly parthenogenetic and that
the natural spread, or diffusion, is due entirely to young radicicole
larvee possessing migratory instincts, at least during July, August,
and September, and to which has been given the name of “wan-
derers” to distinguish them from “migrants,” a term which com-
monly is applied to winged forms of the Aphididae.
The conclusions of the investigations of Dr. Morse point to the
possibility of such a condition, though not affirming that the winged
migrant is not responsible for the diffusion of the species in Cali-
fornia. The late Prof. KE. W. Hilgard (14) shared this view, which
he expounded in his report, in which he indicates the discovery by
him of one of the first phylloxera spots in Napa Valley, as follows:
The first phylloxerated ‘ spot’ within the Napa Valley was observed by me
in 1877, close to the stage road and public highway leading directly from the
worst-infested portion of Sonoma, and on which vineyard material was, and
is, constantly being hauled back and forth. It is plainly from this highway
and its infested wagonloads that the insect has spread in the Napa Valley.
The “spot” alluded to is believed by the writers to have been
either in the old Squibb vineyard (10 acres), in the old McClure
vineyard adjoining, or in the Callan vineyard (50 acres). All these
were located close together. They have long since been pulled up,
the land is now pasture, and only a very few of the old original
vines still exist, although browsed down by the stock. These vines
date back to 1866.
From present knowledge of the biology of the phylloxera, it is be-
lieved by the writers that the vineyard material referred to by Prof.
Hilgard was responsible for the spread of the pest to this location,
but the inoculation was due to the wandering young radicicole
larvee rather than to the winged form.
PHYLLOXERA SPREAD BY PICKING BOXES.
“Vineyard material” may imply many sources of infestation.
Besides rooted vines, grape-picking boxes are very likely to trans-
10 BULLETIN 903, U. S. DEPARTMENT OF AGRICULTURE.
port the insect from one district to another. At times grapes are de-
livered to the wineries in greater quantities than can be handled,
and boxes of grapes are unloaded and left at the winery instead of
their contents being emptied into the elevators and the empty boxes
returned to the same wagon. Boxes are exchanged, and some from
infested districts find their way to uninfested vineyards. Wander-
ing larvee (wanderers) easily shelter themselves in cracks and joints |
of boxes while these remain strewn throughout the vineyard waiting
to be filled with grapes, and when the boxes are transferred to other
vineyards, after having been emptied at the winery, the insects may
be released by the shock of the empty box against the ground in
the process of unloading.
In their practical experience, certain grape growers have noticed
that the first signs of phylloxera in their vineyards appear at places
where they have been in the habit of dumping boxes for the con-
venience of grape pickers.
There were a number of wineries, reputed for the excellence of
their wines, in the early-infested district around Glen Ellen, Sonoma,
and Los Guillicos, and grapes were hauled to them from afar at
about the time vines were dying rapidly in their vicinity. This
accounts, no doubt, for the several early centers of infestation which
appeared in a short period of time in Napa County.
The pest spread into Napa County from Sonoma County not only
along the highway to and beyond the vineyards cited in Prof. Hul-
gard’s report, but also over the ranges of hills referred to in the same
report by means of a mountain road which ran over the divide from
Sonoma and descended into a long narrow valley (Brown Valley),
which itself opened out into Napa Valley quite close to the city of
Napa. At the head of Brown Valley and almost on the county
boundary line is the Dell vineyard. From the owner, Mr. C. Dell,
the following information was obtained: In 1867, 20 acres of Mission
grapes were planted with cuttings obtained from the Wing vineyard
(then owned by Buhman Bros.), material for which formerly had
_ been secured from the Buena Vista district at Sonoma. After seven
years the Dell vineyard began to show signs of phylloxera in small
patches, but bore good crops for four years. The Wing nee
located close by, began to die at the same time.
The phylloxera was introduced in this case probably by means of
picking boxes, or else by rooted vines planted to fill out places where
the cuttings fed failed. If the dates are correct, the infestation
would have been noticed, without the cause being known, in 1874, or
about the time it was discovered along the Sonoma highway.
The above data are recorded to indicate how important a role this
Sonoma Creek district played in the first introduction of the insect
into California and how the spread occurred through different chan-
THE GRAPE PHYLLOXERA IN CALIFORNIA. uh
nels. For this reason the early plantings give an idea of how the
insect could have been spread before its presence was suspected.
PRACTICAL METHODS EMPLOYED TO ARREST THE SPREAD OF THE PEST.
When the discovery of phylloxera in California was first made
known, the grape growers were already acquainted more or less
with the havoc it had produced in the vineyards of France, and a
panic spread throughout the different grape districts. It soon sub-
sided. however, when the vineyards were not being rapidly destroyed,
and even precautionary measures were overlooked.
Of all the grape-growing counties, that portion of Alameda County
known as the Livermore Valley district evolved the best organized
system of quarantine measures, the aim of which was not to prohibit
the importation of vines into the county, but to have cuttings, as
well as rooted vines, thoroughly disinfected before they were per-
mitted to be planted.*®
The disinfectant used was a commercial soluble phenol. Vines
were immersed for one-half hour in a solution of 1 part phenol to 60
parts water. Notwithstanding these precautions, vines were intro-
duced without the knowledge of the quarantine commission, and
there occurred three distinct centers of infestation from which the
pest was remarked to spread with the prevailing summer winds.
Two of these centers were planted originally with material from
San Jose, and the third with vines from St. Helena, in Napa County.
DISTRIBUTION OF PHYLLOXERA IN CALIFORNIA.
As far as has been observed, Stanislaus, Merced, Kings, and Madera
Counties, north of Tehachapi Pass, are free from phylloxera. South
of Tehachapi Pass it has not been found so far. Most of the counties
named have either enacted ordinances establishing prohibitive quar-
antine against the importation of grapevines or protective measures
subjecting vines to strict inspection and fumigation.
The absence of infestation is without doubt not wholly due to
quarantine measures, which were enacted years after the pest had
many opportunities to be introduced, but more likely is due to the
combined conditions of climate and soil in these counties.
The writers have made a personal investigation of the present status
of phylloxera infestation, and have tried to ascertain and estimate
approximately the damage caused to the viticultural interests. At
this late date, however, there is much difficulty in obtaining informa-
tion on which to base the estimate. Quite a number of vineyards have
been replanted, some as many as three times; property has changed
hands, and the history of vineyards has been forgotten. Again,
8 Data personally contributed by Charles A. Wetmore, formerly chief executive of the
State board of viticultural commissioners.
12 BULLETIN 903, U. S. DEPARTMENT OF AGRICULTURE.
no traces exist of large vineyards pulled up but not replanted,
and thus accurate data are unobtainable. Therefore a summarized
statement based upon data to be found in the various reports of
18° AT? “sé
UN wo we YARDS.
Ee] WAESTATION DOUBTFUL.
COUNTY HAVING LESS THAN
250 ACRES. OF VINEYARDS.
NOT INFESTED,
ALIFORNMIA
| SCALE-STRTUTE MILES
ONES TS0= 9S ea 75-
e a i f Ur 4 wresrto since ee
a We ee fle St» QURING PLAIOD 1890-1900
59 2 oe ize Sep fk Bs} 1 DURING LERIOD 1680-1890 |»
eon cnt neat ly | Draenei eer rs m DURING FERI¢D [875-1880 |
Fic. 1.—Map indicating progress of phylloxera infestation in California. The map does
not show the severity or degree of infestation. Counties having less than 250 acres of
vineyards were not inspected. In those counties marked doubtfully infested inspection
took place at a time of year when the insect was difficult to detect ; none were found
but the aerial growth of the vines suggested phylloxeration. In the counties of Kings,
San Benito, Merced, Stanislaus, Calaveras, Amador, and Tehama no phylloxera was
found at the time of inspection, but they should not be deemed to a certainty free of the
insect.
the State Board of Viticultural Commissioners and other agricul-
tural and horticultural reports is presented. This, with the aid of
a map of California (fig. 1) to indicate infested counties in shad-
THE GRAPE PHYLLOXERA IN CALIFORNIA.
13
ings to correspond to a period of years within certain dates, will
enable one at a glance to conceive the degree of injury produced
and the loss sustained by the viticultural interests.
A general idea can be formed of the growth of the viticultural
interests of California and correlatively of the economic importance
of the grape phylloxera by comparing the report on grape produc-
tion of the State statistician for the year 1914 with the report of a
similar nature for the period 1856-1866 (Table I).
TABLE I.—Planting of vines in California in different perods.
County.
SUG EO ae eee reson:
Mier Codes ssn sees ee
Sane emanrdinOze =e eee
NaneDiceOeeeeseeree Recenonse ce
Sanelran CISCOMs- ese aps el | Pe ee
San JOagiinea sect) Lae Ee
San Luis\Obispo-=..-2)2.-2)2-
SamyMateoses-ec-n ho ooeecoe
Salley Clan ae nese er
SantanCnuZ see eee
Solan Osea ete eee a POs
SUUCCE ya ese eens here
Orange ysis see ea
UV ORSIGO-e ce aon ee Asoo See
MOTD URS ae ae he eos tn
Total number of vines...
Motalacress.s--.-0 aoe
Vines planted in— n
Pp Total bearing Total
vines vines vines
existing exictin g existing
1856 1857 1858 a 1869207 |= iniigegs. |) sv 1910:
48,000 | 125,000] 175,000] 1,575,000] 155,070] 2,390,959
9,000 8,000 20,000} 180,000] 757,773 314, 604
15,000 45,773 80,707 | 726,363 | 369,785 258, 742
6) 465 24,187| 217,665| 515,049 212' 300
10, 000 4120 4,285 | 36,000 47; 800 482) 417
75, 000 4) 468 42) 640 83,760 | 201,51 2,972, 1:
1,056 Q? 450 190 eens
6, 390 26, 400 77,472 | 697,248 | 1,441,039 581, 342
2).000 1, 000 3,000 27 000neueeeiaew 40, 687, 207
800 500 915 8, 235 839 ; 095
yo SS SP BEDI OS IND NOD C5 TOGO IO COCO II COL 1.000 HARE SSI 2.000 CH el te 18.000 os 252 39, 478
0 OE ig eee ae
LGU ens igs We Eee aD d i ; 11,000) 296, 752
CREED OF ICN PICO OC IY CY KOO OOOO OH IDO DD OOO Oi SG 2 2
Dae Ne a CR 200 31
726,000 | 600,000 | 1,650,000 | 14,850,000 | 3,000,000 | 4,923,877
500 600 5, 400 11, 542 115, 198
1,000 15, 227 15,000} 135,000 51, 783 28, 647
10, 000 15, 000 15,000} 135,000} 100,740 | 1,281,342
10, 000 11, 650 50, 000 50, 000 84) 839 79, 935
22)700 55,000 90,000 | 810,000 | 1,166,935 | 8, 595,338
52a 6,000 8, 000 72,000 |” 124,000 94) 338
: (742 000 45,000] 397,101] 1,340,132
800 400 3, 600 1 BUCK Masao
52,200 | 119,500] 327,900 | 2,951,000 | 951,315 | 7,627,510
80, 000 38, 000 75, 000 675, 000 312) 562 987, 127
4 ; 50, ;,000 1,915 | 1,228,858
1, 200 1, 000 9,000 75 3,000
13, 467 28) 640 40,000 | 4,112,792 | 493,387] 13,371,794
1, 500 2; 000 10, 000 90, 000 18, 263 265, 481
15,000 40,000 40,000 | 360, 000 16, 000 124, 990
; 000 ,000 | — 810;000 | 220; 000 208, 595
150,000 | 500,000 | — 513,000 | 4,617,000 | 2,0007000 | 5,584, 480
5,000 6,179 20, 000 56,000 | 2187100 | 1,365, 418
5,348 6,100 25,000 225,000 | 1, 534, 520 117, 481
; 4 ” 500 A787 lees FAS
1,000 1; 000 2,000 | 180, 000 8,469 2, 473
56, 178 50,000 52, 869 554,178 950,600 | 1, 213, 265
61,590} 170,508 | 187,621 | 2,000,000 | 2,830,195 | 18,864,163
4) 420 3,020 1,800 | 162,000} 112310 | 1,932,302
45,123] 135,369 50,000 | 450, 000 163,663 | - 1, 249, 923
iz 2, 000 5, 800 49,500 | 145,883 | 1,307, 218
359 19, 096 2) 842
ai SES Tae ot ” 400 30,000 | 270,000] 100,950 | 7,227) 491
9, 858 29, 891 57,520 | 517,734 | 505, 250 95, 811
26, 902 61,903 | 155,425 | 1,398'825| 157/434] 2,568,019
28,000 30, 000 50,000 | 450,000} 494) 472 162,751
ae BOR Ae Reprod ERD e ig capil ge nolg Tha we ped 9,000
sabes OS ods a RSE ta ee Na 20, 416
ees aun Gre ay Cay Alle vera is |S sledaaoary lees An) ce 298” 813
Sie oo ie a halo pana [eee cA tll ray Oh a Wh a A 419, 582
Se aries al eran nea een enero ms Men SEER err oder |) «2/898. 730
Dee che esc | choles Seat oem NG gn War a er 795
Ee MMN RON e enn abo Tiled om Tan 2, 000
2 aoe Le ie allo ce oe aS a a ee 282° 682
a enmn Wee MUNN A Re apwik Virdee Ce 2; 1, 570, 794
Penne im aa Meas alae ie: 177,976
Sait selsc Bal] s 6 Se, sgh eel by ge ER |e Mie ae a Ra 1, 530, 630
Lock gen boeudl oocls Le ti abel eo al nea ae IIa UO re i nt ane 36, 398
1,540,134 | 2, 265,062 3, 854, 548 40, 172, 654 | 19,695,814 | 139,099, 560
2 sa ie a 41 9,077 98966. |.2. 5. eae
Total
14 BULLETIN 903, U. S. DEPARTMENT OF AGRICULTURE.
At this earlier period the pioneer growers of grapes were begin-
ning to realize the possibilities of success due to the advantage of the
peculiar suitabilities of climate and soil in California for the culture
of European varieties of Vitis vinifera.
Within the period of 48 years (1866-1914) there had been an
increase of nearly 90,000,000 vines. Within this lapse of time, so
comparatively short for such a prominent industry of the State,
many changes occurred in the different viticultural districts with
which phylloxera had little or nothing to do, and the gradual damage
and loss caused by the insect could not be compared with the acutely
sinister influence of extreme fluctuations in the market values of
grapes, whether for wine, raisin, or table use, which swayed the
industry at different times from opulence to ruin and vice versa for
the growers; yet when looking backward over the years, the phyl-
loxera stands out preeminent and is considered as the main single
factor in the loss and damage sustained by California viticulture.
In the early period the counties south of the San Bernardino
boundary line were in the lead for the acreage in vines and for the
production of wine. ‘To-day in these counties viticulture is of sec-
ondary importance, yet phylloxera has never been discovered there.
The Anaheim disease was one of the causes of this decline, but the
change to the more lucrative investments in citrus culture, which no
doubt appealed more to the tastes of the many eastern settlers who
largely populated that portion of the State, is mainly responsible for
the falling off in acreage of grapes and lack of interest in the industry.
Another viticultural district which underwent a great change was
that of the Santa Clara Valley. There grape growing increased
rapidly from 1885 to 1895, when the acreage of vineyards was the
greatest and the county of Santa Clara produced almost one-third
of the dry wines of the State. From 1893, when the vines began to
die, the decline in acreage was much more rapid than had been its
growth.
It was commonly believed at the time that the Anaheim disease,
which had caused such great ravages in the southern part of the
State, was also responsible for the sudden dying off of the vines in
the Santa Clara Valley. The damage caused to the vineyards was
so extensive that an investigation was instituted by the College of
Agriculture of the University of California to determine the
cause (3). The general conclusions arrived at were the following:
First, that the dying vines exhibit symptoms differing materially from those
shown by the vines in Southern California which were destroyed by the Ana-
heim disease; and, second, that whether or not there be some “ unknown in- —
fluence’ at work, as suggested by Mr. Newton B. Pierce, the real, determining
factor is the deficiency of rainfall during the years 1897-1900.
:
:
THE GRAPE PHYLLOXERA IN CALIFORNIA. 15
At this time the phylloxera was known to exist more or less
throughout the valley, and had been identified in different vineyards,
but as yet its injury had not reached the advanced stage of noticeable
characteristic phylloxera spots, was therefore little in evidence, and
was not considered a prominent factor in connection with the de-
struction of the vineyards.
The following facts were brought out. during the writers’ investi-
gations and have a direct bearing upon existing conditions in the
Santa Clara Valley at that time:
Extensive areas of a vineyard may be infested by phylloxera be-
fore characteristic spots are noticeable; a hghter crop and a slight
decline in vigor of growth are for some time the only apparent signs
of injury.
Infested vines change suddenly for the worse, becoming rapidly
stunted in growth, or even dying, when influenced by unusual con-
ditions either from lack or excess of moisture.
Injured roots, functioning poorly under normal conditions of
moisture, reproduce with difficulty fibrous roots, or feeders, to replace
those ihn have been destroyed by the insect, sine when subjected to
drought they starve the vine.
Brsessie e moisture, instead of benefiting injured roots, causes them
to rot and hastens the death of the vine.
For these reasons it is believed that the phylloxera was responsible
for a far greater share of the destruction of the Santa Clara Valley
vineyards than has been ascribed to it.
While Santa Clara and the southern counties have lost in acreage,
a larger gain has been made at about the same period and later
in other counties, especially those of Sutter, San Joaquin, and
Fresno. Many vines throughout the State have been killed by
phylloxera and not replanted; more have been grubbed out. and
replanted, sometimes more than once, and it is estimated that the
loss in these respects has been very considerable.
Mr. George C. Husmann, pomologist in charge of viticultural
investigations, Bureau of Plant Industry, United States Department
of Agriculture, estimates the loss at 75,000 acres; Prof. F. T. Bioletti,
of the viticultural department of the University of California, makes
a sumilar estimate; and Charles C. Wetmore, for many years identi-
fied with the board of State viticultural commissioners, considers
this estimate conservative.
VINEYARD DESTRUCTION.
PROGRESS OF THE DESTRUCTION OF A VINIFERA VINE.
According to conditions there is a great variation in the number
of months or years that elapse between its original infestation by
16 BULLETIN 903, U. S. DEPARTMENT OF AGRICULTURE.
phylloxera and the actual death of the vine. The following points
have important bearing on. this: .
Soil conditions and drainage—From a survey made throughout
the different districts of California, the following general statements
can be made in regard to the destruction of Vineyards when the vines
are 8 to 10 years of age or older before becoming infested:
Vines live longer in rich, deep, well-drained soils. Under such
conditions, vineyards known to have been infested for 20 years and
longer still bear crops, have only a few vines actually dead, and
but a small percentage bearing little or no crop.
Vines die sooner and the crop of the vineyard is more rapidly
diminished in quantity and quality when established on rich soil
only a few feet deep and wath poor drainage, or on side-hill soils
lacking moisture.
Vines are still more rapidly affected in heavy soils, more or less
shallow, with compact clay subsoil. In such types of soil, the vines,
more or less stunted and enfeebled. may hve a number of years.
After a winter of unusually heavy rainfall they may show a very
rapid serious decline or even a majority of them may die within a
year.
Vines growing in a well-drained, very loose, and friable sandy soil,
or one with a surface of blow sand several inches in depth, seem to
be almost immune to the attack of phylloxera.
As a sandy soil becomes heavier in texture and of poorer drainage,
so the vine succumbs more readily to the attack of the insect.
Age of vine at infestation.— Y oung vines are destroyed more readily
during the first three years, before they have established a fairly
good root system. When vines are § or 10 years old the quality and
texture of the soil become main factors, and the more or less rapid de-
struction of the vineyard depends on the adaptation of the vine to
the soil and the advantages of prolification and diffusion for the
insect. The general experience has been as follows:
Cuttings infested in their early growth rarely survive the first
year.
Rooted vines, infested from the time of planting, produce from the
start a very poor vineyard, which rarely lasts more than three or four
years, the individual infested vines living after infestation. hardly
more than two years. If vines become infested during the second
or third year from planting, they may last longer if they have
a good root system, and in this case the vineyard may produce one
or two crops smaller than normal and perhaps last five or six years.
When a vine is three years old or more before infestation, its longev-
ity depends somewhat on variety, much more on age, and especially
on soil conditions.
THE GRAPE PHYLLOXERA IN CALIFORNIA. 17
Too few American varieties, either nonresistant or resistant, are
grown in the State of California at this time to have been con-
sidered in this investigation.
Intrinsic vigor of vines —V ines of great intrinsic vigor always re-
sist phylloxera attack better than naturally weak plants.
Varieties of vines—Amongst vinifera varieties grown in Cali-
fornia, a few have shown certain resistance when inoculations have
taken “se: several years after planting. Such are, in order, Flame,
Tokay. Mission, and Muscat (Fresno district), and in a lesser degree
Grenache, Chasselas, and Burger. Laboratory tests with certain
- varieties in which phylloxera lesions rotted rapidly have shown that
Zinfandel, Thompson’s Seedless, Carignan, Burger, and Muscat suc-
cumbed more rapidly and Tokay and Grenache less rapidly.
Destruction of a highly susceptible vine—Under favorable con-
ditions for rapid phylloxeration, the hypothetical progress of de-
struction of a highly susceptible vine, as Zinfandel, with established
roots may be set down as follows: During summer and fall a few
larvee settle on a part of the root system; the following year in-
festation spreads to the surface fibrous and fleshy roots, and to a
certain extent to the large roots near the crown, and nodosities and
tuberosities are formed. ‘The third year the subterranean infesta-
tion spreads pretty well throughout the root system, although it
is rare to find year-old wood much attacked, for it appears that
the habit of roots of this age to slough the outer layer of bark pre-
vents the phylloxeree from retaining a hold, and compels those
already settled to move to other more hospitable portions of the root
system. In this year some of the larger roots decay under combina-
tion of phylloxera attack and excessive moisture in the subsoil or
become dried out from phylloxeration combined with too great
drought, and thus the flow of sap between the feeding rootlets and
the foal portion of the vine is more or less cut off. This results
in a shortening of cane growth and sometimes in an abnormally
large crop of grapes. During this third summer as the larger roots
die an emigration of young larvee takes place. Many winged forms
also may be developed. The fourth year finds the larger roots in
great part destroyed, the cane growth correspondingly reduced, and
a large number of fibrous and fleshy rootlets sent out from the
trunk just below the soil surface. The phylloxere colonize these
rootlets in spring, but leave them in summer, when they decay. There
is also a heavy migration from the decaying roots farther down
in the soil. In the autumn it is hard to find phylloxera on such a
vine, and this explains the maxim that the best type of phylloxerated
vine on which to look for the insect is not one badly stunted, but
rather one with slight stunting of the canes; in fact, one in the
1¢09°— 91 ==> |
18 BULLETIN 903, U. S. DEPARTMENT OF AGRICULTURE.
second or third year of phylloxeration. Such a vine as has been
portrayed generally dies in the fifth or sixth year from the initial
attack.
As has been pointed out above, the decline of a vine is influenced
by many conditions, and the hypothetical case given shows the mini-
mum longevity of an established susceptible vine after phylloxeration.
Under favorable conditions infested vines live much longer, and in
extreme cases their length of life seems hardly affected by the con-
tinued presence of the insect on their roots, a slight decrease in the
size of the crop being the only evidence of injury.
HOW THE PRESENCE OF PHYLLOXERA IS INDICATED.
The existence of the phylloxera in a vineyard is indicated by the
well-known areas or “oil spots,” so termed because of their man-
ner of spreading. A “spot” appears first in the form of one or
two vines showing a slight shortening of the canes and a premature
seasonal yellowing of the leaves, although the latter symptom may
be caused by the red spider (Yetranychus bimaculatus Harvey), or
by alkal in the soil. The year following this indication the vines
originally infested exhibit a more noticeably stunted appearance,
while other vines surrounding them show shght shortening of canes
and premature discoloration of foliage. After this the “spot” in-
creases in size, in course of time the vines in its center die, and
finally the vineyard may become totally destroyed. The writers have
never observed the “spots” to increase as rapidly in California as
they are reported to have done in the vineyards of France after the
time the insect first reached that country, when 2,500,000 acres were
destroyed in 25 years, and vineyards frequently have been observed
in California which had phylloxera “spots” of more than 20 years’
standing to have vines still living.
The “oil spot” generally is circular in shape, but sometimes it
assumes other forms. At times it is oval or narrowly elongate, the
latter form occurring on hillside vineyards through which water
rills run in the spring. In such cases spread of the “ spot” is often
rapid in a downward direction, indicating that running water is
an extra factor in the spread of infestation. The writers have
demonstrated by experiment (see “ Diffusion of phylloxera,” p. 100)
that the phylloxere can be carried in water from one vine to another,
and when the rains of March and April occur there are plenty of
active phylloxere on the roots. In other cases the spread of a “ spot”
follows the direction of the prevailing winds and it appears that this
spread is caused by wind agency in the transportation of wandering
larve in summer and autumn. In vineyards where vines are planted
rectangularly (1. e., 8 by 12 feet), instead of square, the infestation
THE GRAPE PHYLLOXERA IN CALIFORNIA. 19
very frequently spreads along the shorter 8-foot rows, indicating
that the insects traverse more easily the shorter than the longer dis-
tances. Aerial and subterranean migrations of wandering larvee
play an important part in the enlargement of phylloxera “ spots.”
Only an infinitesimal percentage of the thousands of wandering
larvee succeed in reaching their goal, but, as they are parthenogenetic
radicicoles, a single larva can cause a new infestation or start a
new “spot” at quite a distance from the original one, either in the
same or in another vineyard.
The estimation of root injury from external appearance usually
can be made with considerable accuracy, and the degree of infesta-
tion of a vineyard computed by the number of “spots,” their size,
and the stunted condition of the vines composing them.
The diagrams (figs. 2 and 3) indicate a phylloxera “ spot ” charted,
respectively, in the years 1914 and 1915. This “spot” occurred on a
heavy black clay soil on a hillside of moderate slope. It appeared
that the “spot” started about the year 1907 when the vines were 3
years old, and that the first vines died about 1911. Surveys of the
“spot” were made October 13, 1914, and November 5, 1915, and the
vines were designated in the following manner: Ten was given to
vines which showed no external evidences of phylloxeration; 9 to
those which showed very slight evidence, such as premature yellow-
ing of fohage and shght shortening of canes; 8 to those showing
more advanced symptoms of phylloxeration, and so on down to 1,
which was given to vines which showed only the most feeble vegeta-
tive growth. In order to portray the “spot” more vividly, symbols
have been utilized as follows: Healthy vines, //; vines designated 9
and 8, S; vines designated 7 and 6, 7; vines designated 5 and 4, U;
vines designated 3, 2, and 1, ); vines killed by phylloxera, solid dot.
In this vineyard every fourth vine had been replaced by a walnut tree,
and these places where vines have been pulled out and not replaced
are left blank in the diagrams.
In the diagrams not all the “spot ” is shown, for it has extensions,
the principal one being on the north side across a 24-foot avenue and
continuing down a swale for some 60 feet. Enough of the “spot”
is shown to indicate its general form. Between 1914 and 1915 there
occurred an unusually wet winter and the “spot” grew considerably
in the 12 months between the surveys. Although the number of dead
vines increased only from 43 to 49, and among the badly stunted
types not much increase was shown, there was a marked increase in
the number of vines showing recent phylloxeration.
When more than one variety of vine is included in a “spot,” a
good index of the resisting power of the several vinifera varieties
frequently is observable. Among the dead or moribund vines of
20 BULLETIN 903, U. S. DEPARTMENT OF AGRICULTURE.
the susceptible varieties stand out the more vigorous vines of the less
susceptible kinds or even individuals of the same variety.
HHHSSS SHH
HHSHSOS HHS HHH
SHHHHHS HHHHHH
S HSH SHH SHH H
SHHHS HHSSSOEHS SHH
The year previous to showing a marked decline, vines frequently
bear an unusually abundant crop of grapes, and stunted vines seem
to produce a larger amount of grapes in comparison to the size of
WSS SH SETTLES TAT Soe |
SHS SH HHH S5S2 EL SS SeSeti il aah |
H FLSA, FES ee TEU. 8 Bo, SIO TO 1
HHHS HSHS § S 8S Sh IS IST es
bd FI baS) S- SS. FL FL SEALS) SOT IS STL as SS
FL AD AAA SE ST SAS. S- STL OFS SESS Stat dE |
Re ae Oe
ISVALID AL IPS SS. OAL S SRS SLMAZS AILS TS fa ee |
BEE AHH SE. FOES SO LOD ALES SS ia |
HHH HSS FS SOD DDDO DISS Ss S
Ih igbizh Sahay Oe /@@®@ @ee DUS Stes
HHSHS SS TDOeGCOSOOOBOOUVUISSH HH.
HHSHSTDD@@*LD@O@DOIUVUISSH
HSS TSUV@ESOVEOESSBOBOQODVUUS SH
Sy 2S ER YL @D*® eee y heey Mean f H
HHSHSE SITIIT@D@ODOVUIS SHH
HhhHHS IIT. T1 COO OD, 1 LEO
HHHHHSE SS ITS LUD OLAS ES HAT
HHH HST a GED ELUE S Al Hl Af ;
it SATS TEE STE SOO LOT FT SES AS eh |
Fk:l1 Il HS S S'S 1T@OG OCU SSS 7A
SHHHHHS SEP II@IT SSHHHHA
IS: SoS oS UU Ss jg SOM ie
H/ HEALTHY SF) 7 ol a SS SHHHH
SP SWIGHT INFESTATION Mr Aap eee y WU Mepis Eee Ie!
f INMESTED SE SHHS HHH SH
OU OUNHEALTAY Ses: SSS |
D DyIne S) FSA FASE
@ Den Hl
Fic. 2.—Phylloxera ‘“‘ spot’ in Zinfandel vineyard, charted in 1914. (See text.) |
|
|
|
|
|
Bul. 903, U. S. Dent. of Agriculture. PLATE I.
Fig. 2.—Old vinifera vineyard infested throughout with Phylloxera and showing empty spaces
where vines have been killed; vine in foreground shows less infestation by Phylloxera than
others near by, and would be rated at 7, but the canes show obvious stunting.
THE GRAPE PHYLLOXERA IN CALIFORNIA.
- PLATE II.
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THE GRAPE PHYLLOXERA IN CALIFORNIA.
Phyllorera vitifoliae: Fig. 1—Phylloxera nodosities shown on Zinfandel grapevine:
a, Nodosities on terminal rootlets; b,nodosity showing Phylloxera feeding; c,adult louse;
d, molted skin ofsame. Fig. 2.—Phylloxera tuberosities on smaller root: a, Iniested
portion of root; 6, normal portion of root. Fig. 3.—Section of grapevine root showing
adult louse with eggsin situ. Fig. 4.—Sections of root infested: a, Newly formed tuber-
osity; 6, advanced stage of tuberosity; c, side view of older form of tuberosity; d, tuber-
osity causing the cracked concition of bark; e, young colony ofinsects as found on roots.
THE GRAPE PHYLLOXERA IN CALIFORNIA. | 21
their wood growth than do healthy ones. Such grapes mature, how-
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Fie. 3.—Phylloxera ‘‘ spot” in Zinfandel vineyard, charted in 1915. Same “ spot ”’
as shown in figure 2. (lor description see text.)
tent. Stunted vines produce leaves of a more uniform size than
healthy vines, and because the internodes of the canes are shorter,
the leaves appear more closely grouped, giving the “ cabbage-head ”
22 BULLETIN $03, U. S. DEPARTMENT OF AGRICULTURE.
appearance to the vines. Scarcity of rapid-growing terminal shoots
and absence of tendrils are characteristics of stunted vines. Plate
I, figure 1, shows a young vineyard which is uninfested and in which
the vines have made normal growth. Plate II shows a small phyl-
loxera “spot” in an old vineyard, the photograph showing stunted
vines in the foreground. Plate III and Plate I, figure 2, indicate
badly infested old vineyards, in which all the vines are phylloxe-
rated and most of them badly stunted. The vine in the foreground |
of Plate IIT is obviously stunted, although less so than its neighbors.
PHYLLOXERA ROOT LESIONS.
Root lesions are swellings on grape roots caused by the puncture
of the phylloxera beak. They are of two types, (1) nodosities and
(2) tuberosities. ;
The nodosity.—Nodosities (Pl. IV, fig. 1) are rapidly growing
swellings on the white fleshy feeding rootlets. They soon acquire
a characteristic greenish-yellow color, and curve and bulge around
the phylloxerz responsible for their inception so that the insects
come to lie in a depression (Pl. IV, fig. 1, 6). A nodosity may be-
come as much as six times the diameter of the normal size of the root
when several insects have settled upon it, and about twice the di-
ameter for a single occupant. Through its size, form, and color,
the nodosity is very conspicuous in comparison with the root and is
‘manifest proof of the presence of the phylloxera.
In most cases the formation of a nodosity arrests the growth of the
rootlet. At times the rootlet grows one-fourth inch or so in length,
and occasionally the puncture of the phylloxera does not affect the
rootlet in its growth, the subsequent swelling acquiring a lgnous
character and becoming a tuberosity. Nodosities are generally short-
lived, lasting about a month. Excess moisture hastens their decay,
lack of moisture dries them up, but a low, even temperature causes
them to last longer. :
The foregoing also applies to the American variety of vines styled
nonresistant. On the rootlets of the resistant American vines the
phylloxeree frequently fail to cause swellings, and when nodosities
are produced they are smaller, less fleshy, and brown in color. At
times, though no swelling occurs, the rootlet dies at the point of
puncture.
The tuberosity —Tuberosities (PI. IV, figs. 2, 4) also are swellings
caused by the puncture of the aphid. Though of a similar nature,
they differ from nodosities in form because of the lignous character
of older roots. They occur on all parts of the root system of vinifera
vines except at the apex of the growing fibrous rootlets. They may
ale a
THE GRAPE PHYLLOXERA IN CALIFORNIA. . 93
also occur on the trunk of the vine, both above and below the soil
surface. They are less commonly formed on roots of one year’s
growth than on older wood. On resistant vines tuberous swellings
are normally quite unusual, but they may be formed on the healing
growth of the cambium layer about an abrasion. On most American
vines of nonresistant type, tuberosities are abundantly formed. On
vinifera X resistant hybrids the more the resistant strain predominates
the scarcer are the tuberosities.
Tuberosities are formed at any time between March and October,
most abundantly during the summer months. They are formed more
readily on vigorous roots than on those somewhat dried or decayed.
Hibernants often choose tuberosities upon which to pass the winter,
besides inducing their growth at points as yet sound and uninfested,
the mere insertion of the beak being sufficient to stimulate growth.
Tuberosities vary considerably in their general appearance, even
on the same vine. Some are minute papille on the surface of
the root. Others are large, fleshy, rapidly growing, globular out-
growths, as much as half an inch in diameter, and this type is found
chiefly on the smaller roots. Others are enlargements of the girth
of the root at intervals, a type also confined to small roots. Others
consist of more or less uniformly rounded swellings of one-sixth
to one-fourth inch diameter on the root surface, and these are the
ones most commonly found on larger roots. Such tuberosities by
their growth generally split the epidermis of the root longitudinally,
and as the split tends to lengthen at both ends, the tuberosity assumes
an oval or elongate shape. Later, when the split enlarges, fresh
tuberosities are formed by aphids on the inner layer of bark exposed
by the split, and shortly a chain of lesions occurs along the crack.
These cracks lengthen and often involve a length of more than 6
inches. On roots growing horizontally or almost parallel to the soil
surface, the majority of the tuberosities will occur on the lower side,
the insects apparently settling there because of the greater moisture.
On vertical or sloping roots tuberosities occur more or less uniformly
all around. As long as they remain fresh, tuberosities provide an
excellent quality of food for the aphids. This condition should be
distinguished from the rapid development observed in the case of
aphids settled on root callus, which forms at the point of severance
and is caused by the action of the healing cells of the cambium layer
becoming greatly enlarged and very fleshy, furnishing excellent
food for the aphids, through the natural function of the wounded
root.
Many factors influence the length of existence of tuberosities. In
general, it is found that those formed in the autumn will last until
the rainy season, and commence to decay immediately afterwards.
24 BULLETIN 903, U. S. DEPARTMENT OF AGRICULTURE.
Their decay is expedited by a heavy rainfall and a high-water table.
Those formed during the spring and summer in a moist environment
rarely persist fresh beyond two months, and most of them decay
about ‘one month after they arise. It has been repeatedly observed
how quickly a fresh tuberosity decays when it is placed against wet
sand, and if a stream of water finds its way down a root the tuberosi-
ties thereon start to decay immediately. On the other hand, they
are more capable of withstanding dry soil conditions than are the
nodosities, and under conditions approaching drought, which some-
times occur in late summer and autumn, may last for a considerable
time and even lignify, the dry environment having caused the insects
settled on them to seek more favorable conditions of moisture and
at the same time having kept in check decomposition. Tuberosities
withstand a considerably greater range in temperature than do
nodosities, and they are not affected by sudden changes in tempera-
ture in the same manner as are the nodosities.
Tuberosities grow larger and more rapidly in proportion to the
soundness of the roots. On roots previously uninfested the growth
of the swellings is rapid and vigorous, and a root, after it has been
heavily phylloxerated for several months, becomes so greatly ex-
hausted that it can not respond to the punctures of the aphids by
developing new swellings, and the phylloxere that are not gradually
driven away to seek more nutritious food develop on the root without
causing swellings. The decay of the tuberosities begins at the place
first punctured by the aphids, generally at about the center of the
swellings. The tuberosity forms around the insect, and decay is
first evident as a small, blackened spot, sometimes exuding a liquid.
The rapidity of decay of tuberosities is in proportion to the increasing
moisture content of their environment, and in an unusually dry
environment they frequently will lignify without causing the tissues
to rot. Under moist conditions the inflated cells rapidly break down
and decay usually spreads, and fungi and molds enter the tissues, es-
pecially in the case of large bulbous swellings. Decay finally drives
off the aphids, but through their stimulating action they are often
able to retain the freshness of a tuberosity for some time after it
has been surrounded by decayed tissues, and occasionally a fresh,
vigorous specimen is found on a root otherwise quite decayed. The
nutritious quality of these tuberous lesions provides for the produc-
tion of nymphs in great numbers.
HOW ROOT LESIONS AFFECT THE HEALTH OF VINES.
Tt has been shown in the foregoing pages that the nodosities are
those phylloxera lesions formed at the apex of growing fibrous root-
lets, whereas the tuberosities are lesions formed on all other parts |
eee er eee eee a
THE GRAPE PHYLLOXERA IN CALIFORNIA. 95
of the root system. Since the vine derives its plant food through
the growing rootlets that thrust their way through the soil, it is
obvious that when such rootlets rot as a result of the decay of the —
nodosities situated on them no more sustenance can be afforded
the plant through this medium. If, on the other hand, the rootlets
continue to grow notwithstanding the nodosities situated on them,
and if the nodosities lignify, the supply of nourishment provided by
the rootlets is not cut off, and the nodosities become in effect tuber-
osities. This is often the case with resistant vines, and much more
rarely with vinifera or nonresistant Americans. In resistants these
tuberosities generally lignify and heal, but in the other types of vines
they do this only if their environment is quite dry. Nodosities effec-
tively destroy the terminal rootlets; but since the insects spread
very slowly on resistants, a vine of any vigor has abundant feeders,
and thus it follows that resistant vines bearing very few or no tuber-
osities, but having many nodosities, do not succumb to phylloxera.
Resistant vines never lack the power to produce enough feeding
rootlets to sustain them as long as the following conditions, which
are normal to these vines, obtain: (1) When the development and
spread of the phylloxere on them are comparatively slow; (2) when
a large percentage of insects that have been raised on the nodosi-
ties become nymphs and later leave the roots as winged migrants,
in an endeavor to reach the surface of the ground or the aerial
parts of the vines. Both of these conditions may be affected by the
quality of plant food, as will be shown. Instances have been seen
in which young resistant vines have been rid of their entire infesta-
tion because all of the immature phylloxeree became winged migrants
in the autumn, but in the majority of cases of infested resistant
vines under observation there remained in late fall a small wingless
infestation, and in some instances where the vines had been growing
in small pots with insufficient nourishment infestations of wingless
aphids persisted, and the production of winged migrants during the
autumn was proportionately small. These wingless infestations,
however, were not prolific. It appears that thrifty resistant vines
afford poor nourishment for phylloxere, and they do not respond to
phylloxeric irritation by producing swellings. When, however, re-
sistant vines become weakened through a poor supply of plant food,
the phylloxerz attacking them persist and the vines respond to the
phylloxeric irritation and form lesions.
Although the decay of the nodosities on vinifera vines destroys the
feeding rootlets, this in itself is not a potent factor in the destruc-
tion of the vines by phylloxera. Except under abnormal conditions,
such as the confinement of vines in pots with impoverished soil, no
case has ever been observed in which the death of a vine could be
attributed solely to the decay of nodosities, whereas instances have
26 BULLETIN 903, U. S. DEPARTMENT OF AGRICULTURE.
been observed wherein vines flourished with their vitality but
slightly impaired, notwithstanding a nodositous infestation extend-
ing over several years. One such instance was that of a 20-year-old
vineyard of Burger and Chasselas (vinifere) near Napa, Calif.
In 19138 the vines had been phylloxerated for upward of eight years,
and each year the nodosities had been extremely abundant and prac-
tically no tuberosities had been developed, yet the vines appeared
quite thrifty, owing to the maintenance of a sufficient number
of uninfested feeders. It is the decay of the tuberosities on the
larger roots, which the vine can not replace, that causes at first the
impairment of the vine’s functions and later results in its death.
The simultaneous decay of many tuberosities is the cause of rapid
decline in the vigor of a vine and is the prelude to the vine’s death.
The larger roots near the crown of the vine are especially susceptible .
to tuberositous decay, while the decay of a root below the crown
is often very slow. This lower portion under favorable conditions
is able to maintain itself undecayed for months, if not years, and is
capable of providing nourishment for phylloxere. It is frequently
observable that vines retain their vigor despite a ring of decay at
the crown of the roots, and do not become stunted until the major
portions of the larger roots have rotted.
In a discussion of the effect of root lesions on the health of vines,
emphasis should be placed upon the decay of the tuberositous le-
sions and upon the fact that this decay is invariably hastened by
moisture and retarded by dryness. Decomposition is often hastened
by the work of fungi, molds, thysanurans, and tyroglyphid mites.
The most common mite so working is ?hizoglyphus elongatus Banks,
specimens of which were determined by Mr. Nathan Banks. It is
a rather large species and is very prevalent throughout the grape
sections of California. It was frequently reared on decaying roots:
kept in the cellar of the laboratory. The mite is hyaline white,
with two brown circular spots, one behind the other, on the dorsum
of the abdomen. |
NOMENCLATURE AND SYNONYMY OF THE GRAPE PHYLLOXERA.
The genus Phylloxera was erected in 1834 by Boyer de Fons-
colombe (10). The type species is P. quercus de Fonscolombe. In
1856 Asa Fitch (9) described the grape-leaf gall louse as Pemphigus
vitifoliae. ‘The species was obviously placed in the wrong genus.
In 1867 Shimer (21) erected a new family (Dactylosphaeridae) and
a new genus, Dactylosphaera, for a new species of his (globosum) and
tentatively placed vitifoliae Fitch in this new family and genus. Ina
footnote he also proposed the genus Viteus for Fitch’sinsect. In 1868
Planchon (20) described the grape root louse from France as Rhyz-
THE GRAPE PHYLLOXERA IN CALIFORNIA. Dit.
aphis vastatrix Planchon, and in the same year Signoret (22) placed
the species vastatriv in the genus Phylloxera de Fonscolombe. ‘The
year following Westwood (23), in England, described the insect as
Peritymbia vitisana, but in a later article the same year he placed |
his species in synonymy as follows: Peritymbia vitisana Westwood=
Pemphiqus vitifoliae Fitch, Dactylosphaera (?) vitifoliae Shimer,
and Phylloxera vastatrix Planchon (19). Until 1900 the name gen-
erally recognized by writers had been Phyllowera vastatrix Planchon.
In 1900 Del Guercio (12), in Italy, erected the genus Xerampelus to
receive the grapevine species, which he therefore called Xerampelus
wvastator. This genus has not been recognized by all later authors.
Grassi (11, p. 12) would retain Shimer’s proposed genus Viteus as a
subgenus to Phylloxera, and would thus name the species Phyllowera
(Viteus) vastatrix. The present writers are inclined to retain the
specific name vitifoliae Fitch on account of its evident priority over
Planchon’s more widely known vastatrix, and notwithstanding the
objections raised by authors as to its orthographical correctness
(witisfolii and vitifolit have been preferred and written). As to the
generic title, it has been decided that Phylloxera will be retained,
the question of the subdivision of the genus being left to those who
have had more opportunity to study the specific ramifications of
this group.
The synonymy of the grape phylloxera as understood by the
writers is therefore as follows:
Phylloxera vitifoliae (Fitch).
Pemphigus vitifoliae Fitch, 1855-56.
Dactylosphaera (?) vitifoliae (Kitch) Shimer, 1867.
Viteus vitifoliae (Fitch) Shimer, 1867.
Rhyzaphis vastatriz Planchon, 1868.
Phylloxera vastatriz (Planchon) Signoret, 1868.
Peritymbia vitisana Westwood, 1869.
Xerampelus vastator (Planchon) Del Guercio, 1900.
Viteus vastator (Planchon) Grassi et al, 1912.
BIOLOGY OF THE GRAPE PHYLLOXERA IN CALIFORNIA.
THE LIFE CYCLE.
The complete life cycle of the grape Phylloxera under natural con-
ditions, i. e., on the wild vines of eastern North America, is extremely
complicated (fig. 4). It is not the intention of the authors to enter
into all the ramifications of this cycle in the present paper, but it
may be said that the following are the main forms that occur: (1)
The stem mother or fundatrix, which hatches in spring from the
winter egg, ascends to an early leaf, settles on the upper surface,
and causes to form around her a pocketlike gall opening on the
28 BULLETIN 903, U. S. DEPARTMENT OF AGRICULTURE.
BELOW GROUND | ABOVE GROUND
Fic. 4.—Phylloxera vitifoliae: Genealogical graph of the grape phylloxera in the eastern
part of North America and in the Mediterranean regions. A, Hibernant radicicole;
B-G, successive radicicole generations; H, winged sexuparous migrant; J, sexes;
J, stem-mother gallicole ; K—P, successive gallicole generations, part of the young larve
of which proceed below ground (Q) to join the radicicole circle at various stages de-
pendent upon the gallicole generation of which they were members; Z, emergence above
ground of the wandering radicicole larve. In this figure, in order to avoid undue con-
fusion, no account has been taken of the development in the galls of winged sexuparous
migrants. Such development is unusual, but it indicates the possibility of a life cycle
entirely aerial.
THE GRAPE PHYLLOXERA IN CALIFORNIA. 29
upper side of the leaf; (2) several parthenogenetic generations to
which the stem mother gives rise, some of which settle on the foliage
and produce new galls, as snl ealles, while others repair to the roots
and settle on them as -aighokealiess (3) parthenogenetic generations
on the roots descended from the inelllemis which went from the
foliage to the roots; (4) winged migratory forms, comprising a very
variable percentage of the root and gall forms, eadece dy in summer
and autumn, slits fly or are Penenaricd by wind to other vines and
oviposit eines under the bark or on the leaves; (5) the true sexes,
which are wingless and beakless; (6) the winter egg, deposited made
the bark by the sexed female ofteen coition; (7) radicicoles, born on
roots in the late autumn, which pass the winter thereon as small
hibernants, mature the spring following, and give rise to radicicole
generations which succeed one another during the summer and
autumn. ‘This, briefly, is the life cycle that occurs in parts of
Europe where American vines are used for stock, and in the eastern
and southern United States on the wild grapes and on varieties de-
rived from them.
It will be observed that the winter may be passed in two forms—
the winter egg and the hibernant, the former on the aerial and the
latter on the subterranean or root portion of the vine. On certain
wild grapes, as V2tis riparia, V. rupestris, and V. berlandieri, and on
hybrids from these species, the former is the normal form, and hiber-
nating larve are rare. On species like Vitis labrusca, V. monticola,
and their derivatives, both forms may occur. On hiics (Vitis
vinifera) the latter form is by far the more common. In the
majority of European grape districts both forms occur, the former
on American resistant vines and the latter on vinifere, but in other
localities, even where resistant vines are used, the winter egg is very
scarce. These include certain regions of France and California, and
it appears that in California the hibernant is normally the only form
that passes the winter.
The suppression of the winter egg, and, therefore, of the succeeding
gall form, brings about a modified hfe arate in aie California vine-
yard which may be briefly described as follows: (1) The hibernant
radicicole passes the winter as a larva on the roots and occasionally
on the trunk beneath the bark. (2) The hibernant, when mature,
gives rise to generations of radicicoles, and the aphids that issue
from eggs in late autumn become hibernants. (38) A certain per-
centage of radicicoles, varying from causes such as humidity, tem-
perature, condition of food, and variety of vine, develop into winged
migrants and issue from the ground. (4) Radicicole larve forsake
the roots and seek to reach other vines either by way of the soil
surface or through subterranean passages such as cracks.
30 BULLETIN, 903, U. S. DEPARTMENT OF AGRICULTURE.
The part of the life cycle from the sexes to the gallicoles through
the winter egg and fundatrix is either omitted or does not proceed
beyond the winter egg in California, notwithstanding the frequent
ABOVE GROUND
BSELOW GROUND
Fie. 5.—Phyllorera vitifoliae: Genealogical graph of the grape phylloxera in California.
A, hibernant radicicole; B—G, successive radicicole generations; H, winged sexuparous
migrant; J, sexes; Z, emergence above ground of the wandering radicicole larve.
abundance of resistant types of vines, types many of which normally
bear galls in other localities. The résult is that the California cycle
(fig. 5) is purely parthenogenetic and is therefore greatly modified
from the original cycle (fig. 4) occurring on wild vines, the natural
hosts of the insect.
THE GRAPE PHYULLOXERA IN CALIFORNIA. Sl
RESUME OF LIFE HISTORY IN CALIFORNIA.
A résumé of the life history will be presented before all the dif-
ferent stages and habits of the phylloxera in California are discussed
in detail. This résumé is confined to the biology of the insect on
viniferze and does not consider the life history on resistant roots.
Over 99 per cent of the phylloxere pass the winter as small brown-
ish unmolted larve, the remainder hibernating after having passed
one or two molts. All parts of the root system are used for hibernat-
ing quarters, but the majority cluster on the larger roots, following
an upward migration in the fall.
Coincident with the first sap flow in early spring is the growth of
the hibernants, but in a given vineyard the earliest individuals com-
mence to grow fully six weeks before the most tardy ones, so that
after the foliage has opened, hibernating larvee are still to be found
on the roots. The development of the hibernants is considerably
slower than that of the summer broods, and the former mature on
the average about five and one-half weeks after they commence their
spring growth. The development of the larvee is at all times influ-
enced by the quality of food and by conditions of humidity and
temperature.
Upon casting its fourth skin, the hibernant is mature and com-
mences ege deposition. Its progeny are the first-generation phyl-
loxeree, and these on hatching from the eggs either settle beside the
egoshell or go in search of new food. Many aphids settle on young
growing rootlets and produce the fleshy swellings, termed “ nodo-
sities.” Others settle upon older roots and produce swellings, termed
“tuberosities.” Still others develop on roots without causing the -
development of either perceptible swellings or lesions. Individuals
feeding upon nodosities develop more rapidly than do those on the
unswolien surface of the root. The nodosities usually decay within
a few weeks after their formation, and in most cases the destruction
of the rootlets follows. The tuberosities also usually decay in time.
The rotting of the nodosities is not very serious, as the vine can
supply new apical growth, but the decay of the tuberosities leads to
the decay of the larger roots either wholly or in part, and as a result
the vitality of the vine is greatly impaired, or the vine is killed
outright.
The first-generation individuals are mature in from four to seven
weeks after the eggs have been deposited, and they in their turn
deposit eggs, which produce further generations throughout the
summer and autumn.
Owing to the fact that, under favorable conditions, the adults
deposit eggs during an average period of 45 days, an overlapping of
generations ensues during the summer and fall. In order to avoid
32 BULLETIN 903, U. S. DEPARTMENT OF AGRICULTURE.
confusion, it is assumed that there are five generations annually,
since this number is about the average in a vineyard in which the
sap moves early, although there might be, under certain conditions,
from one to eight or even nine generations within a single year.
The hibernant generation having matured in April, the succeeding
generation matures about the time the canes have ended their first
rapid growth, approximately the end of May. Succeeding genera-
tions mature on about the following average dates: Second, July 6;
third, August 15; fourth, September 30; the fifth generation hiber-
nating.
A variable percentage of the larve of generations 2, 3, and 4
becomes nymphs, and these later emerge from the ground as winged
insects and either fly away or are borne off on the wind. Large
numbers of these are caught in spider webs. Many of the newly
hatched larve develop a wandering tendency just after they have
issued from the eggshell and seek to emigrate to other vines either
through the soil or:over the surface of the ground. Large numbers
of these migrating larve are also caught in spider webs on the surface,
~and while only a small percentage reach their destination, a single —
individual may start a new infestation. Those of the larve that suc- -
ceed in fastening upon a root or rootlet develop as radicicoles.
The winged forms normally occur from June to October, and the
wandering larve are found from July to September.
During July and August, when the adult radicicoles are most
prolific, incubation and development proceed most rapidly, and the
phylloxera may be said then to have reached its most active stage.
It is at this stage that the greatest damage is done to the roots of the
- vines, although the effects are not generally apparent until the fall
and winter following, when the lesions formed during the summer
have decayed. !
At the end of September a few of the newly hatched larve
hibernate, and throughout October successive generations become
hibernants, so that by the end of the month a large majority of the
phylloxera have reached this stage. During November and the
first half of December, a few mature radicicoles and growing larvee
may be found, but after the middle of December, it is unusual to
find any form but the hibernating larva.
Under conditions of abundant food supply, the period of egg
deposition of the radicicoles averages 45 days and may reach a
maximum of 110 days. This average is nearly constant throughout
the season. The average number of eggs deposited is about 117,
but under certain conditions the number may be increased to 486.
The daily average number is about 24+ eggs, and as many as 23
eggs have been deposited in 24 hours by a single phylloxera.
THE GRAPE PHYLLOXERA IN CALIFORNIA. 38)
The rate of egg deposition is usually indicated by a sharp rise shortly
after commencement, followed by a gradual decline. During the
period of egg laying the adult feeds, and after the last ege is laid
may live for as loner as three weeks.
Incubation mtnere ls is influenced by temperature, and the dura-
tion of the incubation period may vary from five days in July to
over a month in December. Very few eggs are laid in December, but
in March and April, when many eggs are deposited, the maximum
period of incubation is 27 days.
The larve mature in midsummer in about 15 days, and in sel
and November in about 34 days, and the hibernant generation de-
velops in about 180 days. The winged forms mature more slowly
than do the wingless individuals, since the fourth or nymphal instar
is noticeably extended beyond that of the corresponding wingless
stage.
In the late fall a few individuals intermediate in structure be-
tween the nymphs and radicicoles are found. ‘These are called
“nymphicals ” or intermediates and, so far as is known, they de-
posit the same type of eggs as the radicicoles, although they are
not prolific. From egg deposition to the molting of the final skin,
the period covered by the sexes, which develop from eggs of two
sizes laid by the winged forms, was about 12 days in confinement.
All stages of the phylloxera molt four times, and the first instar
is always the longest (the adult instar excepted).
HIBERNATION.
The phenomenon of hibernation—Throughout autumn and early
winter an ever-increasing percentage of newly hatched radicicole lar- _
vee, instead of increasing in size and maturing normally, remain
as very small brown phylloxere (Pl. LX, d, p. 64). As winter pro-
gresses, the mature individuals die, leaving only the small brown
larve and a few unhatched eggs. As soon as these late eggs hatch,
the larve settle down, becoming brown like the others. These small
larve are the hibernants, and as such they remain throughout the
dormant period. Occasionally phylloxere that have passed one or
two molts hibernate. This type is quite unusual, and probably con-
sists of individuals that have reached a certain stage of development
and are unable, through lack of nourishment, to mature, most of them
dying before spring.
Hibernant larve occur on all kinds of vines—on vinifere and
on American varieties and hybrids. While this form of phylloxera
occurs more or less sparingly on American resistant vines (Vitis
riparia, V. rupestris, V. berlandieri, etc.) and on some American
1900°—21——3
o4 BULLETIN $03, U. S. DEPARTMENT OF AGRICULTURE.
nonresistant resistant hybrids, it finds its greatest development
on viniferee and on certain American nonresistant varieties of Vitis
labrusca, V. aestivalis, and V. monticola. On the wild species of
Vitis of the eastern and southern parts of North America, consid-
ered as the original hosts of the grape phylloxera, is found a com-
plicated life cycle embracing gallicoles (gall lice), radicicoles (root
lice), winged migrants, sexed forms, winter eggs, and true stem
mothers. The hibernants are rarely abundant on these wild spe-
cies of vines, and the winter is passed chiefly in the winter-egg
stage. On vinifera (Vitis vinifera) this complicated life cycle is
rarely completed, and a simpler one, comprising only the root forms,
obtains. Therefore, in the absence of the winter egg, the winter
period must be tided over by another form, which is supplied in
the hibernant larva. It appears that, to the phylloxera, V2tis vinifera
is an acquired food plant, and that the nature and construction of
the Old World grapevine has changed the habits and life history
of the grape phylloxera feeding on it.
On viniferz, although hibernation takes place chiefly on the
larger roots and on the subterranean portion of the trunk, it occurs
also on nodosities and on smaller roots.
Hibernants are located both on lesions and on the normal surface
of the roots. On the varieties of resistant vines and certain hybrids
(vinifera X resistant and resistant American nonresistant) that
have been examined, it has been found that hibernation occurs
chiefly on nodosities and less frequently on the norma! root surface.
Tuberosities rarely are formed on these vines. On American non-
resistant and vinifera X nonresistant hybrids, hibernation was
chiefly of the type found on the vinifere. On Golden Champion,
Agawam, Catawba, Isabella, Lenoir, and Delaware, hibernants oc-
curred on tuberosities, nodosities, and the normal root surface. On
Moore’s Early they were located on nodosities and on larger roots
but not on tuberosities.
Appearance of hibernants.—The hibernants (PL TX eds es
p. 64) appear as little oval brown insects flatly aed to the
surface of the root, their legs folded underneath the body. The
antenne are borne at right angles to the major body axis, and hardly
project beyond the maximum width of the body. The whole insect
generally shows one color, but sometimes there is a darker median
longitudinal line, except on the head. In those individuals which
have molted before going into hibernation, a similar shade of darker
brown occurs. Occasionally lighter individuals will be noted, but
none is ever as pale as the growing and feeding radicicole larve.
Hibernants located under several layers of bark, as a rule, exhibit a
paler color than those living more exposed.
THE GRAPE PHYLLOXERA IN CALIFORNIA. 35
FIXATION OF BEAK.
To secure information regarding the fixation of the beak in the
root five lots of hibernants were examined on January 23, 1914.
The results are given below.
TABLE II.—Fixation of beak of hibernants of the grape phylloxera,
Number | Number
Number , :
Lot No. of indi- ee ia Remarks.
viduals. | fixed. free.
a3 Bee a Saabs 25 12 13 | Under 2 layers of bark on large root.
DA ERE Haat oe 25 24 1 | Large root; insects originally under 2 layers of bark,
but layers peeled off Some time before experiment.
Be ae Pees tte, CEE 25 16 9 | Small root; insects on tuberosities.
fe Sh SG Be 25 22 3 Do.
Bid aes keder. Sopa eer 20 8 12 | Under several layers of bark on stock of vine 3 inches
below soil surface.
Totaleeaanas- 120 82 38 |
In lots 1, 2, and 5 the individuals that had their beaks fixed in the
roots were obviously the more healthy. In lots 3 and 4 all the
phylloxeree appeared equally healthy. They were on more succulent
roots than those in lots 1, 2, and 5, and it may be that on such succu-
lent food the hibernants have a habit of driving in and drawing out
their beaks at will, whereas on harder roots this would not be pos-
sible. It is evident that hibernants situated on the outside bark of a
root are likely to be washed off by water if their beaks are not in-
serted into the root. The experiment would serve to indicate that in
the individuals of lots 1 and 5, wherein the hibernants were protected
under layers of bark, the majority had their beaks free, while in lots
2, 3, and 4, wherein the hibernants were exposed, the majority had
their beaks inserted, so that it appears that the fixation of the beak
acts as an anchorage.
NOURISHMENT.
The hibernant larva partakes of nourishment very slightly, if at
all, before it settles for the winter. During the period of true
hibernation it apparently takes no nourishment. Therefore it is
probable that the great majority of the hibernants take their first
food when they arouse themselves from their lethargy in spring. Of
those observed to feed before hibernating, a few pass one or rarely
two molts, while the rest remain unmolted but larger in size than the
true hibernating larva. The writers have observed instances in
which severed pieces of roots infested by hibernants formed winter
lesions, the presence of the beaks in the root affording a stimulus.
36 BULLETIN 903, U. S. DEPARTMENT OF AGRICULTURE.
Hibernants on nodosities sometimes keep these fresh until spring
by the stimulating action of their implanted beaks. Such nodosities,
especially in vinifera and labrusca vines, otherwise usually fail to
pass the winter in a fresh condition, as they are susceptible to rot
through moisture.
DURATION OF INSTAR.
With the exception of the winter egg, the nibernant instar is the
longest found in the life cycle of the phylloxera. dos: 22 68
21 |.-.do-..-| June 19 11 | July 13 24 35 69
PA\| Vee Ce ameses Rae (0 eee EE eedote 24 35 _ 69
FES | SGT --| June 20 12 | July 15 25 | 37 69
24 |...do ---| June 17 9} July 7 20 29 68
25a GOs |=- 20 O5=,5- 9| July 8 21 30 68
26 |.--do..-.-| June 18 10 | July 2 14 24 68
Pe GOR (ye | Rees Co eee 10; )2=-dos- 14 24 68
Par eX eoeiewee| Pike 0 U8 pari t 105) dose 14 24 68
295 edo. =|. -2do: 10 | July 4 16 26 68
305|==dol==-|=--do: - - 10 | July 6 18 28 68
51 EiG Gene Mee Cement ION des 18 28 68
Soe Mages. =| =- doles 2 107) des 18 28 68
Sd i)5-200-- 32) -.-00... 2 10 | July 7 19 29 68
oe) S22dos-=-|>--00- > 2 10) |2=do== 19 29 68
35 | May 25 | June 4 10 | June 19 15 25 67
36) |: Sdoere-|/ do_5. 10 | June 21 17 27 67
37 |..-do |} June 5 11 | June 23 18 29 67
38 fi hidos © 2|i2-do: 11 | June 24 19 0 67
39 |...do....| June 6 12 } June 25 19 31 67
40) 2dor= = =|--2d0-4-- 12 |...do 19 31 67
Ate dO | 5 dO= 5-7 12 | June 27 21 33 67
DAN EM AG Cree pees Ca eee 12 |...do 21 33 67
43) dos. =| do: - + 12 | June 29 23 35 68
44 |...do...-| June 8 14| July 2 24 38 68
7 Gp) ees Veen eae CS 14 | July 3 25 39 68
THE GRAPE PHYLLOXERA IN CALIFORNIA. 61
Taste XIII.—IJncubation and development of radicicole of the grape phylloxera
on living vines, Walnut Creek, Calif., 1913-1915—Continued.
SECOND GENERATION, 1913.
Total
Indi- Incuba- Date . : te F Average
: Date egg | Date egg A F Growing | period of] Variety of vine and a
yoo deposited.| hatched. saat pnsec at period. geveln number of cage. peel
Days Days ele
1 | June 10 | June 20 10 | July 8 18 68
2 | June 11 | June 19 8) fee dos- 19 68
3 | June 12 |..-do- U NosaCl@se 19 68
ADB d ose June 20 8 | July 11 21 69
5 | June 30] July 6 6 | July 20 14 70
Gul Seed One July 8 8 | July 22 14 70
CNeccCOs5.c.4|boStc5 c 8 | July 23 15 70
SV eect ooe Galle caloe SF |e--dos- 15 70
OF ed ostee |e dose 8 | July 31 23 71
10s \2--d0=52-) duly (9 9 | July 24 15 70
1 ee dokeeeleee GOs 9 | July 25 16 70
19} WeBeOKOsc.culloce doses: 9} July 31 22 71
13 | July 1 doze 8 | Aug. 4 26 71
145 |e dorecelsze doles 8 | Aug. 7 29 71
15 ped Ossee aac dona 8 | Aug. 11 33 71
16 | June 30 |..-.do:- : .|) 9| Aug. 8 30 ql
17 | June 26 | July 3 7 | July 21 18 25) |p DULLED Wiles jtecie cn eiee 70
185 |5-=d0s., 24] July, <4 8 | July 25 21 Pe) Nooaee CERES eres meee A Ree 70
19 |...do. ew do-5 8 | July 26 22 0) los5oe Cosas ieee cee 70
20 |...do. do.. 8 do 22 9) |S o5ac GOBER eae es aenee 70
OAT ecko (loos Or Soe do... 8 | July 28 24 B94! enous GOs Rages eee 70
2202 22dOse July 5 9 | July 29 24 o) lloaoae COs ease eee 70
OB NAO ons alloceOWaoe 5 9} July 31 26 By) sees GOS 2 eae ae ey Sa 70
124} June 27| July 4 7 | July 28 24 at ous ae GOs Saas 70
25 do.. July 5 8 | July 31 26 Yan |e OER eee eee 70
26 | June 30 |..-do.. 6 | Aug. 8 23 29) BuUreelVieteecaecee tee 71
Ta |aee Ose July 6 6 | Aug. 10 35 ANS eee One eas sty 71
W28eleeed Ore July 7 7 | Aug. 12 36 AS) tec: GOs ett eeee ae eee val
OA NEKO 5 5 pallooat War 7 do 36 AS Ae. Oe n ae eee 71
130 | July 1]|July 8 7 do 35 AD eerste GOs ee ete eee 71
315 |se2d Os Eadoe- 7 | Aug. 13 36 CO Bic GOS Mine es eye 71
132) |PUULYs 2a |eee GO 6 | Aug. 14 37 ADT avaere GOs none a ee 71
UBB ecco call diblhy) al@) 8} Aug. 18 39 A a8s2 Gomes eens es See ral
THIRD GENERATION, 1913.
1} July 23] July 31 8 | Aug. 25 25 33 | Thompson’s Seedless I. . 71
2] July 28 |] Aug. 5 8 | Aug. 28 23 Sil |) WHORE GGoccéeconquer 71
3 | July 29] Aug. 7 9 | Aug. 30 23 BY) lnacoe GODS a ee 71
AN ediens alloca ln- 9 | Sept. 1 25 SAN ee ss GOR 2s Sanaa eee 71
BS Hoa Ke Aug. 8 10 | Sept. 3 26 aX8 eooos COtisc nis Nae ee 71
FOURTH GENERATION, 1913-14.
appar 6 dial ei pt h Thompson’s Seedless I. - 3 71
. 18 10 I || Chae waay oyna ICO eS Oosawa ee 70
5 oP d
30
6
9
4 |
6
7 |
10: | ee joeaa leas (CKO SAN ee Sear May 20 |
1D | ee eee ee GOP seca ae Apr. 15 | 203i beeen tae ee es GOS ee eR BEEN eRe Ala eterno
TH fee Sener 2oi|eiete ge: Apr. 24 | Diets eer akon ing ee: GOS ae ny payers (ist Sent
De AN nee cl (la Osa a aie eee Apr. 28 | CAG sree ee ATL RG C0 Ea ae 5 oles FES re. Po ae oe
FIFTH GENERATION, 1914.
1| Apr. 25| May 9 14] May 28 19 335) PMUUISCa Teles eee ate 62
2a Are 26h es eGOree= 13 GOze- 19 S2ileenee GOce as? oars ee ices 62
3 Gosecee eed Oresee 13 | June 2 24 STA aa GIO abe ed See ae 63
4} Apr. 27 do=.-.- 12} June 1 23 Bolle GOmee ay eee cases: 63
5 0-2 ed Oseeee 12} June 2 24 AD Wadsac ORG eget Rice ee ea 63
6 Apr. 28 }..-do...-- 11 CWccue 24 35) Peer COE eee oe seis 63
al |e GL Ose (O1)=cooe 11} June 3 25 aD |lsoued Oks Se 5esa6hoor senses 63
iIndicates winged migrants. ? Hibernant. 3 Indicates average temperature of incubation period alone.
62 BULLETIN 903, U. S. DEPARTMENT OF AGRICULTURE.
TasLe XITI.—IJncubation and development of radicicole of the grape phyllorera
on living vines, Walnut Creek, Calif., 1913—1915—Continued.
SIXTH GENERATION, 1914.
: 3 ty Toial
Indi- Date Date | Tneuba- Date Growing | period of] Variety of vine and aes
vidual] egg de- ezg tion insect SSS Sy SSs ararnere temper-
No. | posited. hatched. | period. |maiured.| +* ; Sete | TR eee | ature.
| j é
| OT | J HT
| Days. | | Days Days one
1| May 29] June 7| 9] June 24 | 17 | 26 | Muscat TXA....__..-._. 67
2) June 2)Tune 8 6| July -1) 23 | 29} Grenache TIA .____._____ 68
3/| June 9] June 19 10 | July 10 2] | a4 Miscat EXAL 7k Tek 69
4 ---do Bate June 20} 11 | July 26 36 | =i fl year dos 228 be Se Ge 69
|
SEVENTH GENERATION, 1914
1] June 24] July 3 9| July 23 | 20 | 29 | Muscat IXA_........... 70
PH ee Teel July 4 10 | July 29 25 | = Ty Bees dpizs nae eS Aes 71
3| June 25} July 3 8} July 23 20 | 7) eee dos. tet =a 70
Ao. = July 4| 9] July 30 26 = yy ee dase Sees 7
5 | Some 26 |__-do__.-- 8] July 28 24 32) sases do... 0 = Sc ee 71
oy) se mee (ae [eee 8 | July 30 26 S| eee dp. ete 8 eet 71
7| July 1|July 9} 8| July 29 20 | 28 | Grenache ITA ____.._._. 72
8| July 2] July 1 9|.. dos =! 18 | 7 6 Meee Bi: Ais Sas 72
9 27 Pres fees 7 ee 9} Aug. 1 21 | =) Ey eee 8 ae ee oe EE 7
10) Snly So? | § | Aug. 3 23 | = Eee dom Sk hee 72
Py fe curr eed (REAS « Fs 8 |.--do_.... 23 | = (aes Gn... 2 eas es 72
EIGHTH GENERATION, 1914-15.
1] Aug. 17] Aug. 24 7! Sept. 16 | 23 | 30 | Muscat XXK__.._______ 70
rd ae i tae We "=e rf pe Pree 23 | = 1 Rene dps. 25502 I Tees 7
See dotecss Aug. 25 8 | Sept. 26 | 32 | sil) Beeee et Gb 225. eS ee 69
A gee ie doe 8] Mar. 26 213 | 1 ae dp. 5-8. 3 ee ee 3 72
Bat ee Re ee 8 | Mar. 30 | 217 5 p28 i) Seu ES SARIS Sse 3 72
61-2: do.22241- dos 8] Apr. 3 221 229 j_._.- 03 ee eS ee 37
fe ee does 8| Apr. 4} 222 | 230 | ____- G0! ee A ae 372
Si 0022 rdgetac 8 (4) oR: 2252 Fe ee ee Gos Se eS ee 3 72
9 meet [eel Aug. 26 9 (4)? Sica ftteeeee eee | Seven 0D 2 SL eal 3 7.
NINTH GENERATION, 1914-15
1 | Sept. 16 | Sept. 27 | 11 CQ ee eee Mipscal Raker tea eee 372
3a peat t Pree PE do-.- 11 | Apr. 11, 196 | 207 j=---- 022: 5.2.0 Pee 372
NINTH GENERATION, 1915.
1| Mar. 31 | Apr. 19 | 19 | May 22 33 52 | Carignan XXTX...._... 57
242 do. -|sdo Sess 19 | May 23 | 34 BS luce? ip set potas Sy 57
31. -do* _-|._. do= =| 19 | May 24 35 2 eee “eens et Pa a 57
a Peidos=- fo) do-2 4 19 | May 25 36 | = ee (RES CREO DERI i 57
TENTH GENERATION, 1913.
|
| May 23| June 3 | 11 | June 24 21 32 | Carignan XXIX...._... 66
2 | May 27 | June 6 10| july 1 23 35 | Zinfande] X XTITA _____- 67
ELEVENTH GENERATION, 1915.
1 | July 9 | July 15 | 6| Aug. 10 26 32 | Zinfandel XXTITA______ | 73
Dake ea eee ae Se Salty 3290! ee | Garignan A X1X.-- Se
3 | See a (ie en | ae Fase pst Sea eee ee) (eee fe) (Ea O52 ke 2 = es eee
| | | |
TWELFTH GENERATION, 1915.
i
i); Aug. 2] Aus. 9 7 | Sept. 8 30 37 | Zinfandel XXXVI_...... 72
2 © Gos 3 Aug. 10 8] Sept. 9 30 | S22 Pees 10.33 72
= Hl fae 1! eee | Aug. 9 7 ee . 10 | 32 | sl) eee do... eee 72
4| Aug. 4] Aug. 11 7 nee 30 | “7 oes dp. oe ee 72
5| Aug. 16] Aug. 24 2 ple eS ee Se | Zmfandel XXTA_- [ae
Dy eS Aug. 25 }| [Gare ke ee ees (RS Aerts 1 do See oe oe
7 | Aug. 17 oS ee es a a do.) See ae aoe
8 | Aug. 18 | Aug. 27 RUE eat ee ee aCe do. 22 tee ee
9} Aug. 19 }-_-do-_...- £5, |S eg [eoee ste coe ese Sas os eS = Go). Se Se oe
3 Indicates average temperature of incubation period alone. * Died, 1915.
|
THE GRAPE PHYLLOXERA IN CALIFORNIA. 63
For the first generation, eggs deposited by adult hibernants were
secured from a Zinfandel vineyard, and thereafter only eggs de-
posited in the cages and of known generations were used in the inocu-
lations.
The average growing periods of the summer generations of wing-
less aphids varied from 34.5 to 18.25 days, but in all except two gen-
erations this period ranged between 18.25 and 24.20 days. Individ-
uals varied between 36 and 10 days. The winged forms developed
more slowly than the wingless, nine individuals averaging 343 days.
The hibernants developed in an average of 6? months.
Eggs were placed for the most part on roots never before infested,
and tuberosities usually followed rapidly after the hatching of the
larve. Nodosities were formed upon side rootlets. The main roots
were all between one-sixth and one-third of an inch in diameter.
It was found that about 40 per cent of the larvae remained on the
exposed portions of the roots, the rest finding their way to the other
portions. In spring a large percentage and in summer and autumn
a smaller percentage of larves settled close beside the eggshells from
which they had issued. In spring the larvee did not display a tend-
ency to roam, but in summer and autumn they wandered consid-
erably, especially if the root had begun to decay or was drying too
rapidly. Similar conditions occur in vineyards, and it is in summer
and autumn that the typical wandering larve are found.
Excluding the winged migrants and the hibernated individuals,
the summary of the growing period of all the phylloxerz developing
on living roots during the years 1913, 1914, and 1915 is recorded in
Table XIV.
TABLE XIV.—Summary of Table XIII.
Number of individuals = —:sieeiiiueiewe seek ee 2 114
Average period of growth _ i a Bis Ti SY at hl 'S UO Set aR ena a @ays22 a e22a05
MERIT IMI PELELOC Cty STO; yyls la eee at oe i dol 456
MinimMuUn perOdwor 260 Wilson Sen ee ey ee Corer rdlO
Taking into consideration the individuals removed before they
attained their full development, the average growing period is to be
estimated at about 25 days. The cellar experiments with severed
pieces of roots in 1911 and 1912 combined yielded an average of
30.57 days, and the experiments in the cellar and incubator combined
in 1913 averaged 34.16 days. The cellar temperatures of 1911 and
1912 averaged about 14° F. lower than the combined cage tem-
peratures for the period 1913-1915 for the months from May to
October, inclusive. The cellar temperatures for 1913 averaged about
14° lower than the incubator temperatures for 1913 and about 3°
higher than the cage temperatures for that year.
64 BULLETIN 903, U. S. DEPARTMENT OF AGRICULTURE.
In the cellar and incubator during 1913 the phylloxere developed,
on the average, more slowly than in the cellar during 1911 and 1912,
notwithstanding higher temperatures in 1913. This resulted from the
fact that the food supply was much more succulent in 1911 and 1912.
Likewise the phylloxerze developed much more rapidly in the cages
in 1913-1915 than in the cellar and incubator combined in 1913,
when the temperatures differed slightly (the difference in favor of
the cages being about 1° daily). This also was due to the superior
food of the living vines. In comparing the phylloxera development
in the cellar in 1911-12 with that in the cages in 1913-1915, it would
appear that both temperature and food influenced the more rapid
development observed in the cages. For 1911 alone the average grow-
ing period was 29.37 days. This growth took place on succulent roots,
to all appearances as succulent as the living roots upon which were
reared the 1913-1915 phylloxere, which averaged about a 25-day
period, under a temperature averaging 44° in excess of that obtain-
ing in the cellar in 1911. It would be natural to ascribe the faster
growth in the cages to the higher temperatures, but in view of the
discrepancies noted above in connection with the 1913 cellar and
incubator observations, the writers are inclined to believe that the
living roots afforded better nourishment to the phylloxere than did
the severed roots of 1911 and that the higher temperatures of 1913
had less influence than might appear in bringing about such a dif-
ference in the growing periods.
Excepting for a few isolated instances, the phylloxere on living
roots developed more rapidly on nodosities and tuberosities than on
the normal surface of the root. On nodosities development was the
most rapid, noticeably more rapid than on tuberosities, and the more
fleshy the swelling the more rapid was the aphid’s growth. .
DESCRIPTION OF STAGES.
The egg—When first laid, the radicicole egg (Pls. VIII, g; IX,
i, 1) is lemon yellow, about twice as long as wide, oval, both ends
rather bluntly rounded, the micropylar end a little more abruptly
so. Thirty-six eggs laid by newly matured adults August 30 and
September 6, 1911, averaged 0.348 mm. in length and 0.173 mm. in
width, with maxima, respectively, of 0.36 and 0.18 mm., and minima,
respectively, of 0.34 and 0.17 mm. Of 25 eggs laid by overwintered
radicicoles near the end of their laying period, the maximum length
was 0.32 mm., the maximum width 0.18 mm., the minimum length 0.20
mm., and the minimum width 0.12 mm., the average length 0.26 mm.,
and the average width 0.14mm. Thus it appears that the size of the
eggs laid by individuals decreases toward the end of their egg-laying
Bul. 903, U. S. Dept. of Agriculture. PLATE VIII.
KO
or my
i) Cuil (
‘
anc
ET Wall
(;
t {
AN Wat
y)
4 LY
Wy
Ws
7s
Gye a_ LEE Ty (Smee
4f
Can(i ”
THE GRAPE PHYLLOXERA IN CALIFORNIA.
Phylloxera vitifoliae: a-e, Winged migrant; a, dorsal view; b, antenna; c, basal sensorium of
antennal segment III; d, hind leg; ¢, beak; f, male egg; g, radicicole egg; h, i, female eggs;
j, k, l, sexed female; 7, enlarged ventral view showing contained winter egg; k, antenna;
l, newly hatched female; m, mature male just after casting last skin.
THE GRAPE PHYLLOXERA IN CALIFORNIA. 65
period. Toward the period of hatching the egg becomes darker and
the eyespots of the embryo become visible.
The larva—In hatching, the young larva (PL. iD. g, h) splits
the eggshell from the icone lengthwise to about three-fourths
of its length. This splitting is more or less gradual and is caused
by the thorax and head of the young phylloxera bursting the shell
and then gradually enlarging the crack. The larva poises itself at
an angle of 45°, with legs and antenne appressed to the body, and
slowly eases its way out. It seems to rely simply on a slow side-
wise body movement to free itself of the shell. When freed,
spreads the appendages and is then able to walk off. The newly
hatched larva is of a pale lemon yellow, with dark claret-colored
eyes, composed each of three circular facets and placed in the form
of the angles of an equilateral triangle. The body segmentation is
quite distinct, more so than in later instars. The shape is oval and
very flat. The antenna, as in all forms of the grape phylloxera, are
three-jointed. The terminal joint is twice as long as the two basal
combined. Near the apex of the third joint occurs a circular sen-
sorium. The beak in early generations reaches to the penultimate
or antipenultimate body segment, and in later generations protrudes
beyond the caudal segment of the abdomen. The legs and antenne
bear hairs. Table XV gives measurements for five newly hatched
individuals.
TABLE XV.—Measurements of newly hatched radicicoles of the grape phylloxera,
Walnut Creek, Calif., Oct. 23, 1914.
Maxi- Length of antennal joints.
Pai E Length | mum | Length Length | Length Length
Individual No. : — | of hind | of hind of sen-
of body.} width | of beak. (emine FibiA :
of body. ; : 1 2 3 sorium.
Mm. Mm. Mm. Mm. Mm. Mm. Mm. Mm. Mm.
1 See eee es 0. 359 0.176 | 0.1964 | 0.0679 |. 0.0571 |_......-. 0. 0161 OR07050 | sees
Dh ie ie oy Aes mde! saa 32 179 2036: teen ee | ees 0. 0169 014 6250 |Feeereeee
Ne ie aca ei es ae ae et mn em Se Se SSDs Ol a» MARIE 0562 . 0429 . 0214 0196 O680F eee
Za: er ees Sg ES a 359 189 2152 0580 . 0491 0232 0180 0/055 |hee eee
15) SRR ae ee enerys 341 190 2107 0566 0455 0188 0188 0634. 0. 0231
SS ee ae, BCE: A ra a te | Re |e = oak ae 0554 0491 0179 0152 0670 0225
The young phylloxere hatching in spring have shorter beaks than
those which hatch in the fall, the beaks in spring averaging in length
about 0.155 mm.
The first molt does not take place until more than half of the grow-
ing period is passed. The molting of the radicicoles is a procedure
quite similar in detail to the hatching from the egg. After each molt
the individual for about 24 hours is brighter in color than at any
other time during the instar. After the first molt the phylloxera
changes from oval or suboval to pyriform in shape (PI. IX, 7, /).
1900°—21—_5
66 BULLETIN 903, U. S. DEPARTMENT OF AGRICULTURE.
Table XVI gives measurements for four individuals of the second-
instar radicicole.
TABLE XVI.—Measurements of second-instar radicicoles of the grape phylloxera,
Walnut Creek, Calif.
= Length of antennal joints.
: Tense Bake Leneth | Length | Length 6 J Length
Individual No. of Backs sidehn lot ake of hind, | of hind: |= ——— = a | OSG
: of body. ‘| femur. tibia. 1 2 3 sorium.
Mm. Mm. Mm. Mm. Mm. Mm. Mm. Mm. Mm.
1 eee See as 0. 419 0. 234 0.154 | 0.0625 | 0.0526 | 0.0190 | 0.0204 | 0.0586 |.........
POO CSSoEETebeaense= SAASA Res al sees - 0624 - 0518 - 0205 - 0205 0589) |e eee
Segoe sok eae saree 439 257 1733 EES Sal ir eae Se ni Dees ordi te, Moelle che Bn Sheva (eatin Se S| aco t
1 Telescoped.
The roughened tubercular areas on the dorsal surface are more
conspicuous after the first molt, and a rapid increase in bulk is
apparent during the second instar.
The second, third, and fourth molts occur at practically equidistant
periods. Under highest temperatures and optimum food conditions,
these instars are passed in about two days apiece. Under a tempera-
ture of 58° F. from three to eight days elapse between molts, the
average being about five and one-half days. |
Table XVII gives the measurements of five individuals of the
third instar.
TABLE XVII.—WVeasurements of third-instar radicicoles of the grape phyllozxera,
Walnut Creek, Calif.
; Length of antennal joints.
ieee Mie Leneth | Length | Length 2 : Length
Individual No.1 | ofiGay.| width | of b ic | ofbind | of hind |-—=—>] || olisen=
of body. femur. tibia. 1 2 3 sorium.
Mm Mm Mm Mm mM. Mm Mm Mm Mm
1 ees a) re PO a Te 0. 592 0. 303 0.178 0.0699 | 0.0607 0. 0202 0. 0321 0. 0616 0.0
INSEE es Se ae etn 524 312 GAS) aes a eee ee 0252 0207 0568 0144
Bical ll eee mene 522 332 179 0739 SO622 12222 ore Nie es ees eee gus
Co Son ane Ss eee ae 649 355 155 0732 . 0687 0241 0205 0634; \>22 Sees8
oC cant a Fee nee cy ead 0758 0660 0197 0187 0589 0177
is Bo Cee ee SS eee 648 371 145 0741 0692 0206 0194 0598 oe
SS Ee ary (EM Werar sua canes 2 = oC Ae Pe SS aie el tae |e pea ihe Ses SS a :
1 Individuals 1-3, newly molted; 4, two days after molt; 5, three days after molt.
During the third instar (Pl. X, a, 6, c) the increase in bulk con-
tinues rapidly. The dorsal tubercular areas are larger than in the
previous instar, but in color and shape no differences appear.
Table XVIII indicates the measurements of seven individuals of
the fourth (penultimate) instar.
THE GRAPE PHYLLOXERA IN CALIFORNIA. 67
TABLE XVIII.—Jeasurements of fourth-instar radicicoles of the grape phyl-
loxera, Walnut Creek, Calif.
i- Length of antennal joints.
By Thenetti et Length | Length | Length 2 ‘ Length
Individual No.1 | or} dy.| width | of beak Gffiin dy Not hind) | iran pace inne an Ouse l-
of body. femur. | tibia. 1 2 3 sorium.
Mm. Mm. Mm. Mm. Mm. Mm. Mm. Mm. Mm.
NS ee See ee ee 0. 919 ULI Saeco saes 0.0848 | 0.0687 | 0.0321 | 0.0259 | 0.0669 |.__.-....
7A as Seen Ee ee 851 BP et Meee eet eS ra ee a a - 0321 0277 OS TEN
BS Cees Be eee 824 AS) S| been, Cece 0830 0749 . 0276 0241 0768 0. 0212
Cases Ge cece ma 615 500 CO) (PA hea ll ve 8] We 0306 . 0261 0748 0167
BE Cotsen Gare ete Sen ad bconecer Istorasane LG Zig Pegs ieee eek Ae Su yah ees 0297 . 0248 0721 0162
es Se ee ee eS - 753 426 160 0802 LO 637/ Fa E| S eeee | oe e e
(raelsas SOF oe Seon POR sd, OOM | cee tee hone tell ete utes rel) Becta eB Weta Peectewseec |e awes | eyeee Sues esl ae Geet (RE Nae gS
|
nh 1-3 were measured toward the end of the instar, and individuals 4-7 very shortly after
2 Maximum height, 0.3 mm.
A very obvious growth takes place during the fourth instar (Pl. X,
g-j). At the end of this instar the phylloxera casts its last skin
and issues therefrom as an adult. The adults, except immediately
following the molt, are never as pale as the immature forms. They
may be distinguished from fourth-instar individuals by two longi-
tudinal furrows on the thorax and by the relatively larger dorsal
tubercular areas. The color varies from a light green to a dark
purplish brown in living specimens. This variation is to a great
degree dependent on the food supply. On fresh, fleshy nodosities
the insects mostly are pale green with the tubercular areas very
noticeable. On tuberosities, or on the normal surface of a vigorous
root, the color is yellowish green, olive green, or hight brown, with
the tubercular areas often less evident.
On roots of poor quality the adults are brown or orange and the
tubercular areas hardly perceptible to the naked eye. After weeks
of egg production old adults become brown or purplish brown. In
shape the adults while not engaged in egg laying are hemispherical
or short oval, about equally rounded at either extremity, but while an
egg is being passed the insect assumes a pyriform shape and the
caudal end is much tapered and extended.
Mature radicicotle.
Pl) (Xs @0; ¢:
Color varying from pale green and pale yellow to deep purplish brown, de-
pendent on character of food and age of individual; shape hemispherical,
short oval, pyriform while passing the ova; body obscurely glabrous, often
appearing to be coated on the dorsum with a very fine whitish powder; under
side of abdomen paler than upper. Body about twice as long as wide, widest
at middle of mesothorax ; highest at about cephalic third; body flattening both
cephalad and caudad from this point. Head with dusky central area; eyes
dark red, each composed of three circular facets, arranged in form of an equi-
lateral! triangle; antenne pale, not quite reaching posterior margin of head,
composed of three joints, of which the two basal are subequal in length but
ep Rg ee a Toe eee eS eo Aer ee ase a ee ea ee ee
68 BULLETIN 903, U. S. DEPARTMENT OF AGRICULTURE.
joint 1 wider than joint 2; third joint about twice as long as the two basal
combinea and bearing a single oval sensorium near apex; all three joints bearing
hairs. Beak pale, base and tip shining and dusky, reaching to second or third
abdominal tergite; in specimens examined after they had transfixed the beak
into the roots, this organ appears to be shorter, due to the telescoping of the
sheath from the action of transfixing.
Mesothorax largest segment of body, twice as long as prothorax, which is
next largest; mesothorax divided into two sections by transverse fold. Thoracic
segments having median portions raised above lateral portions by means of
two longitudinal curved folds. Metathorax very similar above to any of first
five abdominal segments. Legs in pale specimens slightly darker than abdomen,
coxe dusky.
Sixth abdominal segment produced conically at each of its posterior angles
and narrowed basally; caudal segment twice as long as broad, bluntly rounded,
with a small central emargination and fringed with a marginal row of pale
weak hairs.
The dorsum of the body bears six longitudinal rows of dusky circular tuber-
cular areas, which under magnification appear as thickenings and roughen-
ings of the epidermis, and each of these is surmounted by a single spine.
Table XIX gives measurements of the adult radicicole.
TABLE XIX.—WVeasurements of mature radicicole of the grape phylloxera,
Walnut Creek, Calif.
i Length of antennal joints.
- Length I ength 5 t a joints
ae 5 Length | mum | Length = : oe ee
Individual No. ofbody.|} width | of beak. of hind | of hind of sen-
Mm. Mm. Mm. | Mm. Mm. Mm. Mm. Mm. Mm.
[i= Ne a Se ae 0. 854 Ths | i Ee | 0.0795 | 0.0786 | 0.0223 | 0.0251) 0.0661 0. 0224
pi ses ih prelet s e! a Sees | 0804 0759 0252 .0243 | .0660 . 0195
{OER ree nee See ee7S 5491 0.281 | 0839 .0748 . 0260 . 0230 . 0673 . 0196
3 idee ee ee eee 1.011 a i [raeae ic eae |, 0875 0768 0197 .0230 .0705 . 0205
lie Sas ae RE Toe . 997 Gal OE ire | |g oe: ears Bae reme ol Pane ae Fs erst
if 3t Eat ae Be . 942 Eee peer ae Ores Basi 2 eto ete o eee ne mel ES ae Sop al eee RSS Mesa ee
Geen Se cd 783 BOT lon | Cree eel | eae | een: ee ee ee jpiegnear
as oe GE ne RE OS 77 Toit Data eee PeReer rae cet [BE oy Sate ps 2 Sis A Se
ae eg ara . 763 | AGG ec” Seals. epee eal eee ees eres he acs (eas eS
7 0 pen aie > ea . 734 SAS US Aice ae Ye Gare Lee SIE SS eee ees
AQ RCS ee Ee 714 SUC G alam (eo Mas Cee eee aay SDT eee bee eS Eee eae
faces FETE 712 SOP et SE One ees RS eee Fe ae ge Sa ss |e eS | +e eee
ioe 3 ee . 686 | SUS 46 eae eee area ee eo ree hia Cee eee cre
ADEE SERIE ried -631 | AAG la? Sig Nhe SRL LIT 2 a ee a de ee ee
Pee ees ao” 582 | 3 iy 1h caiman) mete etree) Apap an Mra rie tM ete ee eRe ee Rafe
Measurements of beaks from nine adult hibernants were made
March 18,1915. Of these six, fixed in the root tissue, measured 0.276,
0.243, 0.260, 0.252, 0.198, and 0.179 mm., respectively. The other
three, not fixed since casting their last skin, measured 0.329, 0.317,
and 0.299 mm., respectively. The basal joints of the rostrum are
telescoped when the beak is thrust into the root.
It is obvious from an inspection of Table XIX that the adult
radicicoles vary greatly in size. This variation occurs whatever kind
of food supply the phylloxere are getting, although the average size
is larger on good succulent food than on that of poorer quality. Indi-
viduals 5 to 14 in Table XIX were all taken the same day (Mar. 18)
THE GRAPE PHYLLOXERA IN CALIFORNIA. 69
from equally succulent pieces of severed roots. They show a con-
siderable variation in dimensions, but, being hibernants, their aver-
age dimensions are less than those of the summer generations under
equally favorable food-supply conditions; for among the hibernant
adults there always may be found a considerable number of small-
sized individuals which evidently owe their physical inferiority to
the vicissitudes of the long hibernation period. Radicicoles raised on
fleshy and succulent nodosities attain an average size of about 1 by
0.55 mm., those raised during the summer on other parts of the root
system average slightly less, and the hibernant individuals average
0.75 by 0.50 mm. ~
Radicicole molts——The radicicole, in common with other forms of
the phylloxera, invariably molts four times.
In 1914 and 1915 records of molts were taken, and Tables XX and
XXI indicate molting records of 20 individuals reared on severed
roots in the laboratory cellar during the summer of 1914.
TABLE XX.—WMolting records of 20 radicicoles of the grape phylloxera, summer
of 1914, Walnut Creek, Calif.
Indi Date of Date of Date of Date of Total ae
Paal Date egg | “firs First | second Second third urd fourth Foote BEOWG tere
Noe batched. molte instar molé instar. molt instar.| nolt. | tastar. eee pera-
Dee Gure
— |
Days Days Days Days.| Days.| °F
1| July 22| Aug. 6 15 | Aug. 9 3 | Aug. 11 2 | Aug. 14 3 23 68
NA OOS 2 AN a 16 do asad Oe 2 Okees 3 23 68
3 | July 23} Aug. 6 14 do 3 | Aug. 13 4 | Aug. 16 3 24 68
AW 6s calleaeCMoocn TPA San ees ee See Eo So le a peel Teaser | ie esl Meme eee Wc te hee eee Se
5 | July 24] Aug. 7 14] Aug. 9 2| Aug. 11 2} Aug. 14 3 21 68
6 | July 25} Aug. 4 10 | Aug. 6 2 ug. 8 2) Aug. 9 1 15 68
(| eee Oe |e Ones ee 10 |...do.. Zien dose 2 | Aug. 11 3 17 68
Sale doses | AtIe smo 11 | Aug. 8 3 | Aug. 9 Pe SdOS8 2 M7. 68
9) PE dol eee |edone 1 | peed Olav 3 | Aug. 11 3 | Aug. 13 2 19 68
TOR end Ones peed Ose. 11 | Aug. 9 4] Aug. 12 3 | Aug. 14 2 20 68
1 tdol =. Aug. 6 12 | Aug. 8 2 | Aug. 11 3 | Aug. 13 2 19 68
19 Ne Jy Se Sian clin eee 128 |e doss 2) \- do." 3 | Aug. 14 3 20 68
Tele douse.| PAs. 25 1 |e doe 3 | Aug. 9 1 | Aug. 11 2 Lz, 68
1A Bet omsns| PAIS S a7, 13 | Aug.10 epee a eal Rin ate Sea Vays reese cuba ke
eee Ose Aug. 8 14 |._..do. 2 | Aug. 13 3 | Aug. 15 2 21 68
NG: | saeCKe ovals stOssce 14 |...do. 2 | Aug. 12 2 eon 3 21 68
7 |eeadoee5.| Auge 69 15 | Aug. 13 4 | Aug. 15 2 | Aug. 18 3 24 68
18 do....| Aug. 11 17 | Aug. 14 3 | Aug. 17 3a Oe. 1 24 68
198 aden. Aue. 13 19 | Aug. 20 7 | Aug. 24 4| Aug. 28 4 34 68
LOT Sen (ears Ea eae Gaerne cod sae |edeacod son bacon noche se cecs| EL merciaey [ee sie ace isao 8 Agen ber Cae ee Ae a
1 Hibernant died unmolted Oct.11.
TABLE XXI.—Summary of Table XX.
Maxi- Mini-
Average
peniodts |ier rear) liye
period. | period.
Days. Days. Days.
ITSHINS Ar. LONG ivi duals: c= peeee ence santo ce we Me C8) os) 13.3 19 10
SECONGHMS Fars U Silay Give ua Se eee eee rene ee a cyt ER Nae a 2.9 7 2
Miirdiinstan sling VAdUalSeeee ey Meee ee eke er Eb eed NS 2a, 4 1
ROULEA ANS CATs U7 11 GLVi Ga) eee yrs tena ee By eo Sat oe iy 3 255 4 1
Developmental period livandividualss 22.5. ceeeeokce. ae eek. Pe 34 | 15
70 BULLETIN 903, U. S. DEPARTMENT OF AGRICULTURE.
All the individuals utilized in this experiment were reared on
severed pieces of roots in a petri dish under cellar conditions. In-
dividuals 19 and 20 lived on a much poorer root than the others, and
thus is explained the relatively slow growth (34 days) of the one
and the early hibernation of the other. Individuals 4 and 14 moved
away after their first and second molts, respectively. It will be
observed from the summary that the average period of the first instar
(13.3 days) is considerably longer than is that of the three succeed-
ing instars combined (7.9 days). The comparative periods of the
instars are about constant; that is, an individual with a short first
instar will have short succeeding instars and one with a long first
instar will have long succeeding instars.
The records of Table XX were made in midsummer at a tempera-
ture of 68° F. In the soil at such a time of the year the temperature
is higher and the development of the phylloxera more rapid, while
in spring and late fall the development is correspondingly slower.
The developmental period of the hibernated larve varies greatly,
not so much from temperature as from other causes. There is an
average period of two and one-half weeks from the commencement
of feeding to the shedding of the first skin, and after that an average
period of three weeks between the casting of the first skin and the
shedding of the fourth, the second, third, and fourth instars occupy-
ing an average space of a week each. As summer progresses the de-
velopment of the radicicoles becomes accelerated, as may be observed
from Table XXII.
TABLE XXII.—WMolting records of radicicoles of the grape phylloxera, March to
July, 1915, Walnut Creek, Calif.
Indi- Date of Date of | Sec- | Date of Date of Total | ANE | g
vid- |Dateegg! “first | First | second | ond | third | PDE) gourth |Fourth| grow- tern ee
ae hatched. molt. |!2St@T-) “mnolt. |instar.| molt. |!2S*"-| molt. SUSE. eA pera- | tion
3 | e:
Day Days Days. Days.| Days. | °F.
eee Mar. 19] Apr. 3 15 | Apr. 10 Apr. 16 6 | Apr. 22 6 34 | 58.25 | A.
Qe (as Ole25 | ADEs xd 1 fe) oH Eee dos: Gtl-=edor 6 34 | 58.25 |] A.
Seer do Apr. 8 20 | Apr. 13 5 | Apr. 18 5 | Apr. 23 5 35 | 58.25 | A.
Ae? ) Apr. 10 22 | Apr. 17 7 | Apr. 21 4 | Apr. 25 4 Bf eateh eal l Ise
Doeeee May 11] May 27 16 | May 30 3 | June 1 2|\June 5 4 25 | 61 B.
Oakes: (0) SxOoee 16 do 3. /22-d0! 2H se X0), 4 25 | 61 B.
Ue oes May 23) June 7 15 | June 10 3 | June 13 3 | June 16 3 24 | 63 B.
85-428 June 16 | June 27 11 | June 30 3 |July 1 1|July 4 3 18 | 65 C.
Ore ..-do....| June 30 14|July 2 2\July 4 2/July 9 5 23 | 65 C.
10 2--d0--.-| July 3 17 | July 6 3|July 9 3 | July 10 1 24 | 65 C.
|
The individuals enumerated in Table XXII were reared under
cellar conditions on equally succulent pieces of severed roots. Table
XXIT, both by itself and taken in conjunction with Tables XX and
X XI, indicates the influence of temperature upon the development
of the radicicole under equal food conditions. Under a temperature
of 58.25° F. the period of growth averaged 35 days, under an aver-
THE GRAPE PHYLLOXERA IN CALIFORNIA. 7A
age of 61.75° F. this period was 24.75 days, under 65° F. it was
almost 22 days, and under 68° F. it was lowered to 20.3 days
(individual on unthrifty root disregarded). Under the lower tem-
peratures all the instars are correspondingly longer than under the
highest midsummer temperature, but the first instar 1s proportion-
ately less lengthened’ than are those following it, a phenomenon
that becomes quite apparent in the case of the hibernants, provided
their first instar be considered in a restricted sense to cover only that
period between the time when they commence feeding in spring and
the date of the first molt. The hibernant feeds for two and one-half
weeks before and for three weeks after its first molt, while in mid-
summer the larva feeds for 13 days before and for 8 days after its
first molt before it matures.
MAXIMUM AND MINIMUM GENERATIONS YEARLY.
In 1911 overwintered adult radicicoles matured at the end of
April, throughout May and June, and as late as July 7. Eggs of
the first generation were deposited from the end of April until
October 1. From the earliest eggs there followed seven complete
generations from hibernant to hibernant inside of the one year. No
observations were taken of the hatching of the late eggs deposited
by late first-generation phylloxere in September, but in the light of
contemporary observations on individuals of later generations there
is no doubt that a certain percentage of these late eggs would have
hatched into hibernants, thus giving a minimum of one. generation
per annum. In 1915, taking advantage of a hibernant which ma-
tured exceptionally early in the spring, it was possible to secure
eight complete generations within the year. Table X XIII records
the development of these generations.
TABLE XXIII.—Maximum series of generations of radicicoles of the grape
phylloxera, reared under cellar conditions, Walnut Creek, Calif., 1915.
Genera- | Temper-
Date ofegg | Dateofegg | Date insect tion ature
Generation No.
deposition. hatching. matured. cycle. (average).
Days. its
1 UD ap iis es 1 Je cd Supa ee a SU SF —— —,1914 | —— —,1914 | Feb. 26,1915 |..........]...-2.2.22-
Bhi SE eh are Ba ke Feb. 26,1915 | Mar. 19,1915 | Apr. 22,1915 55 58. 25
BS em ee RR hey SE RNS Nh Be Apr. 27,1915 | May 11,1915 | June 5,1915 39 61.20
Ce ene et ere i nh ee June 7,1915 | June 16,1915] July 4,1915 27 64.50
FRR SO ci A se er gk July 5,1915 | July 14,1915] July 28,1915 23 69.50
65 coe ees ont oe a oe a eee July 28,1915 | Aug. 4,1915| Aug. 23,1915 26 68.50
Ch es MO rs tah mad ime Beh wT ut Se Wg Aug. 23,1915 | Aug. 31,1915 | Sept. 23,1915 31 67.00
Se? RS BBO SORE Fed RE Ss Sept. 25,1915 | Oct. 7,1915] Oct. 27,1915 32 62.50
(0) os as lh a Ree anh 2 1 att APS ae RE Oct. 27,1915 | Nov. 10,1915 | —— —,1916 |..........|..........
1 Hibernant.
In this experiment the food supplied to the phylloxere was, as
far as one could judge, of equal quality and very nourishing. The
influence of temperature is noticeable.
72 BULLETIN 903, U. S. DEPARTMENT OF AGRICULTURE.
In observations with phylioxerz developing on living vines there
were secured in a period of three years 13 generations, an average of a
little over four generations a year, but had the earliest eggs of each
generation been successfully utilized, and had it been possible to
start the first of the three seasons with the earliest eggs procurable
in the vineyards, there is no doubt that six, ana possibly seven, gen-
erations could have been developed each year.
Considering that the hibernant generation occupies a period of
half a year, it is apparent that if seven generations are to be pro-
duced in a year, the other six must be passed in an average maximum
of one month apiece. In summer phylloxere have been reared from
egg deposition to maturity in 21 days, but in April, May, and Oc-
tober the cycle rarely falls below 35 days, so that in the six-month
period, April 15 to October 15, the average maximum cycle is roughly
30 days. ‘Thus, in the vineyard, even on vines that move early in
spring, it 1s probable that more than seven generations rarely take
place in 12 months. The period, October 15 to April 15, best rep-
resents the cycle of the wintering generation, although these dates
are somewhat arbitrary.
Under vineyard conditions it is always possible to find hibernant
phylloxeree as late as the beginning of June. It is also possible
to find insects going into hibernation as early as September 20. Since
the mature radicicoles deposit eggs for periods exceeding three
months, it can be seen readily that the latest eggs of a radicicole
hibernant maturing in June may develop larvee which proceed to
hibernate. A minimum of one generation a year thus may occur.
Observations indicate that this minimum of one generation 1s not
common, even on moribund vines with innutritious roots.
WANDERING RADICICOLE LARVA OR “ WANDERERS.”
By the term “ wanderers” are designated those forms (almost all
newly hatched larvee) which forsake the root on which they issued
from the egg and seek to reach the surface of the soil or to pass
through the soil itself, with the object of finding new food. ‘Those
that strive to reach the surface exhibit in their efforts a very marked.
positive phototropism. It would appear that their first movement
is simply one of ascending the root and that as soon as they are
brought into the focus of a ray of light they immediately make it
their goal, and thus finally ascend to the surface. The initial wan-
dering movement comes irrespective of hght rays, but as soon as
these rays are brought to bear the activity is very pronounced. The
conclusion is that the production of individuals destined to wander
is due to a combination of influences more than to any single influ-
ence—the crowded condition of the phylloxere in summer, the decay-
ing of the roots, especially the fleshy surface rootlets, found on
PLATE Xl.
A CRAG é
PM) AY)
FOO SIN
SSS
FAA
THE GRAPE PHYLLOXERA IN CALIFORNIA.
Phylloxera vitifoliae: a, Nymph, dorsal view; b, outline ventral view of same; c, enlarged
sensorium on antenne; d, enlarged tubercle with spine; e, microscopic structural view of
eubercles f, hind leg; g, beak showing structure; h, middle leg; 7, right antenna; /, left
antenna.
THE GRAPE PHYLLOXERA IN CALIFORNIA. es
phylloxerated vines, the rising temperature, and the intrinsic vigor
of the vine encouraging emigration.
Apparently the young produced from the eggs deposited by over-
wintered females do not become wanderers, but those of later gen-
erations may, and many wandering larvee produced late in the au-
tumn settle on roots and hibernate.
Wandering larve play an important part in the diffusion of phyl-
loxera.
THE NYMPH AND WINGED FORM.
DEVELOPMENT.
The individuals which are destined to become winged are termed
in their third instar “ prenymphs” and in their fourth instar
“nymphs.” They are produced from eggs deposited by adult radi-
cicoles, and until after their second molt differ in nowise from the
individuals destined to remain wingless; neither is there any dif-
ference in the eggs from which the two types hatch. In their third
instar the prenymphs (Pl. X, d, e, f) differ from the radicicoles of
that instar in that the former have more elongate and narrower bod-
ies and longer antenne and legs. The prenymphs are generally pale
greenish yellow, and their appendages appear quite dusky in com-
parison. Table XXIV gives measurements of four prenymphs.
TABLE XXIV.—Measurements of prenymphs of the grape phylloxera, Walnut
Creek, Calif.
Maxi- = Length of antennal joints.
sane Length | mum | Length Length | Length Mi, Length
Individual No.} Sisal atin lan aane of hind of hind of sen-
y- of body. ‘| femur. tibia. 1 2 3 sorium.
ee a nemees aeerese Si- 0. 805 0. 405 0.357 | 0.0948 | 0.0821 | 0.0330 | 0.0268 | 0.0839 0.0196
Beste iota) otersoetsatere)| rere reeere 0939 - 0839 0321 0277 0889 0193
Deiat eR iaeias heme bee 660 325 193 0946 0713 0306 . 0279 O78) Nanedesos
Say alerbishate lle: srevaras optetel| Sispeensete ated areisicrs aml Ste lave e/a aioe 0306 . 0279 OONGH eee eee
SA Sine eeee cae sci 541 . 300 150) | ey Se lS Sec eas 25 |e arene (a el te cae SN ae a ea
Ca eS Se 555 DSA Reeeee ey reiete lleve rate sretat ete fajeratotennyel ball mare: eicte take eres era eros Lesverevaten eel [caveat este aes
b; Se 1, just before molting into nymph; individuals 2 to 4, very shortly after molting into pre-
The prenymph molts into the nymph or pupa. The pupa is the
longest of all forms of the insect and is easily discernible on the
root by the presence of wing pads, even just after it has molted from
the prenymphal form, and has a greenish color. Immediately after
the skin is shed, these wing pads are yellow, but very quickly they
become gray or blackish. During the first few days of the nymphal
instar the insect is green or greenish yellow, and the compound eyes
are indiscernible, but as it grows it lengthens, becomes constricted in
the region of the metathorax, and turns orange, the mesothorax, how-
ever, remaining paler than the rest of the body. The compound
74 BULLETIN 903, U. S. DEPARTMENT OF AGRICULTURE.
eyes show their red pigment and soon become prominent. Legs and
antenne are relatively long, and the femora exceed the tibie in
length. At all times the rows of tubercular areas on the dorsum are
well marked. During the nymphal instar the insect shows a very
considerable growth; the newly molted individuals are quite fiat,
but full-grown nymphs are roughly cylindrical.
DESCRIPTION OF STAGES.
The nymph or pupa, full grown.
Pi xd text fig. 9> p.7sh:
General color orange or orange yellow; anterior part of mesothorax and ~
mesosternum whitish, or at least always noticeably paler than the rest of body.
Antenne pale yellow, extended but little beyond anterior margin of prothorax.
Compound eyes and ocelli dark red; former composed of large number of facets.
Head and abdomen bearing 4, thorax 6 longitudinal rows of dark tubercular
areas (coarse roughening of epidermis), each surmounted by a spine; wing pads
dark gray, grayish black, or rarely jet black; legs pale yellow, often with a
dusky cast; abdomen with 7 visible segments, mesothorax apparently bisected by
a transverse fold; beak very pale yellow, reaching to posterior coxe.
Measurements of 6 individuals are given in Table XXY.
TABLE XXV.—WMeasurements of nymph of the grape phylloxera, Walnut
Creek, Calif.
| ] |
Maxi- | Length TAseit Length of antennal joints.) pe
as Length | mum | Length | of hind | U8"? | ens.
Individual No.” | ofbody.| width | of beak. | femur. | bind | of sen-
of body. | a. | 1 2 3 sorium.
Mm Mm Mm Mm Mm. Mm. Mm Mm Mm
Merson ec ake ip 22 eee 0.3295 | 0.1500 | 0.1366 |......... 0.0402 | 0.1536 | 0.0223
2 as eee Bee ce OIe Ceag Hd oe 1464} .1384 0.0339 0350 | 1545 0224
fs Sea i oR BRON aaeeere ee 3600 1419 iE yi he expen © 0331 | .1455 0230
cae 5 | Se Og a eel 1438 iY oa ede 9 arses (Seay ee eG 0254
=e 55 See ee I 957 507 3339 1089 1071 0321 0339 | .1179 0223,
Pegi | sry a a be eg 8 in eas NS hy a 0304 0295 |. 1184 0232
2 rs oe eee Rai kd Bae Oe Wises (openers Pease eat eg ts ts beans PCS eb e
5 ese Re bod ae . 798 511 2695 1389 1252 0315 0309 1577 0198
See Gee eee * Sy Poa eee nes bee eres 5 [eee ened beep picts pe ene GN I Sa Ne eg A
Te a eens Ad Pana Bera} CuCl aes ene: (uemiic ny einen eh. i TTR EE! OER Gio So
Jon noone ee | 1.197 B5GO)|< 2 ces Bess Se la eee eae ee ea
1Individuals 1, 7, and 8 at end of stage; 4, 5, and 6 at beginning of stage; 2 and 3 about middle of stage
Newly molted nymphs average about 0.78 mm. in length and ma-
ture nymphs about 1.1 mm. The nymphs are always more active
than the immature wingless forms, wandering larve excepted. Their
eyes are well developed, as in the winged insect, and they have the
ocelli found in that form. The third joint of the antenne bears a
single sensorium corresponding to the apical one of the migrant, and
as the last molt approaches the migrant antenne show through the
nymphal skin, and thus the nymphal antenne appear to bear two
sensoria.
THE GRAPE PHYLLOXERA IN CALIFORNIA. 75
The adult instar of the winged form shows what is probably the
most highly developed form structurally of the phylloxera. The
winged insect is, on the average, slightly shorter than the full-
grown nymph. The antennz are longer than those of the previous
instar and bear two sensoria of about equal size. The comparatively
large wings are weakly veined but necessitate strong muscles in the
interior of the thorax. The legs are quite long and the tibize exceed
the femora in length. As the migrant sheds the nymphal skin, push-
ing it back and moving about its appendages, the wing pads appear
as little white rolls; the mesothorax is shining green, the head and
abdomen bright orange. The wings unroll as the skin is being passed
off the abdomen. As soon as it is entirely shed the insect moves off
and then pauses while the wings assume their final shape and posi-
tion, but remain whitish, hyaline, and limp. Soon, however, the
wings dry and the thorax hardens and darkens until it is almost
black. The head, prothorax, and abdomen remain orange, the head
with a grayish luster. The molting process occupies about 50
minutes. ,
The adult winged form.
Pl. VIII, a-—e.
General color orange or yellowish brown or gamboge yellow; head a little
dusky on the anterior half, especially the cephalic margin (front) ; ocelli dark
red; eyes brighter red than ocelli, compounded of many facets; ocular tubercle
small; antennz with three joints, not quite reaching the anterior margin of
the mesothorax, pale yellow, with apical fourth of joint 3 dusky gray; third
joint much the longest, considerably over twice as long as first two combined,
somewhat constricted beyond the basal sensorium and at extreme base; posterior
half of head, prothorax, and abdomen orange, yellowish brown, or gamboge.
: Thoracic lobes, scutellar lobes, scutellum, and mesosternum dark gray or
blackish; legs pale yellow, tarsi duskier; wing insertions, stigma, and veins
gray (at first greenish) ; stigma equal in length to about one-fourth of wing.
First discoidal arising from subcosta not far from basal angle of stigma,
stout, not attaining the wing margin by a space equal to one-fifth its length;
second discoidal faint, arising from the first vein or discoidal a little before
its center and almost reaching the wing margin at a point a little nearer to
the apex of the third discoidal than to that of the first; third discoidal faint,
arising from first vein close to its base and continuing with a double shallow
curve almost to the wing apex (the basal half of this vein generally obsolete).
Lower wings with the costal vein running parallel to the anterior margin
fer its whole length; cauda bluntly rounded, bearing a fringe of hairs; beak
slender, pale yellow, and almost reaching to second cox; two longitudinal
oval sensoria on the third antennal joint; basal sensorium situated at basal
third of joint, apical sensorium close to apex of joint. Wings borne. hori-
zontally, apparently the positions interchangeable, the right pair sometimes over-
lapping the left and vice versa. Abdomen widest at second and third abdominal
segments, where it is wider than the thorax, and about as long as head and
thorax combined. Body about as high as wide, not at all flat.
Table XXVI gives the measurements from 8 individuals,
76 BULLETIN 903, U. S. DEPARTMENT OF AGRICULTURE.
TABLE XXVI.—WMeasurements of the winged migrant of the grape phylloxera,
Walnut Creek, Calif.
et : :
Width Gad. SER a) Eee eee ae etd oe a 4 SLT 2 |e Ses eee -390
Width (thorax) Ly Sete Se ae ane 5 BO Ue ana e |yeneee ies 4 Kee
penta joints, length:
Antennal joint 3, base to apex of basal
SOTS ORT ae sae ee te eRe sees | Se . 056 . 06 : SOD89F); 05003 maaan
Antennal joint 3, length of basal sen-
PLO} ET ADD 06 Later pt Ph eS ae se ea (a eee . 026 . 030: z . 02 : SU2ZTO see
Antennal joint 3, length of apical sen-
SOTSUN yet ee oe eee fee, eh | ee : . 026 . 027 029i eee
Hinddentur dens the pense) fiers ce eS ! ; alt PA B48 02522 A Sees eee ee
Hind tibia, iength BEM ted Shanes | eee Ie ee ae S217, : 16 SOG 2S eco a ey ms | eee
Beak Meng y eee cate eT fe ease eee B73 aie aia 24s PR EAST be es
W ing expanse.
The prenymphal instar is passed in three or four days, in the same
time in which the corresponding instar of the wingless radicicole is
passed. The nymphal instar, however, is relatively longer than the
corresponding instar in the wingless form, and it is because of this
fact that the migrant takes longer to mature than does the contempo-
raneous wingless radicicole. The nymphal or pupal instar occupies
from 5 to 12 ers. the average being about 8 days.
The nymphs take more food than does the corresponding wingless
form, and after they have left a nodosity or tuberosity upon which -
they have been feeding, the lesion rapidly decays unless other in-
dividuals are settled upon it. The nymphs do not usually move
much during their period of growth, but if disturbed they move
quickly and display a negative phototropism when suddenly exposed
to light. The newly molted nymphs, however, often wander about
with apparent aimlessness. The full-grown nymphs just before
molting ascend the roots, seeking the surface, and transform on the
trunk or else find their way along the root until they come to a crack
in the soil, and crawling up the sides of the crack transform near the
surface. In glass sections cages, wherein the glass plates did not fit
very tightly to the soil, the nymphs were found sometimes crawling
up to within 2 or 3 iches of the surface and sometimes transforming
close by the roots as much as 17 inches below the soil surface, the
resultant winged aphids being compelled to find their way to the
surface. It was concluded that owing to the loosely fitted glass
plates of the section cages, which allowed abnormal light to penetrate
below the surface of the soil, the nymphs did not wait to ascend to-
ward the surface, but transformed below, their transformation being
governed by the strength of the light rays to which they were sub-
jected. It may be said that these section cages measured 9 by 24
inches, outside measurement, and allowed of a thickness of half an
THE GRAPE PHYLLOXERA IN CALIFORNIA. eal
inch of soil, which was a silty loam mixed with heavier clay loam.
In some half-darkened cages, containing potted vines, the nymphs
were observed to ascend to the level of the soil surface to transform.
On the other hand, occasional nymphs have been found to transform
on the roots as much as several feet underground, and many of the
resultant migrants failed to reach the surface of the soil.
HABITS OF WINGED MIGRANTS.
Occasionally it was noticed in the jars that migrants would thrust
their beaks into the roots and appear to feed. While engaged thus
they lower the head so as to allow the beak to penetrate the tissues
of the root. This organ appears to issue from the mesosternum,
because of the curvature of the sheath. The femora are kept hori-
zontal, and the antenne are usually in motion. While the insect is
walking the antenne are in motion. The migrants, so far as has
been noted, never feed after they issue from the soil. At all times
they exhibit strong positive phototropism. When placed in a room
they seek to crawl toward windows, and their activity is greatly
increased when placed in the direct sunlight. If placed in a petri
dish in the sunlight, they travel very fast and often take to flight,
and are capable of keeping up a walking gait for hours. If the
surface upon which they are standing becomes heated, they quickly
die. Ifa vine leaf or other shade-giving object is placed in the dish,
tne phylloxere will finally settle on the shady side of the object.
In the vineyard most of the winged phylloxerz were observed to
issue from the soil by creeping up the stumps of the vine. On arriv-
ing at the surface many of them passed to the soil and crawled
around aimlessly. Others crawled up the vine, and when they
reached a point of vantage, such as the end of a cane, they spread
and vibrated their wings, as though inviting the wind to bear them
off. Finally they launched themselves into the air and if they struck
a wind current were borne off. Often after spreading their wings
once or twice they turned about and crawled down the stalk, and
frequently when they launched themselves into the air no current of
wind caught them, and they half fell and half flew to the ground
in an oblique direction, but at other times they flew off strongly
without the aid of the wind. The migrants are capable of traveling
by flight and with the wind, as is evidenced by the experiments con-
ducted with sticky papers. (See Diffusion of phylloxera, p. 100.)
They have been taken on such papers at least 80 feet from the near-
est infested vine, and undoubtedly they may travel much farther.
In order to ascertain whether the migrants returned to the soil by
crawling down the stem of the vine, 26 migrants were placed on the
upper foliage of a small American vine (9 inches in height), on
78 BULLETIN 903, U. S. DEPARTMENT OF AGRICULTURE.
August 17, 1914. Around the base of the vine stem were placed
sticky papers, and the stem was encircled with glue. The vine was
kept indoors and was not exposed to wind currents. Six hours after
the phylloxeree were placed on the leaves, eight individuals were
caught on the paper. After 24 hours, 17 winged phylloxeree were
on the paper and 3 dead on the leaves, none having been caught in
the circle of glue on the stem. Thus the phylloxere had either flown
or dropped down and none had descended the full length of the stalk.
Since none of the individuals on the papers were over 4 inches from
the stem it would appear that they dropped rather than flew from
the vine. .
On August 22, 1914, 34 winged phylloxersze were placed on the
foliage of a riparia vine, 12 inches in height. This vine was potted
and sunk in the soil and exposed to field conditions. Around the base
an area of sticky paper 30 by 36 inches was laid. After two days an
examination of the paper showed on the leeward side eight winged
phylloxeree, occurring 164, 164, 16, 16, 12, 10, 6, and 14 inches, respec-
tively, from the stem, and one winged phy!loxera on the windward
side 2 inches from the stem. The remaining 25 were not recovered,
and probably fiew off or were blown beyond the paper. The location
in which this experiment took place was subjected to wind that blew
from one direction only. It is obvious that the wind was a factor in
the distribution of these phylloxere.
In the observations on the flying of the migrants it was found
that individuals would fly both in the sunlight and in the shade,
that very frequently they refused to launch themselves even in
bright sunlight and in all varieties of wind currents, and that they
appeared to take no definite direction in launching themselves. As
a general rule, the winged forms fly more abundantly in the sun-
shine than in the shade, and they are the more active the hotter and
drier are the conditions of their environment.
PRODUCTION AND RELATIVE ABUNDANCE OF MIGRANTS.
In 1911, in the course of rearing experiments conducted in the
laboratory cellar, the first winged forms were secured on August 2.
These had been raised on a heavily infested piece of vinifera root
and were part of the third generation of that year. In five localities
in central California nymphs were collected in vineyards from
August 3 to 19 and, judging from observations made in years fol-
lowing, it 1s possible that nymphs had been developed earlier in
that season. In the laboratory the production of migrants proceeded
until the end of November, but in the latter half of October and in
November only a few developed.
In 1912 no record was made of the earliest appearance of nymphs
and migrants, but they were found abundantly on young potted
THE GRAPE PHYLLOXERA IN CALIFORNIA. 719
vines (mostly resistants and American nonresistants) during Sep-
tember and October, and some were reared in the cellar during
August.
In 1913 the first nymph was observed, July 9, on the root of an
American vine, and at about the same time others appeared on
young resistant hybrids in pots. On the severed pieces of vinifera
roots kept in jars in the cellar nymphs occurred as early as July 12,
and on July 17 the first migrants appeared. This was the first year
in which experiments were conducted with living vines in cages,
and on these the earliest nymphs and migrants were reared on
July 20 and 28, respectively. In the experimental vineyard (Zin-
fandel) migrants were first collected about August 1, but some
nymphs were found on July 25 in a vineyard at Napa, Calif. In
general, migrants continued to develop until November, but after
the middle of October their production was scanty, and in the vine-
yard very few were found later than September.
In 1914 nymphs were first observed on June 16, both in the ex-
perimental vineyard at Walnut Creek and on roots kept in the
cellar. On June 18 a migrant was reared from a nymph collected
in the vineyard two days previously. On the roots of the vines
growing in cages nymphs were reared June 23. Throughout July
and August nymphs and migrants were abundant in the Zinfandel
vineyard. In September the numbers fell off rapidly and none were
found in Getober. In infested vines in pots migrants were secured
in considerable numbers throughout August and September, but
were much more scarce in October.
In 1915, in the material reared under cellar conditions, the first
nymph was observed on June 14. The day following, a nymph oc-
curred on the root of a young vine planted in a section cage. In the
cages containing living vines, the first nymph was reared June 23,
and in the experimental Zinfandel vineyard, nymphs were collected
June 22 and evidently occurred as early as June 15. In the vineyard
the production of migrants continued until the end of September,
and was abundant*from July 15 to the end of August. In the ma-
terial in the cellar jars, abundant migrants were secured throughout
the months of July, iene: and d September, and the rader ian con-
tinued until November 8.
In summing up, it may be said that in California the period in
which migrants are developed in vineyards extends from the middle -
of June until the end of October; that these forms appear in great-
est abundance from the middle BE July to the middle of Soman
(the hottest time of the year); and that the production is very
limited in June and October. In small vines in pots, especially if
consistent irrigation is practiced, the October production of migrants
80 BULLETIN 903, U. S. DEPARTMENT OF AGRICULTURE.
was frequently large. In the case of pieces of vine roots kept in a
cellar, abnormal conditions of food, temperature, and humidity fre-
quently arose.
The conditions which affect the relative abundance of migrants
are the following: Variety of vine, vigor of vine, humidity, tempera-
ture, condition of roots, character of soil.
Resistant and certain American nonresistant vines normally bear
the greatest proportion of migrants. These vines are the descendants
of the wild grapevines which formed, and still form, the natural
food plant of the phylloxera, and which were immune from serious
injury by reason of the fact that there was produced each year a large
percentage of migrants, while few or no wingless forms persisted on
the vines after the winged forms had departed. The wingless
radicicole forms during the summer fed only upon the terminal
rootlets, and when these decayed the vine was easily able to replace
them without suffering injury of any consequence. The resistant
vines of to-day, except in instances in which the roots have been
supplied with poor or insufficient soil, as is noted below, do not sup-
port heavy and continued infestations of wingless phylloxera, and
almost all the phylloxere born in summer and autumn develop
wings and become migrants. It may be said here that experimenting
with resistant vines grown in pots with soil unchanged for over a
year is apt to give misleading results, for as the soil becomes poorer
and insufficient for the increasing root system of the vine, fibrous
rootlets become scarce, and an abnormal infestation of wingless
phyloxere and a diminishing production of migrant phylloxerz en-
sue, thus approaching the conditions normally found on vinifera vines.
On vinifera vines and on many American nonresistants, such as
Isabella, Catawba, and Champion, the production of winged migrants
is never proportionately as large as that which occurs on resistants.
Well-nourished resistant vines have been observed to rid themselves
entirely of the phylloxere, the insects all departing as winged forms,
and in all cases under normal conditions, if any wingless forms
remain after the winged forms have all left, the number is very
small. On vinifera vines the total nymphal production has been
found to be over 33 per cent of the whole in season, although three-
fourths of the individuals produced on fleshy surface rootlets and on
nodosities have been observed to develop into migrants, and on suc-
culent pieces of severed root cuttings as large a proportion has been
reared.
In the vineyard the larger roots were rarely found to preduce a
number of migrants in excess of 25 per cent of the whole number of
phyloxeree simultaneously developed, and under unfavorable condi-
tions extremely few and sometimes no migrants were produced.
THE GRAPE PHYLLOXERA IN CALIFORNIA. 81
Under average conditions the proportion on the larger roots was
between 5 and 10 per cent. Regarding the American vines of non-
resistant type, a considerable diversity in the production of nymphs
has been observed. On some, like Moore’s Early, this production
may be proportionately very large, while on others, like Isabella and
Catawba, it may be smaller than on viniferse, as occurred in the ex-
periments in caged and potted vines. Vines like Agawam, Lenoir, -
and Delaware, vinifera crosses, bore about the same proportion of
nymphs as the vinifere, but among the labrusca types (Isabella,
Moore’s Early, Concord, Champion) there was considerable variation.
On resistant vines, the nymphs are developed on the nodosities, but
on viniferze and American vines of nonresistant type they are also
produced on other portions of the root system. On phyloxerated
viniferee, the most abundant production of nymphs occurs on the
fleshy and fibrous surface rootlets frequently observable in. the
vineyard. These rootlets are sent out in May and June, and often
become grossly infested with phylloxere in June and July. Toward
the end of July, they decay or dry out, and after that nymphs are
produced only on the larger roots and on nodosities deeper in the soil.
On the larger roots relatively few nymphs are produced before August
or after September.
Among vinifere the more vigorous vines produce the greater pro-
portionate numbers of winged forms. Badly stunted vines showing
several years of phylloxeration produce comparatively few, while
the recently attacked vines around the periphery of “spots” produce
large quantities. Viniferze vines in pots produce great numbers the
first year of infestation, but if the soil is unchanged in the second
and third years, as the vines become weakened, they produce fewer
winged forms.
As far as has been observed, all varieties of viniferze produce the
same proportion of migrants. —
It has been observed frequently that a humid environment stimu-
Jates the production of migrants and a dry one precludes it. This has
been especially noticeable in the cases of young vines in pots and of
the severed roots kept under cellar conditions. The late appear-
ance of the migrants in the experimental vineyard in 1913 as com-
pared with those of 1914 and 1915 was perhaps due to lack of moisture
in the soil in summer. The spring of 1913 was exceptionally dry,
and the ground became very dry by June, whereas in the two years
following, moisture was conserved in the top soil until July. The
total migrant development of 1913, however, although at first re-
tarded, was finally just about as large as those of the succeeding
years. To hold the severed pieces of roots, glass jars and dishes were
used in the cellar, and it was found that in the summer and fall
1900°—21 6
82 BULLETIN 903, U. S. DEPARTMENT OF AGRICULTURE.
a layer of wet sand placed in the bottom of the jar was conducive
to the production of migrants. When moisture was applied peri-
odically to filter papers, the production of migrants was greater
the more frequent the applications.
What effect, 1f any, temperature has upon the production of
migrants can not be shown except that they are produced during the
hottest months of the year. Contrasting the hot summer of 1913
with the cooler one of 1914, it was found that the production was
about equal each year.
Migrants are produced in greater numbers in soils which retain
moisture than in those which dry out rapidly. Otherwise no further
influence traceable to soil conditions has been noticed. Although the
general behavior of phylloxera differs considerably in relation to
different types of soil, as between these different types the production
of migrants does not appear to change.
In the season 1914, 12 vinifera vines were growing in cages. These
were inoculated in the spring, and six of them later treated through-
out the summer and autumn with fertilizers applied in liquid form
periodically. These fertilizers—nitrogen, potash, phosphoric acid,
and magnesium—were combined in a normal fertilizer and also
used in combinations in which one element was in marked excess.
The fertilized vines produced noticeably larger nymphal infestations.
In 1915 other potted vines were treated likewise, except that all
the fertilizer was mixed with the soil at the time of planting, and
the vines were not inoculated until a month later. In this series the
number of nymphs was no greater or less on the fertilized vines than
on the unfertilized.
Migrants formed part of radicicole generations 2 to 5, those of the
third generation being the most abundant. It was never observed
that any of the first generation (direct progeny of the hibernants)
became winged.
NYMPHICALS OR INTERMEDIATE FORMS.
The insects of the nymphical type are intermediate in form between
the winged migrant and the wingless radicicole. In their adult
stage they vary largely. Grassi (11) has figured and described sev-
eral individuals which represent stages in the variation. His speci-
mens varied from a type which differed only from the radicicole in
the possession of two or three extra eye facets and in longer append-
ages to one which superficially resembled a nymph in that it had well-
developed compound eyes and noticeable wing pads. This last type,
however, upon close examination, differed from the nymph as follows:
(1)The antenne (fig. 8; compare with fig. 9, antenna of nymph)
frequently bore two sensoria, as in the winged insect, but the basal
sensorium was less developed than in that form; (2) the wing pads
THE GRAPE PHYLLOXERA IN CALIFORNIA. 83
were not hard and straight and parallel to the sides of the body, but
bulged out and appeared rolled up and were soft, also sometimes con-
taining the sensory organs peculiar to the wing of the winged forms;
(3) there were no wing muscles in the interior of the thorax; and (4)
the structure of the vaginal segment of the abdomen was more devel-
oped than in the nymph. From this it appeared that this type of
nymphical was more comparable to the winged insect notwithstand-
ing its superficial resemblance to the nymph, and this conclusion
would be the more obvious when it is considered that the nymphical
is an adult insect of the fifth stage.
In Italy the intermediates are said to be quite abundant among the
nymphs in the season of the year (July to October) when the latter
are being produced on the vines. They were found to be especially
abundant on vines of the American type but also not uncommon on
vinifere.
In California, in the year (1915) in which were carried on re-
searches upon the intermediate forms, there was a very small avail-
able supply of infested American vines, and the observations were
confined chiefly to viniferee. On the American vines such as were
examined one nymphical was found. |
In looking over a series of slides made in 1914, a single nymphical
was recognized; the year following, during the nymphal season (June
to November), frequent examinations were made on vinifera vines,
end in all 15 intermediates were secured from these. The individual |
from the American vine (Wyoming Red) and nine of those on vinif-
ere were recognized through the medium of mounting large numbers
of insects and later examining them through the microscope. The
remaining six were discovered on the roots through the use of a
binocular microscope, and all of them had rudimentary wing pads, so
that it is likely that others of the type lacking these pads were ob-
served but not recognized as intermediates.
In the two years covering the investigation a total of 17 inter-
mediates came under observation. None of these was found earlier
in the year than the middle of September, and 12 were collected or
observed between September 14 and 27, 1915, and 1 on September 10,
1914. Of the 4 remaining, 1 was observed on a piece of root October
14, 1915, and 3 others October 27, 1915, 1 of which was in the fourth
stage and matured November 1. These 17 individuals differed
greatly one from another and represented all the types discussed by
Grassi and Foa. The types intergrade, and, in fact, no two of the
examples were alike. For the sake of comparison, they may be
divided into three arbitrary groups: (1) Those without vestige of
wing pads; (2) those with small buttonlike wing pads not visible
from above; (3) those with larger wing pads protruding (as in the
nymphs, fig. 9) beyond the lateral margin of the body and there-
84 BULLETIN 903, U. S. DEPARTMENT OF AGRICULTURE.
fore visible from above. In group 1 were two individuals collected
on young vinifera vines. One of them greatly resembled an adult
wingless radicicole, but be-
sides the larval eyes it had
two to three extra facets, and
the antenne and legs were
longer than in the radicicole.
The other was slender, re-
sembling a prenymph in
shape, and had about six ex-
tra eye facets, and one an-
tenna showed two sensoria.
Group 2 (fig. 6) had six rep-
resentatives, all with small to
very small rudimentary wing
pads invisible from above.
In all cases the antenne (fig.
Fic. 6.—Phyllozera vitijoliae: Intermediate of 8) and legs were long, and
type 2, ventral view. Much enlarged. one insect had two sensoria
on antennal segment III. In shape the individuals resembled wing-
less radicicoles. One specimen (from Wyoming Red) had no extra
eye facets, and the others from young vinifere had a varying number,
usually 10, although one had about 15. The remaining 9 individuals
came under group 3 (fig. 7),
and, because of their more pro-
nounced nymphlike characters,
these are more easily observed
a
i mn Ww
OO”
in hfe upon roots than are es
those of the other two groups, ae
and 4 of the 6 individuals rec- BZ D
ognized alive on roots were of = 2
this type. a
"Wy
hil
It is probable, judging from
random collections, that the
insects of groups 2 and 3 are
about equally abundant and
each somewhat more so than
those of group 1. All the in- ,
dividuals of eTroup 3 had rudi- Fie. 7 pRijtldgore vitifoliae: Intermediate of
mentary wing pads, in many type 3, ventral view. much enlarged: an-
cases almost as large as the wing tenna at right, more enlarged.
pads of the nymphs. They bulged out from the sides of the insects, ©
and were soft and appeared coiled (fig. 7) or curled. The com-
pound eyes were well developed, there being from 66 to 100 per cent
as many facets as in the nymphal eyes. In some cases the larval
a
THE GRAPE PHYLLOXERA IN CALIFORNIA. 85
eyes were absent, and in no case were ocelli discernible. In most in-
dividuals there were two sensoria on the last antennal joint, and in
one antenna there were two small basal sensoria and the usual
apical sensorium, making
three in all. The basal sen-
soria Were not in any case
as large as those of the ~ B
winged migrant. The an-
tennee and legs were about .
as long as those of the
nymph, noticeably longer
on the average than those of
the individuals of group 2, us
which in turn were longer fic. 8—Phyllozera vitifoliae: Types antenne of
than those of the two indi- intermediates. Greatly enlarged.
viduals of group 1.*° It would appear, therefore, that greater devel-
opment cf wing pads and compound eyes is complemented with a
lengthening of legs and antenne and a tendency to bear the extra
sensorium of the winged forms. The femora exceed the tibiz in
length.
There is among the intermediates a tendency toward asymmetry.
This was remarked in Italy and has also appeared in California.
One eye may have more facets than the
other; the lengths of antennee and legs
may differ in individuals, those of one
side being longer than their counter-
parts, and one antenna may possess
more sensoria than the other.
In two instances the fourth stage of
intermediates was observed in Califor-
nia. In one case an individual of group
3 molted from what appeared, under
the lenses of the bitiocular microscope,
to be a true nymph. In the other case
an example of the same group molted
from an insect which itself resem-
bled a nymphical; in fact, after the
molt the individual did not appear
peer eee ial On a to have changed its structure at all.
RecEntor comparison withintenmien: Lo boLn tourtneanmd fitthrainstars the
ae wing pads were large and “ fleshy.”
From three individuals, all of group 3, eggs were obtained. These
egos could not be differentiated from eggs laid by wingless radici-
coles. One nymphical deposited two eggs, which were lost. An-
me hy Pay i) ru
OOOO
ayy\ Ih eh) Dig 27)
LL fyi WB) iy Be ees W5=
a
10 The insect depicted in figure 7 is considerably less enlarged than that represented in
figure 6.
86 BULLETIN 903, U. S. DEPARTMENT OF AGRICULTURE.
other deposited two eggs, on September 28 and 29, respectively.
These hatched in 11 days, the resultant larve obviously being
radicicoles but surviving only a few days. The third individual
matured November 1, and between this date and November 10 it
deposited 10 eggs. After this it became weak, and on November 16
was mounted ona slide. The eggs were exactly similar to those laid
by wingless radicicoles, and two of them measured, respectively,
0.310 by 0.166 mm. and 0.297 by 0.168 mm. Seven eggs were trans-
ferred for observation to another root, and three eggs hatched in
from 14 to 16 days, the resultant larve settling down for hibernation.
One of these soon died, but the other two passed the winter in due
form, and matured in April, 1916. Both of them were typical
radicicoles and subsequently deposited many eggs.
In Italy Grassi and his assistants found that the great majority
of the intermediates were parthenogenetic, but one individual was
found to contain a sexed egg. In discussing the phenomenon of the
intermediates, they gave it as their opinion that the parthenogenetic
individuals were those which up to their third stage were destined
to become radicicoles, but in that stage changed their development
to that of winged migrants, while the character of their eggs had
been already fixed before the change and so remained parthenogene-.
tic. In the case of sexuparous intermediates the change was made
in the reverse direction, the larve at first being destined to become
migrants and, therefore, when they matured as nymphicals they
deposited sexed eggs.
In California the recorded eggs laid by nymphicals were all par-
thenogenetic, but the possibility of some of such eggs being sexual is
not entirely excluded, in the writers’ opinion.
The nymphicals do not leave the roots in the manner of the
winged insects, arid therefore deposit their ova on the roots. In the
c#8e of sexuparous nymphicals, the sexes and winter egg would
presumably develop underground. Whether in California such a
development occurs or not can not be stated from our present know]-
edge, but in view of the fact that for many years the leaf galls have
been unknown, it appears certain that such a cycle proceeds no
further than the winter egg.
DEPOSITION OF THE SEXUAL EGGS.
The migrants deposit eggs (Pl. VIII, f, h, 2) which are of two
kinds. viz, male and female, and from these eggs issue the true sexual
aphids. Sexual eggs have never been found by the writers in the
vineyard, either on vinifere or on resistant vines, although a large
number of vines have been examined. In laboratory experiments a
large number of sexed eggs have been produced. Considerable dis-
cussion has taken place among European writers as to the normal
THE GRAPE PHYLLOXERA IN CALIFORNIA. 87
location of the sexed eggs. Taking the sum of these discussions,
it appears that they are placed on the underside of the leaves and
more abundantly in the bark, generally between the year-old layer
and that of the current year, and are fastened to the inner side of
the former. Occasionally eggs are found at the base of canes where
the new wood joins the old, and rarely on the vine supports (stakes).
They are laid on both vinifere and resistant vines, but preferably on
the latter.
Observations were conducted in small cages, and in a few instances
on living vines in pots. In the latter instances eggs were found laid
on both the foliage and bark. Many different kinds of cages were
used and experiments with different degrees of light, moisture, and
temperature were conducted. Vine leaves and pieces of bark were
inclosed in the cages. As a rule, the migrants, though primarily
attracted to light, deposited their eggs in semidarkness. They laid
them on the leaves and more rarely on pieces of bark offered, but
often also on the sides, lid, and floor of the cages and in cracks. In
1911 the observations tabulated in Table XX VII occurred.
TABLE XXVII.—Sexual production of the grape phyiloxera, Walnut Creek,
Calif., 1911.
Number! pate of | Date of | Number
Number
of mi- Date and location of migrants. es deposi- |maturing} °fS¢xes
grants. posited ry HOE OL SORES tured 2
Zo} | PATI S462 RApPaALlanvanerlM POtmsaece sean eae ae neon LGR AICS OBER ES Weel
OZ) | PATS 7-2 Winliferanvine INsPObs = 2-2 asec ee eee ece ci Or lice Seek geal eee ee cereale eee
Gon Aue. 10-12 Ripaniaavineninspoweass:ssqes nse eeeeee 18 | Aug. 16 | Aug. 26 4
; Aug. 28 1
80!) Augst3; 14: Viniferaavine in) potess) 3225 552-2522.22 2|} Aug. 15} Aug. 30 1
Th NER ODENSE Soo oooe 0
Zon ATIC Los RApanla winein PObsenocsseeaeen eee aee eee Pill dse(GKO ee ees Bee 0
SOR PATI C= GseRApanianvine ln: PObisse sss neenies cea eeee eee Drillers COM aa ae a ear 0
30) Aug. 17:) Glass tube in drawer-+--.......02...22222- USE 8 Bal a Be ee Ce
83 | Aug. 18,19: Riparia leaves in petri dish ..._...-.... 7} Aug. 21 | Sept. 6 1
On| PASSA 22) beep ae 0
ZO PPART CA Sy yeaa 0
tA oS 19 sa beaviesiniupetrl disht saas42o5 pease e fae see 1! Aug. 19) Aug. 30 1
Cn PATIS Zo smILCA VES aM PCL GISMas sees sees secs esecsise 7 |) Aug. 23] Sept. 2 1
69 | Aug. 24: Riparia leaves in laboratory.......-.---.-. FA g 25) || 5455s 0
| eAN OSD GIES Severe: 0
Te PATI AS DAs Rene Fe oe 0
SING ROM ee he bee 0
ey PANT SAL 29 iy evar ay 0
30 | Aug. 25, 26: Riparia leaves in petri dish............. DO PAST S275) [ane pete nee 0
GaPATIet 828i | Kaew aee 0
1S | PATIO OO) eee eee 0
45 | Aug. 25, 28, 29: Riparia leaves in petridish.......... 1) SOO Bllepeaedcose 0
103) |) Sept. 2=17: Vinifera vine in) pot. 2... 2....--2c225-6- | 30 | Sept. 25 Oct. 4 1
Oct m5 1
Octee16 2
50 | Sept. 19-23: Riparia vine in pot..................- 15) Gultsep tesco eeeaeees 0
40 | Sept. 25-29: Riparia vine in pot_-...--...:.......... Ou Rist sejieete aie rea; CUS aes
1 Thirteen female and three male eggs.
2 All maturing sexuals were females.
TABLE XXVIII.—Summary of Table XXVIII.
INGINDEES OR MST AntGH es ewe ees LEU ee ee ly 734
INGIMDeOt Se xt: Cle GeNOsitediema es “airy Min yeh iris els ly ey aya
INDE Ty Oi SOxIa LiesosuhabGheG me tee. 5 5d Ue ey w 13
88 BULLETIN 903, U. 8S. DEPARTMENT OF AGRICULTURE.
Individual egg deposition by migrants, recorded for 5 individuals,
was as follows: 3, 2, 1, 4, and 3; average, 2.6. Obviously the great
majority of migrants died without depositing eggs. The eggs above
recorded were laid in from 2 to 9 days, the majority in from 3 to 5
days, after the migrants emerged from the nymphal skin. The great
majority of the migrants did not live more than 3 days after casting
their final molt, confinement evidently having caused premature
death. ,
From 100. migrants produced August 15, 1912, and placed on a
small vine August 20, a single egg, which failed to develop, was
deposited August 24.
In 1913 different types of cages were utilized in an effort to induce
a larger percentage of eggs and mature sexuals. The results were
not encouraging. From July 17 to October 17 migrants were placed
in the cages. During that time in some 60 experiments, 317 mi-
grants were used, 99 sexual eges were secured, and 7 sexed phylloxere
(all females) matured. The migrants in no case lived more than
6 days, the majority only 3 days, and quite a number did not move
their position after having been placed in the cages. In most cases
egos were laid singly, but there was one’group of 5, three groups
of 4, and several of 3 and 2, laid by single phylloxere. In two cases
egos, presumably of separate sexes, were deposited in the same group
by the same individual, but in all other cases it appeared certain
that the eggs laid by individual migrants were of only the one sex.
Judging from the size, about twice as many female as male eggs
were laid, besides quite a number (about 20 per cent) of eggs of an
intermediate size. No male or intermediate sized eggs hatched, but -
it was noticed that the male eggs, as they developed, assumed a
darker color than did those of the female. After a certain point in
the development, all the moribund eggs began noticeably to shrink
and turn dark brown. None of the eggs showed signs of infertility,
and within about five days of deposition hatching occurred and the
eyes and body segmentation were visible, after which the moribund
individuals discolored and shrank rapidly. Dead migrants were
found occasionally on the roots and sides of the cellar jars, beside
egos that they had deposited. In the vineyard such a procedure was
never observed, and therefore it is believed to be quite abnormal, and
probably results from the inability of the migrant to escape from the
cellar jar after having been overlooked in the periodical examinations
for migrants.
During the summer of 1914 a further series of experiments on the
production of sexual eggs took place. The temperature that year
was considerably below that obtaining in the years 1911 and 1913,
and this may account for the lack of sexuals maturing. In 1914 the
cages utilized in 1913 and some of other types were employed.
THE GRAPE PHYLLOXERA IN CALIFORNIA. 89
The experiments began June 27 and terminated September 7. Three
hundred and ninety-seven migrants produced a total of 148 eggs
from which no sexual forms developed. Thus the proportion of
deposited eges to migrants in 1913 was 1 to 3.2, while in 1914 it was
1 to 2.75, and in 1911, 1 to 4.3. In 1914 four migrants each deposited
four eggs, and three eggs were deposited in nine instances, but most
of the eggs were laid singly. In no case could it be definitely said
that eggs of more than one sex occurred in individual groups. About
three times as many female eggs as male were deposited, and about
one-fourth of the eggs were intermediate in size (probably males).
The winged sexupare died on the average two and one-half days
after they were admitted to the cages, or about four days after they
had transformed from the nymphal instar.
In 1915 experiments were continued, migrants being secured from
June 26 to October 27. Part of these were used in stender and petri
dishes, part in small circular rubber cells (3; inch high, 14 inches
in diameter) mounted on microscope slides with cover glasses for
lids, and a few on a living vine (Riparia). In the dishes small
pleces:of vine, bark, or leaves were placed, leaves of the Champini
being used mostly on account of the fact that the migrants prefer
to deposit eggs on a tomentous leaf. The effect of variations in
temperature and humidity was noted.
A total of 1,961 migrants deposited in all 472 eggs, and 52 sexuals
matured. Thus the proportion of eggs to migrants was approxi-
mately 1 to 4.15. In the stender and petri dishes and on the living
vine combined, 938 migrants deposited 167 eggs, a proportion of 5.6
to 1, of which 16 sexuals matured. In the rubber cells mounted on
microscope slides, 1,023 migrants deposited 305 eggs, a proportion
of 3.3 to 1, and 36 sexed forms matured. The rubber cells therefore
gave a greater proportion of eggs per migrant. Part of these cells
were kept in a cellar and part inside a slide box in a room of the
laboratory. The egg deposition was not appreciably different in
these two situations, but the sexes under the almost constant tem-
peratures of the cellar matured better than under the fluctuating
temperatures of the room. Part of the dishes also were kept in the
cellar and part exposed to light in the room. Those in the latter
situation averaged more eggs per migrant, but the proportion of
sexes which subsequently matured was similar to that of the migrants
and dissimilar to that of the eggs.
It appeared at first that exposure to light induced the migrants to
deposit a greater proportion of eggs and later appeared to have
prevented a large proportion from maturing. Judging from the
fact that the amount of light to which these eggs were subjected
during their development was not greater than occurs under natural
conditions, however, it would appear that this supposition is incor-
90 BULLETIN 903, U. S. DEPARTMENT OF AGRICULTURE.
rect and that the disproportionate mortality among the eggs was
caused rather by the uneven temperatures prevailing in the room.
The presence or absence of humidity had no apparent effect on the
deposition of eggs. Eggs and sexed forms developed better in dry
than in moist rubber cells, but in the dishes exposed to light the
converse occurred. Part of the migrants were stimulated to fly in
the sunshine before being placed in the cages, and deposited a some-
what larger average number of eggs than those which had not flown,
but the flight or nonflight of the migrants did not appear to influ-
ence the subsequent development of the eggs and sexes. In July
and the first half of August, when the temperatures reached a maxi-
mum, there was a higher average in egg production and in the pro-
portion of sexuals matured, yet during the period September 16 to
October 27, despite lower temperatures, a larger average proportion
of eggs per migrant and of mature sexes was produced than during
the intermediate period from August 16 to September 15.
On the whole, development was most successful where migrants had
flown and when eggs were kept in moderate light and in a moderately
humid environment.
The longevity of the migrants, the number of eggs deposited per
individual, and the proportion of male and female eggs laid coin-
cided with the results of experiments in 1914.
It is only necessary to consider the very small proportion of eggs
laid per migrant (in 1915, for instance, 1 to 4.15) and the very
small proportion of eggs which succeeded in developing into mature
sexes (in 1915, 1 in every 9) under artificial conditions to realize
how abnormal these conditions must have been. From observa-
tions made in California during 1915 the complement of migrant
eges was found to average 2.6, so that if all the migrants in the
experiments in that year had deposited their full complement, ten
times aS many eggs as were actually deposited would have been
obtained. European experimenters have had, for the most part,
similar results in their study of migrants in confinement.
In not a single instance was a migrant observed to deposit other
than a sexual egg, so the possibility of the occurrence in California
of a parthenoparous winged form may be regarded as excluded.
There occurs, however, a parthenoparous nymphical form, which has
been discussed above (p. 82).
THE SEXUAL FORMS.
The sexual forms (Pl. VIII, j-m), male and female, issue from
eggs deposited by the winged sexupare or migrants. These eggs
are of two types, male (Pl. VITI, 7) and female (Pl. VIII, A, 2).
Writers have attempted to recognize a third type intermediate in size
THE GRAPE PHYLLOXERA IN CALIFORNIA. 91
between the larger female and the smaller male egg, but these inter-
mediate eggs are apparently always of the male sex. Thus there is a
considerable variation in the dimensions of the male eggs, as, indeed,
there is in those of the mature male insects. According to Grassi
(11, p. 184-135) eggs producing females vary in length from 0.384
to 0.323 mm., and in width from 0.176 to 0.164 mm.; eggs producing
males, in length from 0.247 to 0.250 mm., and in width from 0.152 to
0.134 mm. He also states that eggs of the intermediate dimensions
are fertile and are of the male sex, and that male and female eggs
may exceed the limits in one dimension, but never in two. On the
average the female eggs were slightly larger than the radicicole eggs
and the male eggs slightly smaller, but intermediate eggs had meas-
urements identical with those of the radicicoles.
Measurements of sexual eggs, made in California in 1913, indicated
a range in length from 0.450 to 0.257 mm., and in width from 0.171
to 0.117 mm. A single female of these hatched (0.357 by-0.171 mm.).
In the light of measurements made in 1914 and 1915 it appeared that
eges of the sexes were similar in dimensions to those recorded by
Grassi for Italy, except that the range in sizes was somewhat greater.
The sexual eggs are bright shining yellow. The eggshell is very
thin and membranous, quite differently formed from that of the
radicicole. ‘The egg hatches after about four or five days’ incuba-
tion, the process of hatching consisting in the sloughing off of the
thin shell, the emerging aphid settling at the place of hatching.
The eyes and body segmentation become visible, and the undeveloped
appendages are carried under the body. The insect then undergoes
four successive molts, and does not move away until it is mature.
During the first three instars there appears but little change, except
that the body segmentation becomes more distinct. After the third
molt the appendages project slightly beyond the sides of the body,
but otherwise no visible change occurs. All the molted skins are
contained one within another, adhering to the posterior end of the
body, and when the last molt has taken place the adult moves away,
leaving the “nest” of telescoped skins and eggshell behind. It
sometimes happens that the adult is unable to cast off this pad of
skins. The mature sexuals are capable of running actively, and,
according to European investigations, they may live for some weeks,
thereby facilitating a meeting of the sexes. The sexuals take no
nourishment. The female is slightly larger and the male slightly
smaller than the newly hatched radicicole.
DESCRIPTION.
THE SEXUAL FEMALE.
Orange or orange yellow; antenne and legs dusky grayish; antenne longer
than those of newly hatched radicicole. Body a little longer and wider than
<<< eC ttC—CSOCOt Shr
99 BULLETIN 903, U. S. DEPARTMENT OF AGRICULTURE
the young radicicole. Caudal segment bluntly rounded. Eyes as in the radi-
cicole larva. When the adult issues the single egg within is small, but within
three days it becomes very evident (Pl. VIII, 7) and occupies in section an area
equal to about three-fourths of the entire insect.
TABLE XXIX.—WMeasurements of mature sexual females of the grape phyllorera,
1 2
| Mim. Mm.
Benveh: or bodys £ =F. PD cee Pe Saas eee oe eee Eee 0.357 0. 464
Maximum width DE DOD Ys 2 ee oe nn ce ee ee ee ee - 200 | 215
Length of “‘winter”’ egg ‘contained eee ee) et ee eee Se ees SAA ie Sake eee Ae NS Bp py eS
Maximum width of “‘winiter’ ers contained ss 226 5. s ee ee ee ee WT 2h. ae oes
Antennaljomnt Uricht. lenctht Se. Se ee ae Se ees ee 017 | . 0200
Antennaljoint 1, left, length Eo ene sacks ae ree bee Gog. Ce .016 | .0179
Antennal joint 2, right, lepetihis sth GS Fe BESO . $4 Vii es eee ee ees .013 . 0205
Antennaligints der denethe. <<. ae meen Sat St Renae a ho res a -013 0188
Antennal joint 3, right, Tengthe< cE e eet ef Fee Sees = SE Pee eee eo eae oe E05 . 0580
AMnGennalgoind 5) leit lene Gia oe ee ae as a 2 ee ee ee ee | . 053 0553
THE MALE.
Dusky orange, darker than the sexed female; antennez, legs, and genital
segment dusky grayish; eyes of three facets each, red; beak absent. Body
quite noticeably shorter, flatter, and narrower than that of the sexed female,
and shorter and narrower than that of the newly hatched radicicole. Genital
organ acutely conical.
TABLE XXX.—WVeasurements of mature males of the grape phyllorera.
Mm. Mm.
ihenGth otDod y 28 ee es ees os gp ae Se Si eee ere aaa | 0.260 0.334
Maximum width of Bede psa ane he en = a es aioe AE RS an ieee eg ar pS HRN . 094 . 154
Antennal joint 1, le GH oe eee Ed ie eat ieee pane Rw Sg ee pea ae 013s 2-2
Antennal joint 2 2, {NTE HA eae = 5 oie i tal Sg a eh a Re cess Leet ee I ee SO1S jes ee ee
Antennaljoint 3, length Se SaaS GS 2 Nap B A BE a See Se rte hee ee a - 065 | -O71
Hind tibia, length eI a ay Sao etd i a Be A ae, etree ag ae palit eat 5 Sh ae 5 046 So
Hind femur, | Cyt he Se ee eee ea es ete a A ee SE eee ae ook 2056, [bree ees
In confinement both sexes at first exhibit a positive phototropism,
but after a day of maturity they seek shaded places. At first they
are quite active, but later become sluggish. Undoubtedly they are
much less active in confinement than in the natural state.
Table X X XJ summarizes the development of the sexed form in the
summer and fall of 1911 and 1913. All those which reached the
adult state were females.
TABLE XXNNI.—Summarized record of sex development of the grape phyllorera.
Walnut Creek, Calif.. 1911 and 1913.
Number
of indi- | Days.
viduals.
AVerarenvicu bation Period = 52 == 2. = 225s 5a es ee ee 12 5
Averaceipostembryenic period (5._ 2622-222. = abe ee ee ee eee 12 5.83
Average period: ot development.2. -<...- 5 5.2.2 ee So Soe Soe Se ee ee 20 |- 11.05
THE GRAPE PHYLLOXERA IN CALIFORNIA. 93
In 1915, in all, there were reared to maturity 52 sexuals, of which
9 were males, 2 of these having hatched from eggs of intermediate
dimensions. These 2 males were noticeably larger than the other 7.
The majority of the sexuals were reared in darkness under cellar
conditions, the temperatures never averaging over 70.5° F. and in
one instance falling to 61.5° F. n
inns a cat ony “Al
agtig sel a =
(eee
Denes
o =
oo r
Pier fs ee ec : e st 3
few A i j i ; » SG
oe,
MEP DIG
Pi corte
'