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COTTONY-CUSHION SCALE Icerya purchasi Maskell -- Homoptera, Margarodidae -----
CLICK on Photo to enlarge & search for Subject Matter with Ctrl/F. GO TO ALL: Bio-Control Cases This particular
project was referred to by DeBach (1974),<PHOTO>, as the one
that, "... established the biological control method like a shot heard
around the world." The
cottony-cushion scale was discovered on Acacia
in Menlo Park, central California around 1868, from which is spread
rapidly. Folllowing its discovery on
acacia in northern California around 1868, by 1886 its effect on the new
citrus industry in southern California was devastating. Citrus growers tried washes and cyanide
fumigation but these were not effective.
Damage was so extensive that many growers abandoned or burned their
trees and real estate values plummeted (DeBach 1974). Alarmed California horticultural officials
began inquiries and enlisted the aid of Charles V.
Riley <PHOTO>, Chief of
the U. S. Dept. of Agriculture, Division of Entomology. Riley emerged as the dominant figure in
this project but others made more important contributions. The principal
foreign explorer involved was Albert Koebele, <PHOTO>, while D. W. Coquillett <PHOTO> played the
important role of receiving and colonizing the imported natural enemies. In 1885 Riley sent A. Koebele <PHOTO> to Alameda,
California, at a salary of $100.00 per month to conduct an
"investigation of the history and habits of insects of
California." About the same
Riley appointed Coquillett, a skilled amateur entomologist from Anaheim,
California, as field agent to work on the control of the cottony-cushion
scale around Los Angeles. In February
1886 both men were assigned to work together at Los Angeles on the scale. Riley was trying to
determine the native home of the cottony-cushion scale by correspondence in
order to begin the exploration phase of the project. By 1887 officials in California were also
trying to locate its source. DeBach
(1974) suggests that possibly stimulated by such correspondence, Frazer
Crawford, an entomologist of Adelaide, Australia, discovered in 1886 the
parasitic fly Cryptochaetum
(= Lestophonus) iceryae Williston, an effective
natural enemy of the scale. Early in
1887 Crawford wrote to Riley that I.
purchasi in Adelaide was
destroyed by a dipterous parasitoid and sent drawings of the fly and also
specimens which the U. S. Department of Agriculture received in February
1887. At first Riley doubted its
parasitic status, because no true dipterous fly parasitoids of scale insects
were then known. Later he became
convinced of its importance and this became the main objective in Koebele's
exploration trip to Australia. Riley
also recommended in 1886 that the natural enemies of the cottony-cushion
scale be investigated in Australia and introduced into California. The same year the California Fruit
Growers' Convention petitioned Congress to appropriate funds for the USDA to
do the work. However, Congress
refused and maintained that USDA funds could not be spent in foreign travel. The California
Fruit Growers' Convention invited Riley in April 1887 to provide a remedy for
the cottony-cushion scale epizootic, where he stated his belief that the
scale came from Australia where it was harmless and probably not from New
Zealand where it was recorded as a serious pest. He assumed that parasitoids regulated the scale at low
densities in Australia and again recommended that they be investigated and
imported into California. He offered
to send an entomologist to do this but that the US Congress would consider
the idea absurd. Thus he asked that
the State of California or Los Angeles County appropriate a few thousand
dollars to import the natural enemies.
Although the Convention again adopted a resolution in favor of sending
someone to Australia for natural enemies, no funds were generated from California. Around that time,
the California State Inspector of Fruit Pests, W. G. Klee,
corresponded with W. M. Maskell <PHOTO> in Auckland, New Zealand (Maskell had described the
scale as a new species from Auckland in 1978) and with Frazer Crawford in
Adelaide, Australia. Maskell told
Klee positively that Australia was the native home (letter was published in
the Pacific Rural Press, May 7, 1887).
Subsequently Riley, who meanwhile had reconsidered where the country
of origin might be and was suggesting Mauritius (letter to Pacific Rural Press,
June 4, 1887), agreed that Australia was probably the native home (letter in Pacific Rural Press,
March 4, 1888). As a result of
Klee's correspondence, Frazer Crawford with considerable effort
collected and sent some live Cryptochaetum
to Klee who liberated the flies on cottony-cushion scale in San Mateo County
near San Francisco in early 1888 before Koebele sailed for
Australia--ostensibly to get the same flies (DeBach 1974). This probably resulted in Cryptochaetum's establishment
because it eventually became common in California and there is doubt that
Koebele's later shipments to Los Angeles did survive after release. Financing for
Koebele's trip to Australia was through some skillful political
maneuvering. In 1888 an International
Exposition was to be held in Melbourne, Australia, and a US exhibit was
planned through the U.S. State Department.
Through the efforts of Riley, N. J.
Coleman, The California Commissioner of Agriculture and others, the U. S.
Secretary of State was persuaded to allocate $2,000 to pay the travel
expenses of an e4ntomologist who was to represent the U. S. State Department
at the Exposition. Riley selected
Albert Koebele, his assistant, who sailed from San Francisco on August 25,
1888. Koebele experienced
few of the problems in Australia that plagued some of the later foreign
explorers. As an official
representative of the U.S. State Department and the U. S. Department of
Agriculture, he received utmost cooperation and was accompanied by
knowledgeable local entomologists or growers, who often led him to known
pockets of the otherwise rare cottony-cushion scale. He was also furnished with free passes by
the State railways in Australia.
After he arrived in Sydney on September 20, 1888, Koebele searched for
four days and found only a few Icerya
and no natural enemies. The local
orange growers had no knowledge of the scale. Proceeding to Melbourne by train, he searched for some six days
but found no Icerya. He then went to Adelaide with a letter of
introduction to Frazer Crawford, and the next day in gardens in Adelaide Icerya was found, with the very
first scale examined containing nine pupae of Cryptochaetum iceryae. Nearly all the scales examined in Adelaide
were parasitized. While collecting
scales for shipment to California with Crawford in a North Adelaide garden on
October 15th, Koebele related on July 1889
(after his return to California), "I discovered there, for the
first time, feeding upon a large female Icerya, the Lady-bird, which will
become famed in the United States--Vedalia
cardinalis." <PHOTO>. By this time
the beetle was showing its potential in California. Koebele had written to Riley about his discovery and Riley
replied that he thought that Cryptochaetum
was probably the most promising, but to try others as well. Koebele then went
to Mannum in the Murray River valley, where much of today's oranges are
grown. There he found the scale being
parasitized by Cryptochaetum,
the Rodolia (= Vedalia, = Novius) cardinalis
Mulsant and a predatory green lacewing.
He returned within a week to Adelaide with material that was placed in
a cool cellar to await shipment to California. On October 24-25 he collected more scales in North Adelaide,
along with many parasitic flies and green lacewings. He described his first shipment as: "I finished
collecting for my first shipment on the 25th and estimated that I had about
6000 Icerya, which in return would produce at an average about four parasites
[Lestophonus = Cryptochaetum]
each. They were packed partly in
wooden and partly in tin boxes. Small
branches generally full of scales were cut so as to fit exactly lengthwise
into the box. With these the boxes
were filled and all loose scales placed in between, plenty of space remaining
for any of the insects within to move about freely without danger of being crushed
by loose sticks. Salicylic acid was
used in small quantities in the tin boxes to prevent mold, yet these, as I
have been informed by Mr. Coquillett, arrived in a more or less moldy
condition, while those in wooden boxes always arrived safe. In addition, Dr. Schomburgh, director of
the botanical gardens at Adelaide, kindly fitted up for me a Wardian case
which was filled with living plants of orange and Pittosporum in pots.
Large numbers of Icerya were placed in this, and such larvae as were
found feeding upon them...The object of this was to have the Lestophonus go on breeding
within the case during the voyage. No
doubt many infested scales arrived in Los Angeles." "I found
[later] on examining the tree [in Los Angeles], on April 12, 1889, under
which this case had been placed with a tent over it, that from several of the
Iceryas the Lestophonus had
issued. This case, as Mr. Coquillett
informed me in a letter of November 30, arrived in good condition, except
that the putty had been knocked off in several places, leaving holes large
enough for the parasites to escape.
Before opening the case he found two coccinellid larvae crawling on
the outside, and these when placed with the Icerya attacked it at once. He further said that there were only about
half a dozen living Chrysopa
adults. This would show that the
Lestophonus was still issuing on arrival in California and all turned out
more favorably than I had anticipated on seeing the box handled in such a
rough manner by the steamer hands at Sydney, to which point I accompanied this
as well as all the subsequent shipments.
I expected little good would come out of this method of sending and
therefore concluded to send only small parcels on ice thereafter, as had been
partly done at first. If once the
insects could be placed in good condition in the ice-house on the steamer
just before leaving, where a temperature of 38° Fah. at first and about 46°
Fah. on arrival in San Francisco existed, they must arrive safely. To accomplish this, the parasites with
their hosts were all collected the last three days before leaving Adelaide,
and on arriving home were immediately placed in a cool cellar. On the trip from Adelaide to Sydney, which
takes two days by train, y insects came generally in an ice-box on the
sleeping-car." Koebele then
surveyed other areas in Victoria and New South Wales but concluded that the
Adelaide area was best, so returned on November 8, 1888. After collecting about 6,000 scales in
five days and making a trip to Melbourne for additional material, he left
Adelaide for Sydney with the second shipment. He writes: "On the 26th I
left Adelaide on my way to Sydney, with what I considered even a better
shipment than the first.
Unfortunately this lot arrived in a bad condition at San Francisco,
owing to a gale on the route when the parcels fell off the shelving in the
ice-house, in which they had been placed, and most of them were crushed by
cakes of ice falling on them." Koebele made a
third shipment in late December and then travelled to Brisbane, where he
found only a few specimens of Icerya
and slowly returned to Melbourne with very poor collecting along the
way. At Melbourne he collected Cryptochaetum on a related
scale, Monophloebus sp. He then collected Icerya with parasitoids and about 200 Rodolia cardinalis
in the Sydney Town Hall garden, being now either more proficient at
collecting or luckier than during his first trip to Sydney. Under instructions from Riley to study Icerya in New Zealand on his
way home, he boarded ship on January 13, 1889 with his insects in the cold
room, and arrived in Auckland, New Zealand on January 28th. The scales with parasitoids and Rodolia beetles were found to
be in excellent condition at Auckland and were repacked in wooden boxes with
fresh Icerya found in Auckland,
and apparently were sent on to California.
He found no natural enemies in Auckland; however at Napier he found
large numbers of Rodolia cardinalis feeding on Icerya. According to Koebele this predator had
arrived in Auckland by chance, where Icerya
was destroying host plants five years previously, and there it cleaned nearly
the whole district around Auckland within about two years. At the time of Koebele's visit the
predator was dispersing into new areas, hence his big collection of about
6,000 specimens of Rodolia cardinalis at Napier. Returning to Auckland, these were placed
in the ship's cool-room at 4° C (38° F).
He left Auckland on February 25th and arrived in San Francisco,
Saturday evening March 16th, 1889.
The material could not be sent to Coquillett at Los Angeles until the
following Monday and he received it on March 20th, 34 days since collection
and 29 days on ice. Yet this arrived
in better condition than any previous shipment. The specimens were liberated under the same caged tree in Los
Angeles that had received the earlier specimens, which was on the property of
F. W. Wolfskill.
According to Coquillett's records, 129 living Rodolia cardinalis
were liberated through January 24, 1889.
On February 21, 35 Rodolia
arrived and were colonized on the property of J. R.
Dobbins in San Gabriel. The final
shipment of 350 live Rodolia
that was brought personally by Koebele on the ship was colonized on March 20,
1889. About one-third went to the
Dobbin's grove and the remainder to the large A. S.
Chapman grove in the San Gabriel valley. Altogether there
were about 12,000 living Cryptochaetum
iceryae received from
Koebele, which were all put under one caged tree. When the tree was examined on April 12, 1889 he noted that very
few Cryptochaetum remained
of the vast numbers of flies received.
Rodolia cardinalis had
killed nearly all the Icerya
at the Wolfskill tree by early April 1889.
Therefore, one side of the cage was removed and the beetles were allowed
to move to adjoining trees. On April
12, Coquillett began sending colonies to other parts of the State. By June 12, two months after the cage was
opened, 10,555 Rodolia cardinalis had been distributed
to 208 different growers and successful colonization occurred in nearly every
case. Within six months of the first
release of 28 beetles and with a total release of only 129, the original
trees in Wolfskill's orchard were virtually Icerya-free and the beetles had spread to a distance of
3/4 mile. In his Annual Report for
1889 Riley stated that in the original orchard (Wolfskill) practically all
the scales were killed before August 1889 and further that by the end of 1889
Icerya was no longer a
factor to be considered in citrus growing in California. Coquillett wrote in 1889 regarding the San
Gabriel colonization of February and March: "All of these
colonies have thrived exceedingly well.
During a recent visit to each of these groves I found the lady-birds
on trees fully one-eighth of a mile from those on which the original colonies
were placed, having thus distributed themselves of their own accord. The trees I colonized them on in the grove
of Dobbins were quite large and were thickly infested with the Iceryas, but at the time of my
recent visit scarcely a living Icerya
could be found on these and on several adjacent trees, while the dead and dry
bodies of the Iceryas still
clinging to the trees by the beaks, indicated how thickly the trees had been
infested with these pests, and how thoroughly the industrious lady-birds had
done their work." J. R.
Dobbins reported on July 1889, only four months after the first beetles were
released: "The vedalia
has multiplied in numbers and spread so rapidly that every one of my 3200
orchard trees is literally swarming with them. All of my ornamental trees, shrubs, and vines that were
infested with white scale, are practically cleansed by this wonderful
parasite. About one month since I
made a public statement that my orchard would be free from Icerya by November 1 [1889],
but the work has gone on with such amazing speed and thoroughness that I am
today confident that the pest will have been exterminated from my trees by
the middle of August. People are
coming here daily, and by placing infested branches upon the ground beneath
my trees for two hours, can secure colonizes of thousands of the vedalias,
which are there in countless numbers seeking food. Over 50000 have been taken away to other orchards during the
past week, and there are millions still remaining, and I have distributed a
total of 63000 since June 1." The Dobbins orchard
was so completely free of Icerya
that on July 31 he posted a notice that he had no more beetles for
distribution. The other colonized
grove in San Gabriel was similarly cleaned of scale (DeBach 1974). In 1888 A. S. Chapman stated that he was
being forced to abandon citrus growing on account of scales, while in October
1889 he stated that Rodolia
had cleaned up the scale on 150 acres.
In just one year shipments of oranges from Los Angeles County
increased dramatically from 700 to 2,000 freight train car lost. Riley in
1893 (DeBach 1974) published the following: "Mr. William F. Channing, of Pasadena, one of the eminent
Unitarian divine, wrote two years later [in 1891]: We owe to the Agricultural
Department the rescue of our orange culture by the importation of the
Australian lady-bird, Vedalia
cardinalis." "The white
scales were incrusting our orange trees with a hideous leprosy. They spread with wonderful rapidity and
would have made citrus growth on the whole North American continent
impossible within a few years. It
took the Vedalia, where introduced, only a few weeks absolutely to clean out
the white scale. The deliverance was
more like a miracle than anything I have ever seen. In the spring of 1889 I had abandoned my young Washington navel
orange trees as irrecoverable. Those
same trees bore from two to three boxes of oranges apiece at the end of the
season (or winter and spring of 1890).
The consequence of the deliverance is that many hundreds of thousands
of orange trees (navels almost exclusively) have been set out in southern
California this last spring." Out of a total
original stock of 514 beetles colonized from the end of November 1888 to late
March 1889 the rapidity and extent of this control was nearly unbelievable
(DeBach 1974). Coquillett in a letter
to Riley, October 21, 1889, summarized it as follows: "The first
half of the year I devoted nearly the whole of my time to propagating and
distributing the Australia Lady-bird (Vedalia
cardinalis) recently
introduced by this Division. At the
present time it is very difficult to find a living Fluted Scale (Icerya purchasi Maskell) in the vicinity of this city [Los Angeles],
so thoroughly has the Lady-bird done its work; and, indeed, the same is true
of nearly the entire southern part of the state, as well as of many
localities in the northern part." DeBach (1974)
reported that by 1890 all infestations in the State had been completely
decimated. The cost, aside from
Koebele's and Coquillett's salaries, was about $1,500.00; and all told less
than $5,000.00. Benefits to the
citrus industry of California have amounted to millions of dollars annually
ever since and as an aftermath similar successes have been attained over the
years in more than fifty countries around the world by transfer of Rodolia cardinalis and to a lesser extent of Cryptochaetum iceryae. Albert Koebele immediately became famous
and continued as a foreign explorer for the USDA and later for Hawaii,
although he never again achieved such a spectacular success. In California special funds were raised
and Koebele was presented with a gold watch and his wife with a pair of
diamond earrings. DeBach (1974) relates that as a sequel to
this story, Cryptochaetum iceryae had been increasing in
California and eventually became dominant in coastal areas, which includes
Los Angeles where Rodolia
attained its first notoriety.
Research since has shown that Cryptochaetum
alone would have done just as spectacular a control in the citrus areas of
1890 as did Rodolia. However, with expansion of citrus to
hotter, drier interior areas of California, Rodolia is the most important biological control factor. Kennett et al
(1999) mention the importation of another coccinellid, Rodolia koebelei (Horn), which was
introduced from Australia in 1892.
Although it became established and persisted for a number of years, it
was eventually displaced by R.
cardinalis. Later studies in
southern California by Quezada, <PHOTO>, (Quezada & DeBach 1973) revealed that Rodolia cardinalis and Cryptochaetum
iceryae impacted their host
in concert, with Rodolia tending
to displace Cryptochaetum in
arid areas, the reverse being true along coastal areas while in intermediate
areas both tended to be commonly present, depending on environmental
fluctuations. Greathead (1976)
reported that in colder climates Rodolia
is frequently eliminated during winter and recolonization is necessary to
maintain control. Cryptochaetum has a more
restrictive range of adaptability and has not been successfully introduced to
as many areas as Rodolia. For greater detail
on the various aspects of this biological control effort please refer to the
following references (Riley 1887, Coquillet 1889, Marchal 1908, Savastano
1919, Kuwana 1922, Autuori 1928, Gomez-Clemente 1929, Poutiers 1930, Thorpe
1930, Essig 1931, Leonard 1932, Bazduireva 1933, Bodenheimer 1933,
Bodenheimer & Tenenbaum 1934, Wolcott & Sein 1933, Chen 1934,
Stepanov 1935, Wille 1935, 1941; Ramachandra Rao & Cherian 1944, Geier
& Baggiolina 1950, Pruthi 1950, Subramaniam 1954, 1955; Bartlett & Lagace
1960). REFERENCES: [Additional references may be found at: MELVYL
Library ] Anonymous.
1917. Investigations on the
coccinellid, vedalia, and the scale-insect Icerya. Dept.
Agric. & Com. Plant Path. & Injur. Insects Bull. 3: 107 p. (Abs. in REv. Appl. Ent. (A),
6: 282). Autuori, M.
1928. Syneura infraposita
Borgm.-Schmitz (Diptera: Phoridae) um novo parasita da Icerya purchasi
Mask. Inst. Biol., Sao Paulo, Arch
1: 193-200. [in Portuguese w/ English summary]. Balachowsky,
A. 1932. Observations biologique sur l'adaptation de Novius cardinalis Muls. aux depens de Gueriniella serratulae
F. (Contribution a l'etude des coccides de france; 6 note). Rev. Pathol. Veg. Ent. Agric. Fr. 19: 11-17. Bartlett, B. R. 1978. Coccidae. In: C. P. Clausen (ed.), Introduced Parasites
and Predators of Arthropod Pests and Weeds.
U. S. Dept. Agric. Agric. Handbk. No. 480, Washington, D.C. 545 p. Bartlett, B. R.
& C. F. Lagace. 1960.
Interference with biological control of cottony-cushion scale by
insecticides and attempts to reestablish a favorable natural balance. J. Econ. Ent. 53: 1055-58. Bazduireva,
V. I. 1933. The fluted scale (Icerya purchasi Mask.) and its control. A review of literature.
Plant Protect. (Leningrad) (1932) 3:
35-64. [in Russian]. Bodenheimer,
F. S. 1933. Icerya purchasi Mask. and Novius
cardinalis Muls. Ztschr. f. angew. Ent. 19: 514-43. Bodenheimer,
F. S. & B. Tenenbaum. 1934. Icerya purchasi Mask. and its control in Palestine. Hadar:
32-4. Chen, F.
1934. Notes on two
coccinellids of Hwang-Yeh, Chekiang.
Ent. & Phytopath 2: 142-48.
[in Chinese]. Clausen, C.
P. 1978a. Biological control
of citrus insects. Chapter 6, Vol. IV.
In: The Citrus Industry. Univ. of Calif. Div. Agric. Sci.,
Berkeley, Calif. 362 p. Coquillet,
D. W. 1889. The imported
Australian lady-bird. Insect Life
2: 70-4. DeBach, P.
1964. Successes, trends and
future possibilities. In: P. DeBach (ed.), Biological Control of Insect Pests and
Weeds. Reinhold Publ. Co., New
York. 844 p. DeBach,
P. 1974. Biological Control
by Natural Enemies. Cambridge Univ.
Press. 323 p. Doutt, R. L.
1958. Vice, virtue and the
vedalia. Bull. Ent. Soc. Amer.
4: 119-23. Doutt, R. L.
1964. The historical
development of biological control.
Chapter 2, In: P. DeBach (ed.), Biological Control of
Insect Pests and Weeds. Reinhold
Publ. Co., New York. 844 p. Essig, E.
O. 1931. A History of Entomology. MacMillan Co., New York. 1029 p. Geier, P.
& M. Baggiolini. 1950. Quelques observationes sur la biologie de Pericerya purchasi Mask. au Tessin (Homop., Margaroid.). Schweitz. Ent. Gesell. Mitt.
23: 104-16. Gomez-Clemente,
F. 1929. La lucha natural. Estudio acerca de la Icerya purchasi
Mask. y de su parásito el Novius
cardinalis Muls. Estac. Fitopatol. Agric. Valencia. 53p. Greathead, D. J. 1976. A review of
biological control in western and southern Europe. Tech. Comm. No. 7, CIBC.
Commonw. Agr. Bur., Farnham Royal, Slough, England. 182 p. Kennett, C. E., J. A. McMurtry & J. W.
Beardsley. 1999. Biological control in subtropical and
tropical crops. In: Bellows, T. S. & T. W. Fisher (eds.), Handbook of Biological Control: Principles and Applications. Academic Press, San Diego, New York. 1046 p Koebele,
A. 1890. Report of a trip to
Australia to investigate the natural enemies of the fluted scale. U. S. Dept. Agric., Bur. Ent. Bull.
21: 1-32. Kuwana, I.
1922. Studies on Japanese Monophelebinae. Contrib. II. the genus Icerya. Japan Dept. Agric. & Com., Imp. Plant
Quart. Sta. Bull. 2. 43 p. Leonard, M. D.
1932. The cottony cushion
scale in Puerto Rico. J. Econ.
Ent. 25: 1103-07. Marchal, P.
1908. The utilization of
auxiliary entomophagous insects in the struggle against insects injurious to
agriculture. Pop. Sci. Monthly
(Apr.): 352-419. Poutiers,
R. 1930. Sur le comportemente du Novius
cardinalis (Coleoptera,
Coccinellidae) vis-a-vis de certains alcaloides. Soc. de Biol. (Paris)
Compt. Rend. 103, 1023-25. Pruthi, H. S.
1950. A foreign insect menace
to Indian citrus industry checked.
Indian Farming 11: 5-6. Quayle, H. J.
1938. Insects of Citrus and
Other Subtropical Fruits. Comstock Publishing
Co., Ithaca, New York. 583 p. Quezada, J.
R. & P. DeBach. 1973.
Bioecological and population studies of the cottony-cushion scale, Icerya purchasi Mask. and its natural enemies, Rodolia cardinalis Mul. Cryptochaetum
iceryae Will., in southern
California. Hilgardia 41: 631-88. Ramachandra Rao, R. S. Y. & M. C.
Cherian. 1944. The fluted scale, Icerya purchasi
Mask., as a pest of wattle in south India, and its control by the biological
method. Madras
Agric. J. 32: 20. Riley, C.
V. 1887. The Icerya or fluted scale,
otherwise known as the cotton cushion scale.
U. S. Dept. Agric., Div. Ent. Bull. 15. 40 p. Riley, C. V.
1893. Parasitic and predaceous
insects in applied entomology. Insect
Life 6: 130-41. Savastano, L.
1919. La ginestra etnea e la
cumune, l'Iceria e il Novius. Acireale R. Staz. Sper. di agrumic. e Fruttic. 37:
1-4. Smith, H. S. & H. Compere. 1916.
Observations on the Lestophonus,
a dipterous parasite of the cottony cushion scale. Bull. Calif. Dept. Agric. 5:
384-90. Stepanov, E. M. 1935. The biological
method of controlling pests of plants in Abkhazia. [Abs. in REv. Appl. Ent. (A), 24:
674). Subramanium,
T. V. 1955. Control of the
fluted scale in peninsular India.
Indian J. Ent. 16: 391-415. Subramanium, T. V. 1955. Control of the
fluted scale in peninsular India.
Indian J. Ent. 17: 103-20. Thorpe, W. H.
1930. The biology,
post-embryonic development, and economic importance of Cryptochaetum iceryae
(Diptera, Agromyzidae) parasitic on Icerya
purchasi (Coccidae,
Monophlebini). Zool. Soc. London
Proc. 60: 929-71. Wille, J.
E. 1935. Icerya purchasi y Novius cardinalis. (Peru) Min. de Fomento, Dir. Agric. y
Ganad. Informe 32. 23 p. Wille, J.
E. 1941. Resçmen de los diferences labores ejecutadas en el Peru para
combatir insectos daninos por el "método biológico." 6th Pacific Sci. Cong. Proc (1939) 4: 369-71. Wolcott, G. N. & F. Sein, Jr. 1933.
A year's experience with the cottony cushion scale in Puerto
Rico. Puerto Rico Dept. Agric. J. 17:
199-21. |
