Citation
Miscellaneous papers

Material Information

Title:
Miscellaneous papers
Series Title:
Technical series / United States. Dept. of Agriculture. Bureau of Entomology ;
Added title page title:
Orange thrips
Added title page title:
New genus of Aleyrodidae, with remarks on Aleyrodes Nubifera Berger and Aleyrodes Citri Riley and Howard
Creator:
Sanders, J. G
Hine, James S ( James Stewart ), 1866-1930
Moulton, Dudley
Howard, L. O ( Leland Ossian ), 1857-1950
Quaintance, A. L ( Altus Lacy ), 1870-1958
Townsend, C. H. T
Davis, John J ( John June ), 1885-1965
Place of Publication:
Washington, D.C.
Publisher:
U.S. G.P.O.
Publication Date:
Language:
English
Physical Description:
x, 200 p., viii leaves of plates : ill. ; 22 cm.

Subjects

Subjects / Keywords:
Coccidae ( lcsh )
Horseflies ( lcsh )
Thrips -- California ( lcsh )
Aphelinidae ( lcsh )
Aleyrodidae ( lcsh )
Tachinidae ( lcsh )
Citrus thrips ( lcsh )
Aphids -- Speciation ( lcsh )
Insect pests ( lcsh )
Genre:
bibliography ( marcgt )
federal government publication ( marcgt )
non-fiction ( marcgt )

Notes

Bibliography:
Includes bibliographical references and index.
General Note:
Papers published separately, 1906-1909 with continuous paging.

Record Information

Source Institution:
University of Florida
Rights Management:
This item is a work of the U.S. federal government and not subject to copyright pursuant to 17 U.S.C. §105.
Resource Identifier:
029624052 ( ALEPH )
28237603 ( OCLC )
agr15001506 ( LCCN )
Classification:
632 ( ddc )

Full Text
LIBRARY
STATE PLAMF BOARD
TECHNICAL SERIES, No. 12, PART VI1.
U. S. DEPARTMENT OF AGRICULTURE,
JBTTREAUT 1 OF NTOMOIEOGPV.
L. 0. HOWARD, Entomologist and Chief of Bureau.



MISCELLANEOUS PAPERS.











By 1)IT)LEY M(8JJO
Engaged in D)eciduous Fi--it Insect Irnvest~gatwns.




ISSUED FEBRUARY 11, 1909.

















WASHINGTON:
GOVERNMENT PRINITINGU OFFICE.
19S






















C INTENTS.


Page.
Intro rd ............................................................. 1I19
D istribution -------------------------------------------------------------- 119
Extent and nature of injury ............................................... 119
Life history notes ------------------------------------------------------- 120
Soil conditions as affecting )revalence ---------------------------------- 120
Remedies -------------------------------------------------------------- 21
Enemy ---------------------------------------------------------------1 21
Description ------------------------------------------------------------- 121





I IIU ST RATIO NS.



PLATE.
page.
PLATE VIII. WNork of the orange thrips (Euthrips citri n. sp.). Fig. 1.Injury to tender orange shoot. Fig. 2.-Orange buds in axils of leaves killed back as fast as formed, preventing further growth. Fig. 3.-Scab injury at stem-end of orange, due to work of thrips shortly after blossoms fell.
Fig. 4.-Scab injury at distal end of orange, due to work
of thrips late in season -------------------------------120
II












U. S. D. A., B. E. Tech. Ser. 12, Pt. VII. Issued February 11. 1909.

MISCELLANEOUS PAPERS.


THE ORANGE THRIPS.
By DUDLEY MOULTON,
E)giged in Dciluous Fruit Io.Sct ln sti!i(tion-".

INTRODUCTORY.

The orange thrips, Euth)'ps citr, a new species, described in this article, has become a very important orange-tree pest in the southern San Joaquin Valley of California and has been the subject of special investigation. The writer has been able to talk with many orange growers and packers, and with men who have developed extensive nurseries, and the following notes have been gathered largely from these sources.
DISTRIBUTION.

The San Joaquin orange belt extends along the western border of the Sierra foothills from a point about east from the city of Fresno, southward to a. short distance below Porterville., with some orchards as far south as Bakersfield. The belt is not at all continuous, but is broken in many places because of improper soil conditions, frosts, and the lack of water for irrigation. The thrips is distributed everywhere throughout this belt, but is not found, so far as I have been able to learn, in any other orange section of California.
EXTENT AND NATURE OF INJURY.

The orange groves in the San Joaquin belt are wonderfully *profit,able, for as much as $2,000 per acre has been realized in a single year from full-bearing orchards. This thrips problem is, therefore, a very important one when we consider the large area which is planted and is being planted.
Curled and thickened leaves and marked oranges, the characteristic signs of the thrips, have been known for from ten to fifteen years, but only recently have these injuries been attributed to the thrips. The thrips has been increasing rapidly in numbers, until now the annual loss to the- orange growers amounts to many thousands of dollars.
119






120 MISCELLANEOUS PAPES.

The writer recently visited a packing house wh*' oranges. f m thrips-infested orchards were being graded and boxed, and found that about 30 per cent were passed from faicy (first grade) to choice (second grade), which means a difference in price of about 40ents per box; and that about 5 per cent of the rop was being passed out as culls, due entirely to the scablike markings of the thrips. While the quality of the fruit is not noticeably impaired, as the injury is present only on the surface often skin, ra s are graed ad also sold largely' on appearance, and thisab ces a very unpresentable fruit. (See Pl. VIII, 3 4.)
The thrips feeds also on ligand ner bnc a the
damage to these is serious, although t to niiaXyle as on 4he fruit. Only new ly unfolding and tender leaves and bus are attacked; as the feedin is mostly confined to the surface no part of the leaf tissue is killed outright, but there follows the silvering," characteristic of thrips and other surface-feeding insects. The leaves become cupshaped and wrinkled and the tissues noticeably thickened. (PL VI figs. 1, 2.) Orange trees in this section have four growths annual so that there is always an abundance of new foliage present when the thrips is above ground.
LIFE-HISTORY NOTES.

There are apparently two broods of this species. Adults of the first brood appear just before the blossoms in February, March, and April, and a second brood appears in July, August, September and October. Adults and larve of the first brood feed onthe small oranges just as the petals are being thrown off, the larvaeusually under the protection of the sepals, and on the first growths ofthe foliage. The second brood feeds on the nearly mature oranges and on the third and fourth growths of the foliage. All varieties of oranges and lemons are attacked, but the very noticeable scabbin on the fruit is common only on the navel orange; it is less conspicuous on the Valencia.

SOIL CONDITIONS AS AFFECTING PREVAIETCE.
It has been noticed that the thrips is not so prevalent on trees planted in sedimentary or loam soils as where the soil is of a claey or adobe texture. This fact may be explained as follows: This thrips, like most others of its group, presumably spends the last of its larval, its pupal, and its early adult life in the soil underneath the trees, and would naturally, then, be more or less affected by the texture offhe soil and by cultivation. Orange groves are usually irigate 'several times during the summer and are cultivated throughout the year. Sedimentary soils break to pieces readily







Tech. Series 12, Part VII, Bureau of Entomology, U. S. Dept. of Agriculture. PLATE VIII.














#4






















,i 2























4

3
WORK OF THE ORANGE THRIPS (EUTHRIPS CITRI, N. SP.).
Fig. 1.-Injury to tender orange shoot. Fig. 2.-Orange buds in axils of leaves killed back as fast as formed, preventing further growth. Fig. 3.-Scab injury at stem end of orange, due to work of thrips shortly after blossoms fell. Fig. 4.-Scab injury at distal end of orange,
due to work of thrips late in season. (Original.)






THE ORANGE THRIPS. 121

when thus moistehed and cultivated, and thrips in this ground would probably be broken from their small cells, if indeed they were able to make cel at all in this soil, and many of them would be killed by the cultivator and y the grinding together of the soil particles during cultivation. On the other hand, in clay lands the particles of soil pack closely.together and form clods, and during cultivation any, numhr'of thrips within these c s might be repeatedly turned
ovei t .witht Tr soil, too, it would be possible
for the' th Oto m ." .hrog, well-lined cell.
Another elti tion of orange groves should be mentioned tio After th trees have become large and
the44- s lang' ver and drag on the ground it seems
impossible t cultivate thor ughly close up to the tree, and there may be an tofseveral square feet that is not disturbed during the entire summer. This offers an ideal breeding place for the thrips.
REMEDIES.
WAe are not able at this tiine to say what spray can be used to control this thrips, but a strong tobacco extract will doubtless prove effective and will. not hurt the tree. Some of the cheaper soap washes ought also to be effective.
ENEMY.
It may be mentioned that a Triphleps, presumably T. insidiosus Say, is found everywhere feeding on the larvae of this thrips.
DESCRIPTION.
The following description of the female of F. citri has been made after examination of many specimens. No males have yet been collected. The insect is called citri because, so far as we know, it feeds on citrus trees only.
Euthrips citri n. sp.
Jeasurements: Head, length 0.75 mm. width 0.15 mm.; prothorax, length 0.09 mm., width 0.18 mm.; nmesothdrax, width 0.24 mm.; abdomen, width 0.25 mm.; total body, length 0.86 mm. Antenne: 1, 12 : 2, 36/; 3, 39/; 4, 39A; 5, 30/; 6, 34,; 7, 6/; 8, 121; total, 0.205 mm. Color, yellow to orange-brown, with thorax and segment 2 of antenna more noticeably orange-brown.
Head twice as wide as long, retracted considerably into the prothorax, broadly rounded in front, with only slight depressions to receive the basal joints of the antenne; two spines on anterior margin, other spines not conspicuous; cheeks almost straight and parallel. Eyes large, occupying almost one-half the length of the head,






122 MISCELLANEOUS PAPERS.

prominent; pigment deep red to purple; facets of eyes large, ey pilose. Ocelli subapproximate, margined inwardly with yello brown crescents. Mouth-coie short, reaching almost to poster margin of prothorax, broadly rounded and with black stop at ti maxillary palpi 3-segmented. Antennc 8-segmented, with segme 2 orange-yellow, other segments uniformly light brown; segment 2, 4, 5, 6 almost equal in length; style about one-half the length segment 6. All spines inconspicuous; sense cones trasparen
Prothorax about twice as wide as long, posterior, angles broad rounded; with long brown and outer small spine at each posteri angle, other spines not conspicuous. Mesothorax largest and wi anterior angles broadly rounded. Legs light yellow-brown, wi tarsi lighter but dark brown at the tips; spines on legs brow Wings present and fully developed, fore-wings broadest near b and pointed at tips; with a ring vein and a single longitudinal ve which divides at about one-third the length of the wing from t base, the anterior part running parallel and approximate to t anterior part of the ring vein and ending abruptly near the tip, t posterior paralleling and approaching the posterior part of the ri vein and ending about one-half the wing's length from the end, ea branch with a dark-brown marking immediately at its tip. The co bears a row of about 29 regularly placed spines. Other spines place as follows: A group of 5 near base of median longitudinal vein; 2o either side of where second vein branches from the first, and 3 se tered spines about equidistant on each branch vein and in each ca one of these spines immediately at the end of the vein; several rah long spines on scale. Veins of the fore-wing unusually strong a conspicuous, somewhat orange colored near base but fading to yel near tip. Membrane of wings transparent.
Abdomen ovoid, tip conical, all spines, exceptinga very few at t inconspicuous.
Described from many female specimens collected from oran foliage and fruit at Exeter, Tulare County, Cal.

0 UNIVERSITY OF FLORIDA

3 1262 09229 6390111




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