Group Title: Press bulletin
Title: Orange mites
Full Citation
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 Material Information
Title: Orange mites
Series Title: Press bulletin
Physical Description: 5 p. : ; 21 cm.
Language: English
Creator: Gossard, H. A ( Harry Arthur ), 1868-1925
University of Florida -- Agricultural Experiment Station
Publisher: Florida Agricultural Experiment Station
Place of Publication: Gainesville
Publication Date: 1902
Subject: Oranges -- Diseases and pests -- Florida   ( lcsh )
Spider mites -- Control -- Florida   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
non-fiction   ( marcgt )
Statement of Responsibility: by H.A. Gossard.
General Note: Caption title.
General Note: "May 10, 1902."
General Note: At head of title: Department of Entomology.
 Record Information
Bibliographic ID: UF00090450
Volume ID: VID00001
Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: oclc - 79958343

Full Text

Press Bulletin No. 24. (EMERGENCY) May 10, 1902.


Experiment Station.



The warm dry weather of the present spring has mul-
tiplied all forms of the family Tetranychidae to an ex-
cessive degree. Not since 1886 or 1889 have mites at-
tracted such attention in Florida or threatened such wide
spread damage as during the present season. During the
latter part of April reports began to pour in upon us ac-
companied by specimens of various Acarinidae and before
the first week in May had passed every quarter of the or-
ange growing districts had been heard from, the reports
indicating that the damage was great and that in some
districts there was great excitement.
Sincemore or less damage may continue for several
weeks before the rainy season opens we believe it best to

issue an emergency bulletin giving some account of the
history of these insects and especially of the remedies
that are most effective against them.
Perhaps the most important species is the six-spotted
mite, TETRANYCHUS SEXMACULATUS. This insect first
came into prominence as an orange enemy in 1886, just
after the severe freeze, the weakened condition of the
trees seeming to enable it to multiply excessively. It
disappeared in June with the beginning of the rainy sea-
son, reappearing the following spring in still greater num-
bers and inflicting severe damage but retiring as usual
with the commencement of the summer rains. In 1889
it again became something of a scourge and has appeared
in smaller numbers at various times since, but has not
been the occasion of general alarm until this spring.
scription of the insect is found in Insect Life, vol. 2,
page 225, and abbreviated somewhat and adopted to our
present purpose is as follows: Length of full grown
specimens 0.8mm, or about .012 of an inch. This is
slightly smaller than most members of its family. It is
of oval shape, being widest just back of the eyes. Gen-
eral color pale greenish yellow, the abdomen in mature
specimens being marked' with six or less small dusky
spots arranged in two lateral rows of three in each row on
the back. Most of the younger mites are without these
spots or have but part of them present. Some of the ma-
ture specimens have fewer than six spots and these are
often quite indistinct. Eyes, two on each side, the ante-
rior one of each pair being blood-red and the pigment so
disposed as to give the appearance of two red eyes on each

side; the posterior eyes are colorous and transparent. A
lateral constriction just back of the eyes divides the body
into two, more or less distinct, regions. The terminal
joint of the legs is longest. The thumb of the palpus is
quite stout and bears on its, tip three fingers, of which the
middle one is largest. The young mites have but three
pairs of feet. The eggs, which are globular in shape and
either colorless or of a pale greenish-yellow, are loosely
attached to the delicate web which may be found chiefly
along the under sides of the leaves. With warm dry
weather the life cycle from egg to adult is not more than
ten days.
The insects are carried from tree to tree upon the
feathers of birds, by becoming attached to the feet of
lady-bugs, upon fallen leaves driven before the wind, etc.
They can travel upon a leaf surface about two inches in
one minute or ten feet in an hour and therefore they
quickly spread from any point where they have become
newly established.
the leaves showing as streaks and spots along the midrib
on the upper surface of the leaves and as blotches of yel-
lowish rusty-brown on the lower sides indicates the in-
sects presence. The excrements show as minute black
spots and the cast skins,where aggregated together con-
stitute whitish silvery patches. After a few weeks the
leaves curl, shrivel, and fall, more than half of the leaves
often coming down and from one-third to two-thirds of
the immature fruit. In 1899 one grove located in Citra,
Fla., reported a crop of only about ten thousand boxes
from the heaviest bloom the grove had ever put forth,
whereas, it had yielded twenty-four thousand boxes the

preceding year, the whole shrinkage of product being at-
tributed to the six-spotted mite.
Two other species of Tetranychus are often present
with the six-spotted mite upon the same leaves, but as
the observations and remedies applicable to" the one spe-
cies may be used with all of them, from a practical
standpoint it is only necessary to mention the others.
The rainy season of June and July causes the mites
to practically disappear and they remain in such small
numbers during the latter part of the year that they are
rarely noticed at all. Vigorous trees, especially those
grown on high hammock land or low moist soil, are not
apt to be injured and where irrigation or artificial water-
ing is practiced damage is slight. Drenching the trees
with water from a hose where the water supply is abun-
dant, as -in the case of irrigated groves, meets every de-
REMEDIES.-The best specific against six-spotted mite
is some form of, sulphur. If flowers of sulphur are blown
upon the foliage with a blow-gni inl the early morning
while the due is yet on the leaves or just after a rain this
insect as well as the rust-mite will be held in check.
Probably as good a machine as any made and adapted- to
this kind of orchard use is the Champion Powder Gun,
manufactured by Leggett & Bro.,301 Pearl St., New
York. It may be had from the manufacturers or from al-
most any wholesale Seed or Nursery dealer such as Peter
Henderson & Co., New York. It will carry sulphur par-
ticles to the top of a twelve foot tree with ease in calm
air and by means of ladders the largest trees may be
thoroughly dusted. Dusting should be repeated every
ten days or two weeks until the mites disappear.
Perhaps more satisfactory than dusting with sulphur

is spraying with bi-sulphide of lime. Take 5 lbs. of sulphur
and 5 lbs. of lime, boil together in a few gallons of water until
everything is dissolved and a brownish liquid is obtained.
Dilute to one hundred gallons for use and spray every two or
three weeks if necessary. A whale oil soap mixture of sul-
phur is more persistent than the lime mixture and does not
need repeating so often. Take of whale-oil soap 7 lbs., one
quart of sulphur by measure, and boil with a few gallons of
water until dissolved, then dilute to forty gallons of spray.
While the eggs of the mites are not killed by any of these ap-
plications, the adherent sulphur particles kill the young mites
as fast as they are hatched.
Where neither powder-guns nor spray-pumps are at hand,
-and delay must be avoided, some relief will be afforded by
ascending the trees on ladders in the morning, while the dew
is on, or just after a raitn, and throwing flowers of sulphur'by
hand into the foliage. On tall trees, three or four handfuls
should be thrown from one setting of the ladder at intervals of
four or five feet from the base of the foliage to the top, and the
ladder should have four settings against the same tree-one at
each point of the compass. A slow fumigation seems to result
from such free use of sulphur by hand, putting marked check
upon the development of all forms of Acarinidae.


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