Group Title: Press bulletin
Title: Russeting of citrus fruits
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 Material Information
Title: Russeting of citrus fruits
Alternate Title: Press bulletin 117 ; Florida Agricultural Experiment Station
Physical Description: 2 leaves : ; 21 cm.
Language: English
Creator: Rolfs, P. H ( Peter Henry ), 1865-1944
University of Florida -- Agricultural Experiment Station
Publisher: Florida Agricultural Experiment Station
Place of Publication: Gainesville, Fla.
Publication Date: May 1, 1909
Subject: Citrus -- Diseases and pests -- Florida   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
non-fiction   ( marcgt )
Statement of Responsibility: by P.H. Rolfs.
General Note: Caption title.
General Note: "May 1, 1909."
 Record Information
Bibliographic ID: UF00090479
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 - 78123161

Full Text


Florida Agricullural Experiment station.

Usually the rust mite does not occur in a grove later than the middle
of July. Last year, however, it continued to work vigorously late in the
fall, and in some groves as late as into January, causing bright fruit to
russet even after it had become ripe. Last spring was also exceptional in
regard to the activities of this little pest. Ordinarily it need give us no
concern before the middle of May. Many of us, however, were unpleasantly
surprised to find that the crop of fruit had been greatly damaged by it
before the first of May.
The rust mit' is the smallest animal belonging to the spider-mite family.
A single individual cannot be seen by the ordinary eye. Nearly every one,
however, can detect rust mites by the unaided eye when they occur in
countless numbers on citrus fruits, as they are likely to do some time
during May. They may be detected on the fruit by a very delicate light
coloring, as if the fruit had been dusted from a roadside. When this incon-
spicuous dusty appearance occurs, one should use the hand lens to determine
whether this condition is due to dust which has arisen from the soil, or
whether it is due to myriads of rust mites on the fruit. If it is found
that the rust mite is present, this is a signal for immediate action.
The rust mite, like other spider mites, is extremely sensitive to sul-
phur compounds; consequently we have a cheap remedy in almost all kinds
of sulphur mixtures. The most effective, and at the same time, one of the
cheapest, is the sulphur spray, made of sulphur and caustic soda. The lime
and sulphur mixture is also very effective. Only two .quarts of these sul-
phur solutions are usually needed to forty or fifty gallons of water.
A less effective, though somewhat cheaper, method of treating rust mite
is by means of flowers of sulphur. This is a fine powder of brimstone, and
may be applied by a powder gun. Before the invention of these powder
guns, people treated citrus groves effectively by throwing handfuls of
powdered sulphur into the trees. A mixture of flowers of sulphur with
about three parts of air-slacked lime is a little more easily applied, and
sticks to the leaves better than the sulphur alone. By mixing the lime

May 1, 1909.

with the sulphur the workmen are able to see what parts of the trees have
been treated, and so to do the work more thoroughly.
The dry insecticides for rust mite have their disadvantages, however,
in that they should only be applied when the trees are moist with dew.
In a large grove this requires much night work, to which most laborers
Other forms of contact insecticide may be used more or less effectively,
but should be avoided unless one has in mind the double purpose of de-
stroying rust mite and scale insects at the same time.
A grove that is kept thoroughly irrigated is not apt to be badly affected
by rust mite, since these mites do not endure a moist atmosphere. It is,
however, not safe to rely upon an irrigating plant as a preventive of rus-&
seting of oranges.

State papers please copy.

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