Bulletin 229, Diseases of Citrus in Florida


tion of the home-made solutions will often vary from 22 to 28
degrees Baume. Such differences in density will make impor-
tant differences in the amount of water which should be added
to secure the proper strength of spray solution at given dilutions.
The density of lime-sulphur concentrates should therefore be
determined by a hydrometer with either the Baum6 or specific
gravity scales, preferably the former. This testing instrument,
which can be obtained from some of the firms that handle lime-
sulphur or spray supplies, will enable one to prepare accurately
spray solutions of lime-sulphur of a definite strength regard-
less of the variation in density of the concentrated solution.
 Table I gives the figures for diluting lime-sulphur solutions of
varying degrees of density. The first column gives the range
of hydrometer readings of the concentrated solutions for both
the Baum6 and specific gravity scales. The other columns give
the amounts of the concentrated solution to use in order to pre-
pare 50 gallon lots of spray solutions diluted to a range of
strengths varying from 1 to 8 to 1 to 65. Thus, if a concentrated
solution shows a Baum6 reading of 29 degrees and it is desired
to use this at a strength of 1 to 30, in the column under 1 to 30,
opposite 29 degrees, will be found 8 quarts. This indicates that
8 quarts of a solution of this concentration will be required to
make 50 gallons of spray solution of a 1 to 30 strength.

DISEASES CAUSED BY PARASITIC FUNGI AND BACTERIA
DISEASES ATTACKING TREES, PARTS OF TREES OR
 FRUIT BUT NOT CAUSING FRUIT DECAY
 MELANOSE
 Caused by Diaporthe (Phomopsis) citri (Fawcett) Wolf
 Melanose occurs throughout the citrus-growing sections of
Florida and the Gulf states and has been reported from most
of the other citrus-growing countries of the world. This disease
was first observed at Citra, Florida, in 1892, and was first de-
scribed and named by Swingle and Webber in 1896. Within
recent years, melanose has become widespread and prevalent
to the extent that, in the older citrus sections of Florida, it is
the most important cause for lowering the grade of the fruit.
In fact melanose, together with the Phomopsis type of stem-end
rot, impairs the market value of more citrus fruit than all other
parasitic diseases combined.