Florida Agricultural Experiment Station


 The 1923-24 citrus crop of 20,000,000 boxes graded about as
follows: Bright and fancy, 20 percent or 4,000,000 boxes; golden,
45 percent or 9,000,000 boxes; russet, 35 percent or 7,000,000
boxes. In a survey of 32 representative packinghouses through-
out six of the leading citrus producing counties, made by the
junior author, it was found that 59 percent of the golden and
61 percent of the russet fruit were due to melanose. Assuming
that this condition represents the average for the state, it was
estimated that, with golden selling at a handicap of 30 cents
per box and russets and plains bringing 70 cents a box less than
brights, melanose losses for that year were about as follows:-
 In golden fruit, 5,310,000 boxes at 30 cents ............$ 1,593,000
 In russet fruit, 4,270,000 boxes at 70 cents .-................. 2,989,000
 Invested in spraying and pruning for melanose control 318,000
 Off sizes and cull fruit ...... .......... ...... .......................... 100,000
 Approximate loss due to melanose .................................. 5,000,000
 All commercial varieties of Citrus grown in Florida are at-
tacked by melanose but grapefruit appear more susceptible than
oranges. Melanose is rarely important in young groves but
ordinarily increases progressively with the advancing age of
the trees. In general, those conditions which promote the ac-
cumulation of dead wood may be considered predisposing fac-
tors to melanose development.
 SYMPTOMS OF MELANOSE
 Melanose affects the foliage, twigs and fruit of citrus trees,
attacking these parts only while they are sufficiently young to
be susceptible to infection.
 On the Leaves:-Melanose first appears on the tender young
leaves as minute, dark, circular depressions with yellowish mar-
gins (Fig. 1). As the leaves harden, the spots become flush with
the surface and later become distinctly raised, with somewhat
irregular margins. They are then rough and mahogany brown
in colnr and the discolorations in advance of them are no longer
evident (Fig. 2). If the infection is severe, the leaf partially
loses its natural green color and becomes pale green or yellow-
ish-green. The lesions occur on both surfaces but are most num-
erous on the upper. The markings quite often assume cir-
cular or ring-like patterns varying in diameter from one-eighth
to one-fourth inch. In case of severe infection, solid scar tissue
of various forms may result. The foliage on the watersprouts