Bulletin 229, Diseases of Citrus in Florida


tacks the tissues only while very young and tender, it is neces-
sary that the spraying be done early in the spring if the fruit
is to be protected.
 If scab is inclined to be severe it is advisable to make two ap-
 plications of bordeaux-oil emulsion. The first of these (3-3-50
 Bordeaux mixture plus 1 percent of oil as an emulsion), which
 should be made just before the growth starts in the spring, serves
 to cover the old scab lesions and thereby materially reduces scab
 infections. The second (3-3-50 bordeaux mixture plus 1/2 per-
 cent of oil as an emulsion), which should be made during the last
 of the bloom when at least two-thirds of the blossoms have fallen,
 serves to protect the young fruit against the disease. Generally,
 however, commercial control of the disease can be secured with
 but the former application. The second application will also
 serve to control early melanose.
 Where scab infection is not likely to be very heavy, where
 melanose is not a factor, and where it is desired to control red
 spider or rust mites on late fruit, liquid lime-sulphur should be
 used instead of bordeaux-oil emulsion, making the applications
 at the same time recommended for bordeaux-oil emulsion. The
 lime-sulphur solution should be diluted at the rate of 1 part to
 25 or 30 parts of water (3 to 4 gallons per 100) for use before
 the new growth starts and at the rate of 1 part to 40 parts of
 water (21/ gallons per 100) for use later, based on a concentra-
 tion of 320 Baum6. In years when there is an extensive set
 of grapefruit from June bloom, spraying for scab control should
 be profitable at that time.
 Scab may be controlled to a considerable extent by removing
the sources of infection not essential to commercial fruit pro-
duction. The scattered sour orange and rough lemon trees
which frequently occur in groves carry the disease and serve
as centers of infection. Such trees should either be removed
or worked over to commercial Citrus varieties. Sour orange
and rough lemon sprouts from the rootstocks of the grove trees
should be cut off whenever they appear.
 Seedbed and other nursery stock prior to budding can be
kept fairly free from scab, with considerable gain in size, by oc-
casional applications of bordeaux-oil emulsion. The frequency
of applications is dependent upon local and seasonal conditions.
It is especially important to keep the new flushes of growth
protected during periods of rainy weather.