Grape Growing in Florida


proper spray materials are thoroughly applied at the correct
time, control is readily obtained.
 FRUIT DISEASES
 The most serious damage to the fruit is done by black rot,
bitter rot and ripe rot. Downy mildew is severe in some sea-
sons. Anthracnose would be of great importance if any vari-
eties high in vinifera blood were being grown. All of these
diseases are controlled by copper sprays according to the
schedule shown on page 34.
 Black rot caused by the fungus Guignardia bidivellii (Ell.)
V. & R., first makes its appearance on the leaves about the time
they have reached full size and before they have matured. It
is characterized by reddish-brown dead spots. With the aid of
a hand lens, black pustules containing the spores of the fungus
may be seen scattered on the upper side of these spots.
 The disease becomes apparent on the fruit when it is about
 half grown as a pale spot which soon turns brownish. Usually
 the discoloring soon involves the entire berries which turn black.
 Shortly after the spot becomes brown a shriveling of the berry
 takes place and, if it does not shell off, it takes on the character-
 istic mummied appearance so familiar in vineyards infected
 with black rot. The period elapsing from the first appearance
 of the spot until the mummied stage is usually six to 10 days.
 Depending upon the control measures used, this disease takes
 an annual toll of from 5 to 25 percent of the crop. Frequently,
 if no control is used, the loss of marketable fruit is 100 percent.
 Experiments by Loucks (7) have shown that bordeaux sprays
 applied at the blooming period are of the most importance in
 controlling black rot on the fruit. Applications put on at other
 times in the spray schedule are important, but those during
 the blooming period are imperative.
 Bitter rot, Melanconium fuligineum (Scrib & Vial.) Cav., and
 ripe rot, Glomerella cingulata (Atk.) Spauld. and Von Schrenk,
 are noticeable only on the fruit after it has begun to color for
 ripening. The berry attacked by either disease becomes soft
 and slightly shriveled. Minute pustules become evident and if
 conditions are favorable, myriads of black spores soon cover
 the berry. Considerable shelling is caused by these late rots,
 and they are of much importance because of the fact that they
 continue to develop on the fruit after it is packed. For this
 reason it is necessary to grade out carefully at packing time
 all fruit which shows any sign of these rots.