Florida Agricultural Experiment Station


in the management of tangerine groves since, when the limbs
loaded with fruit are bent down, the upper sides thus exposed to
the direct rays of the sun become scalded very readily.
 Sunscald of trunks and erect branches is apt to take place as
 readily, if not more so, in the winter months, when the sun's
 rays are more slanting, than in the summer when the sun is
 nearly overhead. This injury is most likely to occur on those
 parts on which the hot sun strikes longest between noon and
 mid-afternoon. Hence, it generally occurs on the southwest
 side of the trunk and on exposed limbs, especially when more or
 less horizontal. The direct rays of the sun either kill the bark
 down to the wood (Fig. 87) or they may merely kill or injure
 the cells of the outer portion of the bark, causing this part to
 dry up and scale off. It has been found that the bark of the
 trees may be heated many degrees above that of the surround-
 ing air by the rays of the sun. The resulting injury is often
 mistaken for the attack of certain parasitic diseases. The injury
 caused by sunscald, however, may render it possible for certain
 organisms to invade and kill the bark and intensify the injury.
 Wood-decaying organisms and wood-boring insects are especially
 likely to gain entrance through injuries arising from sunscald.

 CONTROL OF SUNSCALD
 Young trees may be protected from sunscald by shading or
 whitewashing and the trunks and branches of older trees should
 always be whitewashed when there is any danger from sunscald.
 A durable whitewash may be prepared according to the following
 formula:
 Hydrated lime .................................... 50 pounds
 Common table salt ....................... ....... 6 pounds
 M olasses .-.................... ................... 1 pint
 Powdered alum ..................................... 3 ounces
 Hot water .................................. ......... 10 gallons
 Dissolve the salt and alum in the water and add the molasses.
Pour this mixture on the lime and stir thoroughly. This wash
is somewhat brown in color but whitens after application. The
whitewash may be thinned with a little more water, if neces-
sary, and applied with a spray pump.
 Growers are advised not to wrap burlap sacks around trunks
to protect them from sunscald, since the sun shining on the
sacks after they have become wet by rain will scald the wrapped
trunks very readily.