20 BULLETIN 531, U. S. DEPARTMENT OF AGRICULTURE. 
portation or refrigeration facilities, but it is often induced by fungi, 
chiefly Rhizopus nigricans. 
Rhizopus causes the softening and rapid collapse of strawberries, 
accompanied by the escape of much juice. 
Berries though bearing the spores of Rhizopus when shipped may 
still, with proper handling and refrigeration in transit, reach the 
market in good condition. The fungus is not able to penetrate un- 
injured epidermis, but enters readily through wounds in either ma- 
ture or green berries. 
Rhizopus has not been found of primary importance as a cause of 
field rot, but usually develops in berries at some time after they 
are picked. 
The humidity of the air has no perceptible influence upon the rate 
at which Rhizopus nigricans rots strawberries. 
The growth of Rhizopus nigricans is very slow at 10° C. (50° F.) 
or below, but increases rapidly with the rise of temperature above 
that point. Therefore the proper cooling and refrigeration of the 
berries from the time the}' are picked until marketed will reduce the 
losses from this rot. 
Since the diversity of shipping practices does not always permit 
such complete refrigeration, the reduction of infection by means of 
sanitation and careful handling is important. 
The conditions at the packing houses are frequently unsanitary, 
affording favorable opportunities for the growth of Rhizopus, and 
bruising the fruit during handling allows infection to take place. 
The packing houses and tables should be kept clean. Injury to the 
fruit should be avoided by care in handling, or preferably, by the 
elimination of all unnecessary handling. 
Washing berries in water in which dirt has accumulated injures 
their shipping qualities. 
The temperature of the berries during the time between picking 
and shipping has an important influence upon the later development 
of rot. 
Drying washed berries, especially by exposure to sunlight, in- 
creases decay, because the subsequent exposure of the dry berries to 
prevailing high air temperatures favors the development of Rhi- 
zopus within their tissues. The higher shipping quality of fruit 
packed wet seems to be due to the facts that the temperature of the 
fruit is lowered by washing in cold water and that by prolonged 
evaporation the berries are kept cool for a considerable time, during 
which they may be hauled to the station and placed under refrig- 
eration. 
