2 BULLETIN 686; U. S. DEPARTMENT OF AGRICULTURE. 



RHIZOPUS. 



TYPE OF ROT INDUCED. 



Among the numerous fungi which have been found growing on ripe 

 strawberries, Rhizopus, as pointed out in an earlier paper (12, p. 4) 

 is by far the most important. This fungus destroys strawberry 

 tissue more rapidly than any other yet found and causes the affected 

 fruits to collapse with the loss of much juice, producing the charac- 

 teristic "leak" which so frequently discolors strawberry boxes and 

 crates in the market. The spores of this fungus are apparently very 

 generally present on ripe strawberry fruits. 



A list of fruits and vegetables on which Rhizopus nigricans Ehrb. 

 has been reported was published by the writers (12, p. 9) . On June 1 , 

 1917, this fungus was observed fruiting abmidantly on red rasp- 

 berries (Ruhus sp.) and dewberries {Ruhus sp.) in the Chicago mar- 

 ket, and later (July 23) on blackberries in the Washington market. 

 In all these cases the fungus seemed to be producing the leak charac- 

 teristic of its action on strawberries and other fruits (12, p. 11). The 

 berries had settled to about one-half their original height in the box, 

 and the juice was leaking from the bottoms of the boxes or crates. 



It is of interest to note that in his studies of Rhizopus, Wormald 

 (14, p. 483) proved that both the so-called plus ( + ) and minus ( — ) 

 strains of this fmigus are able to produce the characteristic soft rot 

 of tomatoes (Lycopersicon esculentum) . 



It is probable that Rhizopus occurs as a fruit rot of tomatoes in 

 this country, although no reference to it can be found in available 

 literature. In a car of tomatoes from Cuba which was examined in 

 Boston in January, 1918, by Mr. C. E. Merrill, food products inspector 

 of the Bureau of Markets, and one of the writers, several instances 

 were found in which a species of Rhizopus was producing a soft rot 

 of tomatoes. 



IMPORTANCE OF CAREFUL HANDLING. 



Early in their investigations (10, p. 364) the writers became con- 

 vinced that Rhizopus rarely, if ever, enters strawberries through tb 

 uninjured epidermis. Continued observations and experiments ha^ , 

 confirmed this conclusion. As strawberries are very easily injur<r ' 

 they should be handled as little and as carefully as possible. S 

 ing, or at least some examination at the packing shed, is usually n 

 sary, but berries should be handled carefully in order to reduc 

 minimum injury and the consequent decay. Wlien practical ? 

 when most of the picking is done by the grower's family or ., jx 

 perienced help, the berries may be sorted as picked. This is piob ablv 

 the most desirable procedure. The importance of careful ' , 



as a means of reducing loss from decay in various fruits a 



clearly shown in several investigations by Ramsey (5 and A] 



