GRAPES AND OTHER SMALL FRUITS 21 



rain and does not reach a maximum until the fourth or fifth. If after 

 a heavy rain there is dry weather for a week or more, the last traces of 

 leather rot, in the field, may be expected to disappear by the seventh 

 or eighth day. 



CONTROL MEASURES 



If shipments are precooled to a temperature between 35° and 40° F. 

 and kept below 40° in transit there is very little danger that leather 

 rot will cause appreciable loss during the ordinary transit time from 

 southern shipping points to northern markets. 



Observations made in Louisiana and Arkansas indicate that the rot 

 can be controlled fairly well in the field by mulching, which keeps the 

 berries from coming in contact with the soil (11, 30, 31). 



RHIZOCTONIA ROT 



(Rhizoctonia spp.) 



OCCURRENCE, SYMPTOMS, AND EFFECTS 



Rhizoctonia rot is known to occur in central Florida, North Carolina, 

 Tennessee, and Arkansas. In rainy seasons strawberries from all these 

 districts show this rot on the market, sometimes in such percentage 

 that their market value is seriously reduced. All varieties grown 

 where the rot occurs are susceptible. 



Affected berries are usually one-sided and show a hard brown 

 decayed spot to which small quantities of soil often adhere. Infection 

 begins on the under side where the berry touches the soil, usually 

 before it begins to turn red and sometimes before it is a third grown. 

 Early infection results in deformed fruits, but since the rot develops 

 slowly there may be no sign of it on the upper side of the berry. As a 

 consequence it is difficult to keep affected fruit out of the pack (pi. 9, 



Because of the slowness with which the rot develops there is little 

 clanger that it will spread from diseased to healthy fruit under good 

 refrigeration (fruit temperature below 45° F.) in transit. 



CAUSAL FACTORS 



The rot is caused by an unidentified species of Rhizoctonia, a soil 

 fimgus, which is the cause of disease in a number of other plants. 

 A study of artificially inoculated strawberries shows that infection takes 

 place in the small pits in which the seeds (akenes) are embedded ; it is 

 not known whether the hyphae can penetrate the uninjured epidermis 

 or are dependent on breaks in it for a way of entrance. 



CONTROL MEASURES 



Mulching with pine needles or straw is probably the best means 

 of controlling this disease (8,11,17, 37, 38). 



RHIZOPU8 ROT 



(Rhizopus nigricans Ehrenb. ex Fr.) 



OCCURRENCE, SYMPTOMS, AND EFFECTS 



The fungus Rhizopus has a wide distribution in nature and attacks 

 many kinds of fruit. It is of most importance on berries, grapes, and 



