FURTHER STUDIES OF THE ROTS OF STRAWBERRY FRUITS, 3 



(4), and others, and it is apparently of first importance in the straw- 

 berry/ 



IMPORTANCE OF LOW TEMPERATURE. 



The careful studies of Miss Ames (1) indicate the close relation 

 between temperature and the rate of growth of Rhizopus. Rhizopus 

 OTOWS very slowly at a temperature of 10° C. (50° F.). The rate of 

 growth increases very rapidly with the rise of temperature above that 

 point, however, so that the fungus will develop more in a short time 

 at a relatively high temperature than in a much longer time at a 

 lower temperature. Miss Ames found, for instance, that Rhizopus 

 nigricans would produce mature sporangia in 36 hours at a tempera- 

 ture of 33° C, while at temperatures oflO°tol2°C. three weeks were 

 required. 



The importance of low temperature in reducing rots of strawberries 

 was strikingly shown by tests conducted in connection with experi- 

 mental shipments between Monett, Mo., and St. Paul, Minn. Similar 

 boxes of strawberries of the Warfield variety were inoculated with 

 spores and mycelium of Rliizopus nigricans through needle wounds, 

 riie berries, at a uniform temperature of about 24° C. (75° F.), were 

 all placed in the cars about 6 p. m. 



Accurate temperature records kept by Mr, V. W. Ridley showed 

 bhat the most marked difference in the conditions to which the four 

 boxes referred to in Table I were subjected was in the time consumed 

 in reaching a temperature below 10° C. (50° F.). Examination of 

 the fruit four days later, on arrival at destination, showed that the 

 longer the time consumed in reaching 10° C, the greater the amount 

 of rot developed. The results are summarized in Table I.^ 



Table I. — Relation of temperature to the growth of Rhizopus in inoculated strawberries 

 of the Warfield variety, in connection with experimental shipments between Monett, Mo., 

 and St. Paul, Minn. 



Crate. 



Hours con- 

 sumed in 

 reaching 10° C. 

 (50° F.). 



Condition on examination after arrival at destination. 



No. A 



No.B 



No.C 



^fo. D 



40 

 30 



7 

 5 



Berries practically all rotten, most of them bearing aerial hyphse with im- 

 mature sporangia. 



All berries showmg a rotten area about one-fourth of an inch in diameter 

 around the inoculation. 



70 per cent of berries showing no indication of fungous growth, the remaining 

 30 per cent showing small rotten spots. 



91 per cent of berries showing no indication of fungous growth, the remaining 

 9 per cent showing very slight softening around the point of inoculation. 



Other boxes of inoculated fruit of the Warfield variety, as well as 

 3ome Aromas, were also included in this experiment. The results 



1 Mr. E. L. Markell, of the Bureau of Markets, informs the writers that his own investigations, conducted 

 luring 1915 and 1916 at Hammond, La., the results of which are as yet unpublished, clearly showed the 

 Importance of care in handling strawberries. 



2 See also Ridley, V. W. Factors in transportation of strawberries from the Ozark region. U. S. Dept. 

 Agr., Markets Doc. 8, 10 pp., 6 fig. 1918. 



