INTERNAL BROWNING OF YELLOW NEWTOWN APPLE. 23 



browning will develop in fruit from over the district as a whole, or 

 it may be so limited that browning will be practically unknown com- 

 mercially during certain seasons. 



CONCLUSION. 



During the four years in which the present investigators have 

 been studying this trouble, it has been found that seasons of very 

 high crop production have been practically free from internal 

 browning. During years when browning was prevalent the fruit 

 from trees producing very heavy crops has been relatively much 

 more nearly free from the trouble than neighboring trees that pro- 

 duced light crops. On a single tree it has been possible, by heavy 

 thinning and girdling of branches, to produce apples that tended to 

 brown badly, while partial defoliation of well-loaded branches re- 

 sulted in sound fruit. Heavy fertilization with manure tended to 

 increase the percentage of browning, and heavy nitrogen fertiliza- 

 tion increased browning markedly in all trees except those bearing 

 a very heavy crop of fruit. 



Apparently under the growing conditions of the Pajaro Valley 

 fruit tends to brown internally in storage when light crops of 

 large coarse-textured fruit are j)roduced. It is impossible for the 

 orchardist to control weather conditions, and it is not always pos- 

 sible to obtain a uniformlj^ heavy crop on the trees. Internal 

 browning apparently does not develop seriously, however, if storage 

 temperatures are held at 36° F. or above. It is particularly im- 

 portant that storage conditions be right during years of light crops 

 and large-sized fruit. 



SUMMARY. 



Certain varieties of apples when placed in cold storage for a long 

 season develop a brown discoloration in the flesh of the fruit which 

 has been designated " internal browning." This trouble is particu- 

 larly serious in the Yellow Newtown apples grown in the Pajaro 

 Valley district of California, where investigations have been car- 

 ried on for a number of years. 



This trouble is not caused by a parasitic organism but appears 

 to be brought about by certain conditions within the fruit itself. 



Apples from the Pajaro Valley have been found to be far more 

 susceptible to this trouble than those from an}' other section of 

 the country. This district has an extremely cool growing season, 

 coupled with high humidity and fertile soil conditions. 



Internal browning develops to a far greater extent in fruit held 

 at 32° than that kept at 36° or 40° F. Its occurrence to an extent 

 sufficient to be important commercially can be largely prevented by 

 storing the Pajaro Valley apples at 36° to 38° F. 



