EFFECTS OF FREEZES ON CITRUS IN CALIFORNIA 247 



INTRODUCTION 



The recent injury to the citrus industry caused by the severe cold 

 weather of the first week in January, 1919, has again emphasized the 

 importance of having available for the use of growers data on the 

 effects of such freezes as a guide in handling injured fruit and trees. 

 Following the great freeze of January 5 to 7, 1913, a frost damage 

 survey was organized by the College of Agriculture under the direc- 

 tion of the Citrus Experiment Station and much valuable material was 

 collected. This information. has been summarized and is published 

 in this bulletin with the belief that it will be of service to growers in 

 handling the problems connected with this winter's freeze. 



Much of the data presented and the methods suggested are appli- 

 cable to any freeze, but some of the matter presented has historical 

 value only. The section on "Protection by Artificial Heating" will 

 be recognized as not being up to date. Even this section of the bulletin, 

 however, is believed to be of value, as it is a record of achievement 

 in the "big freezes" with what would now be considered very inferior 

 equipment. If growers succeeded so well with inferior equipment it 

 would seem certain that a grove, with modern equipment, could be 

 perfectly protected in another freeze of equal severity. To delay the 

 publication until such sections could be brought thoroughly up to 

 date would make its publication too late to be of any serivce in the 

 present freeze. 



This bulletin, then, is really a record of the freeze of 1913. While 

 there had been freezes in preceding years, in which citrus fruits and 

 various subtropical plants were somewhat injured, nothing so severe 

 and disastrous as this freeze had occurred in the state since the citrus 

 industry was started. 



Aside from the general field studies and observations, special studies 

 were made on the chemical and physical changes that took place in the 

 deterioration of frozen fruits. It is the purpose of this bulletin to 

 discuss such of the studies as it is thought will be of interest and value 

 to growers, in case of future freezes. No attempt will be made to 

 compare the relative degree of damage done to groves in various sec- 

 tions, as it is thought that the conditions shown in this freeze might 

 be reversed or much changed in another freeze, and such comparisons 

 might thus be misleading. 



Messrs. A. D. Shamel, L. B. Scott, and C. S. Pomeroy, of the U. S. 

 Department of Agriculture, cooperated with the Experiment Station 



