Feb. i, 1921 Onion Smudge 713 



RELATION OF STORAGE CONDITIONS TO THE DISEASE 



The study of the disease in storage has been directed toward the 

 solution of three problems: (1) The importance of smudge as a cause 

 of premature sprouting of sets; (2) the extent of shrinkage, if any, 

 which can be brought about during the storage of onion sets; and (3) 

 the amount of new infection or actual spread from diseased to healthy 

 bulbs occurring during the holding period. While the data on these 

 points are by no means complete and the factors involved in the progress 

 of the disease during the storage period by no means fully studied, the 

 experiments here reported upon throw some light on the matter. 



Observations on the first two questions were made in a standard onion 

 set warehouse at Morton Grove, 111. In practice, onion sets are stored 

 in crates about 4 inches deep with slatted bottoms, piled so as to allow 

 a 1- to 2-inch space between each two crates to facilitate circulation of 

 air. Sets are placed in storage during September and October. The 

 temperature is gradually lowered, following seasonal changes, until it 

 approaches o° C. (32 F.), an attempt then being made to hold it slightly 

 above this point. During extremely cold weather some artificial heat 

 in the house is necessary to prevent freezing, while ventilation is con- 

 stantly needed to remove excessive moisture. 



The experiments were carried on during the winter of 191 8-1 9. The 

 extremely mild weather during this season prevented the temperature 

 of the house from being held as close to o° C. as is commonly the case, 

 while, on the other hand, ample opportunity for ventilation was afforded. 

 Continuous records of temperature and relative humidity were secured 

 by means of a Friez hygro-thermograph. The temperature gradually 

 lowered during October and November, the minimum temperature reach- 

 ing 0.5 C. (33 F.), on November 23, while the maximum temperature 

 commonly reached 12.7 C. (55 F.) during this period. During Decem- 

 ber, January, and February the temperature fluctuated between 0.5 

 and 7. 2 C. (33 and 45 ° F.). The relative humidity varied between 65 

 per cent and 85 per cent during October and November, while through- 

 out the remainder of the period it seldom went above 75 per cent and 

 not often below 60 per cent. 



RELATION OP SMUDGE TO SPROUTING 



Two lots of onions were used in these experiments, and, since they 

 differed somewhat as to time of maturity and method of handling, they 

 are here considered separately. 



Experiment i. — Bulbs averaging about 1 inch in diameter were 

 selected from a lot of white sets harvested early in August and brought 

 into storage on August 22, 1918. Two groups were secured, one con- 

 sisting of 49 bulbs badly spotted with smudge and the other containing 

 47 perfectly healthy sets. The two lots had thus been grown and han- 

 dled alike and presumably differed only as to infection with smudge. 



