7i6 



Journal of Agricultural Research 



Vol. XX, No 9- 



SPREAD OF SMUDGE IN STORAGE 



It has been claimed that smudge spreads from infected to healthy 

 bulbs in storage (17, 29). It is to be expected that under unusually 

 moist conditions this might occur. However, since considerable mois- 

 ture is necessary for sporulation and infection, the conditions which 

 prevail in good storage houses are not conducive to rapid spread of 

 the disease. Several experiments have been conducted during the course 

 of this investigation in which healthy bulbs have been marked and mixed 

 in lots of badly diseased sets. A summary of these experiments appears 

 in Table IX. 



Table IX. — Spread of smudge in storage 



Experi- 

 ment 

 No. 



Storage conditions. 



Standard onion warehouse. . . . 



do 



Cool cellar 



....do 



Moist chamber at room tem- 

 perature. 



Length 

 of ex- 

 peri- 

 ment. 



Days. 



154 



103 



66 



208 



36 



.Num- 

 ber of 



healthy 

 bulbs 

 used. 



34 



40 

 20 

 30 

 20 



Condition at end of experiment. 



All healthy. 



2 bulbs showed slight infection. 



All healthy. 



Do. 

 6 showed slight infection. 



It was found that there was little or no spread of the disease under 

 ordinary storage conditions or in a cool cellar. In a saturated atmos- 

 phere some infection of healthy bulbs occurred. In practice, then, some 

 spread from diseased to healthy bulbs is to be expected where sets are 

 exposed to rain or very humid atmosphere such as might occur during 

 the curing period. However, with fairly dry sets kept in cool, well- 

 ventilated storage new infections are probably negligible. 



CONTROL OF THE DISEASE 



The control of this disease is obviously connected closely with the 

 handling of the crop at or immediately following harvest. 



In 1 91 5 a spraying experiment was conducted on a plot of white sets 

 at Racine, Wis. The development of the disease in this plot has been 

 described on pages 708-709. Various schedules were used with 4-4-50 

 and 8-8-50 Bordeaux mixture plus soap, 4-50 copper sulphate, and 1-10, 

 1-16, and 1-32 lime sulphur. The sprays were applied upon the bulbs 

 and necks of the plants. Contact with the soil probably reduced the 

 disinfecting property of the chemicals, and their adhesiveness was limited 

 by the nature of the scales and leaves of the onion. No beneficial results 

 were secured even where the first application was made before the first 

 signs of the disease appeared and where the spraying was continued at 

 intervals of three to eight days until harvest. The complete failure of 



