Feb. i, 1921 Onion Smudge 717 



this experiment was sufficient to show that sprays could not be used 

 successfully for the control of smudge. 



Dusting of the sets in the crates at harvest time with lime or sulphur 

 has been suggested by Thaxter (33). In 1916 and 1918 dusting ex- 

 periments with lime, sulphur dust, and dry Bordeaux powder were con- 

 ducted without any positive results. This is to be expected, since, as 

 a rule, the outer scales of the bulbs became infected before harvest 

 and a disinfectant applied externally could hardly prevent further 

 invasion of underlying scales. 



The importance of thorough curing and prevention of exposure to 

 humid conditions after harvest has been emphasized by Thaxter (33), 

 Clinton (10, p. 333) , Massee (17) , and Stevens and True (30) . The experi- 

 ments reported on the effect of drying of bulbs at harvest have shown 

 that rapid dehydration of the outer scales at this time checks further 

 invasion by the fungus to a large degree. Observations in the field by 

 the writer during the years 1914 to 1920 indicate that even the best 

 natural curing weather to be expected in the Middle West is not sufficient 

 to do more than partially check the disease on seriously infected fields. 



Artificial curing offers a possible measure of control for smudge, and, 

 as already pointed out (37) , preliminary experiments indicate that neckrot 

 can also be checked by this treatment. Extensive control experiments 

 carried on in the Chicago district in 191 8 have shown that thorough dry- 

 ing very soon after harvest is necessary in order to check smudge materi- 

 ally. In the set-growing district a large portion of the crop is grown on 

 contract to be delivered at a central warehouse as soon as it has cured 

 sufficiently. The expense involved in this treatment would almost 

 necessitate that they be dried at a central point, preferably at the place 

 of storage. Therefore, in order to handle the large quantity received, a 

 fairly rapid process of drying would be essential. 



Further experimental work is necessary before artificial drying can be 

 recommended as a general practice, and the results of control experi- 

 ments are reserved for later publication. In the meantime, the most 

 applicable remedial measures consist in prompt harvest and the best 

 use of natural climatic conditions in curing the white onion set crop, 

 including all possible protection from moist weather. This should be 

 followed by storage in a well-ventilated warehouse held as nearly as pos- 

 sible at 33 to 36 F. 



SUMMARY 



(1) Smudge is one of the most common diseases of white onion Gets in 

 Wisconsin and Illinois. 



(2) It occurs also on shallot (Allium ascalonicum) and leek (A. porrum). 



(3) The disease was first described by Berkeley in England in 1851 and 

 is now widely distributed in Europe and America. 



