formaldehyde or a combination of the two and obtained a considerable degree of 

 control. In regard to his method of appHcation we quote from his summary (36:51). 



"To apply formalin, use at rate of one pound commercial formahn in 25-30 gallons 

 of water (1 oz. to 1 Ji-2 gals.) and apply with drip attachment on seed drill at rate 

 of 500-700 gallons of solution per acre for onion set. seeding (about K-K as much 

 for field onions) or apply with sprinkler upon the scattered seeds until well mois- 

 tened, then cover with earth promptly. 



"Apply ground quick lime or stone hme, better the former, at the rate of /5 to 125 

 bushels per acre just before seeding, on the freshly prepared soil. If applied by 

 drill, harrowing will not be required; if broadcast, harrowing should precede 



Stone (39) recommended formaldehyde at the rate of 1 lb. to 30 gals. (1-240) or 

 1 oz. to a gal. of water (1-128). With the improved tank which he describes in 

 detail he found that about 1200 ft. of drill could be treated with one gallon of the 



solution. . 1111 



Within recent years all other methods except the apphcation ot formaldehyde 

 have been abandoned, since this has given good results and is the most convenient. 

 Various concentrations of the solution and quantities per acre or given length of 

 row have been recommended. The most recent and thorough investigations have 

 been those in Wisconsin by Walker (47). After experiments of several years' dura- 

 tion he recommended the use of formaldehyde* at a dilution of 1-128 apphed at the 

 rate of 200 gallons per acre, or one gallon to about 185 feet of drill (1-128-2960, or 

 approximately equal to our 1-128-3000 formula). 



In England, "\^^iitehead (52:444) recently made control experiments in which he 

 treated the seed with various percentages of sulfuric acid and with paraform, other 

 experiments in which the soil was treated with soot and salt, paraform, bleaching 

 powder, lime, nitrate of soda, sulfur and hme, calcium cyanamide, carbon bisulfide 

 and formaldehjTle. In the summary of the work he recommends only formaldehyde. 

 We may briefly summarize the methods of control which have been recommended 

 in the past and their present status: 



1. Modification of the fertilization of the land has been of no avail. W e do not 

 believe, however, that the possibilities of this field of investigation have been ex- 

 hausted. 



2. Removal or destruction of diseased onions or refuse is wasted time. 



3. Rotation of crops is of little, if any, value because of the length of time during 

 which the fungus lives in the soil and because of the facihty with which it may be 

 introduced from neighboring fields. It is also not economically practicable on high- 

 priced onion land. 



4. Search for resistant varieties has yielded nothing up to the present, but 

 should be continued. 



5. Burying the surface soil is too expensive to merit consideration. 



6. Sterihzation of the entire field by heat or chemicals is also too expensive. 



7. The use of larger quantities of seed is ineffective. 



8. The use of transplanted seedlings is an absolute preventive, but suchfa 

 method of culture is considered too laborious by growers of the Connecticut Valley 

 region. , . . , 



9. The use of sets is just as sure a preventive. This is being practiced more ex- 

 tensively every year, not only because of the smut situation but also because of less 

 damage from thrips and of larger yields. The early harvesting of the crop , however, 

 has distinct disadvantages from the storing and marketing standpoint. _ 



10. Chemicals other than formaldehyde have proved worthless, injurious, or at 

 best, very much inferior to that chemical. Sulfur and lime have given the most 

 promise, but are no longer used. . 



11. The use of formaldehyde is the only treatment which is now recommended 

 or extensively used. The principal objections to the formaldehyde method are— 



(1) the use of large quantities of water which greatly increases the labor 

 at planting time, and 



(2) danger of injury to the seed. 



*Walker also tried (48:323~) the sulphur and lime method described by Sirrine and Stewart but found it 

 inferior to the formaldehyde method "both as to efficiency in controlling the disease and ease of proper 

 application." 



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