quate experimental data. Therefore, some of the 

 harmful effects might have been due to other causes. 

 Arthur and Stuart ( 5 ) give a most comprehensive 

 review of the early work on this subject. The long 

 list of publications indicates the interest in this sub- 

 ject at the turn of the last century. Corn smut was 

 suspected of causing general weakness, falling out of 

 hair, abortion, convulsions, paralysis, and even death 

 of animals (5). The so-called corn-stalk disease of 

 cattle also was attributed to corn smut (5). Recently. 

 Ivanoff i 165 1 attributed bronchopneumonia of cattle 

 in Bulgaria to corn smut. 



Much of the data on injurious effect of feeding 

 corn smut is still contradictory. The preponderance 

 of evidence indicates that fairly large quantities of 

 corn smut can be fed to cattle, horses, and other 

 animals without any apparent ill effect (5). In 1921, 

 Ficke and Melchers ( 94 ) fed large quantities of corn 

 smut to cows and horses without harmful results. 

 Some cows relish the smut and milk production was 

 not impaired. 



Smut Control. — Many attempts have been made 

 to control corn smut by eradication, such as seed 

 treatment and destruction of smut galls: protection by 

 spraying with chemicals and application of biological 

 agents: cultural practices involving crop rotation and 

 application of fertilizers: and '"immunization." the 

 development of resistant varieties. 



Seed treatment. — All attempts to control corn smut 

 by seed treatment have failed (5). Therefore, this 

 subject is chiefly of historical interest. Although Tillet 

 (335) and others (5. 25. 34) proved that smutty 

 seed did not produce smutty plants, seed treatment to 

 control smut was recommended until about 1900 (5). 

 To what extent it was actually practiced is not known. 



Most of the experiments on seed treatment, at lea^t 

 in the U.S.A.. were initiated before Brefeld's classic 

 work on life history of corn smut was generally 

 known. 



Bonafous (25). agriculturist during the early part 

 of the nineteenth century, suggested treatment of 

 corn with quicklime, marine salt, potash, and other 

 compounds for control of corn smut. Kiihn (see 5). 

 as late as 1879. recommended soaking corn seed in a 

 0.5% solution of copper sulfate and this soon became 

 a standard recommendation for control of corn smut. 



In the U.S.A.. Henry (133). in 1883. reported that 

 seed treatment with copper sulfate and with carbolic 

 acid gave no smut control. Arthur and Stuart like- 

 wise failed to reduce smut by treating the seed with 

 a solution of copper sulfate and ammoniacal cupric 

 carbonate. Arthur and Stuart (5) and Stewart i327> 

 made extensive studies on treatment of seed with hot 

 water in an attempt to control smut. All tests on seed 

 treatments were negative. [For additional references 

 on seed treatment, see Arthur and Stuart (5).] 



U. maydis is readily carried on corn seed; con- 

 sequently, infested seed lots could easily be one method 

 of long-distance dissemination of the pathogen. There- 

 fore, it would be advisable to treat seed with a good 

 fungicide before it is introduced in smut-free areas 

 or countries such as Australia. 



Sanitation. — For almost 200 years, removal and 

 destruction of corn smut galls were recommended by 

 manv to reduce corn smut (5. 25 i. During the earlv 



part of the nineteenth century, the European writers 

 stated that cutting away the young gall would help 

 to prevent the weakening of the plants: somewhat 

 later, the purpose also was to reduce the inoculum. 

 This practice of smut removal was also strongly 

 recommended in the U.S.A.. especially late in the 

 nineteenth century and the early part of the twentieth 

 century. In fact, it is still commonly recommended 

 especially for sweet corn in small gradens. There is 

 no adequate experimental proof, however, that such a 

 practice is of any value, especially in a region where 

 the pathogen is common. 



The cutting and ensiling of green corn also have 

 been suggested as a partial control method, primarily 

 because Piemeisel 1 260. 261) proved that the smut 

 spores were destroyed in the process of ensilage. 



Crop rotation. — Crop rotation has also long been 

 recommended as a means of reducing the amount of 

 corn smut, but there is inadequate evidence to support 

 this practice. In 1896. Hitchcock and Norton (143) 

 found that treatment of soil with chemicals did not 

 reduce the prevalence of smut. Selby and Hickman 

 ( 298 ) observed more smut on corn growing on newly 

 broken sod than on a field planted to corn for many 

 years. Wilcoxson and Covey (357). on the basis of 

 3-year field tests, actually obtained a lower percentage 

 of tassel smut when corn followed corn than when 

 it followed a cereal crop. The cause of these dif- 

 ferences in amount of smut is not known. 



A survey of the literature clearly indicates that the 

 severity of smut cannot be attributed to a particular 

 agricultural practice. Wind is an effective carrying 

 agent for both chlamydospores and sporidia and this 

 fact must not be overlooked when studying crop 

 sequences. 



The successful eradication of U. maydis from 

 Australia must be attributed to destruction of smut 

 galls and infected plants, plus the prohibition of 

 growing corn in the infested area. This is an excellent 

 example of successful eradication of a destructive 

 pathogen after it became established in a new country 

 (207 i. 



Application of fertilizers. — Burger (38), as early as 

 1809. stated that too much manure favors the develop- 

 ment of corn smut. Ever since the early work of 

 Brefeld with manure, it has generally been assumed 

 that the application of manure to the land increased 

 the prevalence of smut. Botanists (5, 36. 190) con- 

 sidered manure a suitable medium for multiplication 

 of sporidia. It was known to increase vigor of the 

 host and hence was thought to predispose corn to 

 smut infection. Most of their conclusions are based on 

 field observations and on meager experimental data. 



Starr's (324) work indicated that the commercial 

 fertilizers that increased vigor also tended to increase 

 the amount of smut. Phosphate used alone reduced it. 



Schaffnit and Yolk (288) found that in greenhouse 

 tests nitrogen increased susceptibility, whereas a defi- 

 ciency in nitrogen increased resistance to smut. Both 

 an excess and a deficiency in potassium increased 

 susceptibility. Yolk (346) found that an excess of 

 XPK favored the development of smut. Greenhouse 

 results based on artificial inoculation are not necessarily 

 good criteria of field resistance to corn smut. 



Walter (350). on the basis of a 4-year field test. 



32 



