152 - Journal of Agricultural Research voi. xvi. no. 5 



manure is utilized as a fertilizer, and no doubt carries with it a large 

 number of viable sporangia which serve as a source of infection to corn 

 plants grown on the land in the future. There is considerable doubt as 

 to the possibility of the sporangia's remaining viable after passing 

 through the silo or the body of the animal, as no experiments have been 

 conducted to determine this point. However, sufficient sporangial 

 material to serve as a means of dissemination escapes the action of the 

 silo and the digestive processes of the stomach of the animal. This 

 would be especially true with stover and fodder, where the tough, thick 

 parts are not eaten by the animals. Hay, unhusked com, or any other 

 plant products removed from infested fields and shipped to various 

 parts of the country would serve as an ideal means of disseminating 

 P. zeae-maydis. This would hold true especially in late fall, when the 

 sporangia are being liberated in so great an abundance. 



There is a remote possibility of the dissemination of the fungus to 

 a certain extent by being carried on the seed. However, very little of 

 the disease has been seen, even on the outer husks of the ears. When 

 the ears are husked, the only chance for sporangia to be present on the 

 seed is for them to be brought in by some foreign agent, as they are not 

 produced inside the husks. If the husking is done in the field it is quite 

 probable that some of the loose sporangia will lodge on the husked ears. 

 If, however, a few of them are present on the surface of the kernels of com 

 when planted the chances are that they will not be able to infect the re- 

 sulting crop because they are buried with the seed in the drill row, where 

 no cultivation is given and there is practically no chance for them to be 

 disturbed. t 



If they were to germinate in the soil, the zoospores would have no 

 chance to reach the surface to infect the com plants. There is a possi- 

 bility, however, that the sporangia might live over in the soil until the 

 following year, or even longer, and finally come in contact with com 

 plants, though the possibilities of dissemination in this manner seem to be 

 comparatively small. 



POSSIBLE CONTROL MEASURES 



No definite means of control has yet been discovered for the* disease. 

 However, certain measures may be recommended for reducing the amount 

 of sporangial material present which would have a tendency to reduce 

 the severity of the attacks by the fungus. These measures may be out- 

 lined as follows : 



(A) The quantity of sporangia present could be greatly reduced by 

 burning the old infected plants after the com has been harvested, but this 

 would be a destructive practice, especially in the South, where the disease 

 is important and where organic matter is so badly needed in the soil. If 

 the plants could be cut into very fine pieces and plowed under deep 

 enough so that they would not be disturbed by ordinary cultivation the 



