Feb. 3, 1919 



Physoderma Disease of Corn 



151 



The results given in Table I show that the sporangia of P. zeae-maydis 

 may be carried by the wind in considerable numbers. With the abun- 

 dance of sporangial material which is present in the fields after the corn 

 plants have matured it is quite possible that many of the sporangia are 

 carried by even the very slight breezes. 



Further experiments were conducted at Clemson College, S. C, in 

 April, 1 91 8, to obtain additional information on the dissemination of 

 sporangia of the fungus by wind. Slides prepared as mentioned above 

 were placed on stakes without regard to direction in a field where the 

 com plants had been badly injured by P. zeae-maydis in 1917. The plants 

 were cut in the fall of 191 7 for shredding, but not until the sporangia had 

 been liberated in large numbers. At the time the slides were placed the 

 field was being planted to cabbage and most of the remaining parts of 

 the com plants had been plowed under. There was considerable wind 

 and rain during the time the slides were kept in the field. Table II 

 gives the results of these sporangium catches. 



Table II. — Results of sporangium catches of Physoderma zeae-maydis on slides placed in 

 fields at Clemson College, S. C, in April, igi8 



The results given in Table II show that a considerable number of 

 sporangia are carried by wind even after the plants have been removed 

 and the soil has been plowed. These sporangia were doubtless blown 

 from the soil surface as well as from the small parts of diseased plants 

 which remained uncovered. Some of them, however, might have 

 reached the lower slides through spattering rain drops. 



Overflowing streams or surface water flowing through infested com 

 fields after heavy rains may carry large numbers of sporangia to be 

 deposited along their courses. The disease has been found to be more 

 abundant on overflow lands and near streams. Within the infested area 

 the sporangia doubtless reach their host plants in some cases through 

 spattering rain water. 



Man is perhaps one of the most important agents by which the fungus 

 is disseminated. In removing diseased plants for stover, fodder, silage, 

 etc., large quantities of sporangia are carried to the barns, and some- 

 times they may be shipped considerable distances with this material, 

 After these products have been used as feed for animals, the barnyard 



