186 Proceedings of Indiana Academy of Science 



dated and it is likely that this is identical with the potato anthracnose 

 recently reported from Ohio (9). 



Inasmuch as black leg (fig. 8C), caused by Bacillus phytophthorus, 

 is one of the cool-climate diseases, it was not surprising to find it 

 occurring to some extent in the early market garden crop near Indian- 

 apolis. On May 20 the disease was causing characteristic symptoms on 

 about one per cent of the plants in certain of these fields which, it ap- 

 peared, had been planted with home-grown seed. In these same fields 

 there was a considerable loss due to the destructive effect of Rhizoctonia 

 solani on the young shoots (fig. 8, A and B). The occurrence of 

 numerous blanks in the rows was attributable to this disease and a 

 prevalent stunting of the plants was found to be due to the killing of 

 the main shoot by a Rhizoctonia lesion below the ground line and the 

 subsequent development of a latei-al shoot from a point below the 

 canker. Typical, brown, Rhizoctonia lesions were frequently present on 

 these secondary shoots and also on the roots. This destructive activity 

 of Rhizoctonia early in the spi'ing under Indiana conditions is exactly 

 what should be expected in the light of Richard's (35) determination of 

 the low soil temperature optimum (18° C) for the parasitic activities 

 of this organism upon the young shoots. The extremely destructive 

 effect of the disease, especially on the young shoots, emphasizes the 

 necessity of disinfection of the seed for the early crop. The black 

 scurf stage of this disease on tubers was generally prevalent throughout 

 the state. 



Scab, caused by Actinomyces scabies, is state-wide in its occurrence. 

 In a field near Lafayette much deep scab, such as Coons has attributed 

 to the secondary action of mites in the scab lesions, was noted. In 

 another field there was a very high incidence of the early stage of the 

 so-called russet scab. These lesions were small shallow rounded spots 

 of blackened tissue which later may crack and check and produce the 

 roughened russet scab appearance. 



Owing to the excessive rains, the tubers of the late crop very fre- 

 quently showed extreme cases of enlarged lenticels. This condition was 

 common in low ground in one field observed near Lafayette. A pre- 

 liminary test indicates that the water loss during four months storage 

 from tubers with enlarged lenticels is 17 per cent more rapid than in 

 the case of normal tubers. 



A grower in Franklin County found about 50 per cent of his crop 

 of Early Six Weeks potatoes affected with internal brown spot. In 

 a highly productive muck field in Fulton County planted to a late crop 

 of Rurals, overgrown tubers and second gi'owth knobs were of very 

 frequent occurrence. Sunburn or greening occurred to a considerable 

 extent this season because the soil was frequently washed away from 

 the upper tubers thus exposing them to the sun. In the muck field 

 mentioned above there was also a rather high percentage of tuber rot, 

 some due to Fusarium, some apparently to bacteria. The Fusarium 

 rot was of a peculiar type, since it was usually associated with the death 

 of rather extensive cortical areas. The bacterial rot was more or less 

 confined to the central tissues of the overgrown tubers. 



Rotting of the seed pieces in the soil was the most important .source 



