346 



STATE BOARD OF AGRICULTURE. 



Fig. No. 18. 1919 Seed treatment and disease plats. These plats are planted In half-peck lots which 

 allows for repetition and takes care of differences in results due to soil variation. 



Seed Treatment.* 



The seed treatment experiments carried on during the 1919 and 1920 

 seasons have been duphcates of those conducted at the College during the 

 same seasons, the seed stock and treatments being identical at both places. 

 In 1919 the treatments were made at East Lansing and half of the seed sent 

 to Chatham for planting. In 1920 the procedure was reversed and all treat- 

 ments were made at the Upper Peninsula Station and half of the seed sent 

 to the College for planting. Corrosive sublimate, mercuric cyanide, and 

 formaldehyde were used as disinfectants and various lengths of treatment 

 were tried. 



RHIZOCTONIA. 



Although the experiments at'Chatham and East Lansing were identical, 

 the data obtained at the former place during the two seasons have not been 

 comparable in all respects to those obtained at the latter. In all cases much 

 b.tter control of Rhizoctonia (Black Scurf) and Scab was obtained at the 

 College than at the Upper Peninsula Station. Excellent control for Rhi- 

 zoctonia and Scab was obtained at East Lansing by corrosive sublimate 

 treatment for 30 minutes. Thirty-minute treatment with formaldehyde 

 also controlled Scab but was not effective for Rhizoctonia. While good con- 

 trol for Rhizoctonia was obtained at the Upper Peninsula Station by use of 

 corrosive subhmate with both the 30-minute and hour-and-a-half treatments, 

 the control was not as complete as at the College. The longer treatment 

 (one and one-half hours) gave better results at Chatham in 1920 than the 

 shorter (30 minutes) treatment, whereas in 1919 the 30-minute treatment 

 was just as effective. At the College during both years the short treatment 

 was foimd to be as effective as the long time treatment. 



The corrosive sublimate treatment of potatoes to control Rhizoctonia 

 and Blackleg is recommended as follows: 



Select only sound, desirable tubers for treatment. Scabby, bruised, or 

 partially rotted tubers are unsafe. 



*For description of the potato diseases discussed below see Special Bulletin No. 85, "Michigan 

 Potato Diseases." 



