EXPERIMENT STATION REPORTS. 259 



POTATO DISEASE WORK 



BY J. D. KOTILA 



Herewith report of work carried on by the Botany Section of the 

 Michigan Agricultnral p]xperiment Station at the TT. P. Experiment 

 Station during the iiscal year ending Jnne 30, 1928. 



As in preceding years, the work was contined primarily to investiga- 

 tion of potato diseases. Approximately 7 acres of land were devoted to 

 experimental work. 



Three acres of the south farm were devoted to an experiment to deter- 

 mine the relative elficiency of Bordeaux mixture and copper lime dusts 

 on Green Mountain potato vines. A four-row power sprayer was com- 

 pared to a four-row power dusting machine. The season was favorable 

 to leafhoppers, and hopperburn was abundant. This trouble and Early 

 Blight disease, which became epidemic early in September, were factors 

 which reduced the yield to the unsprayed i)lots very materially. The 

 Bordeaux plots whicli weie sprayed six times during the season remained 

 green much longer than the plots which had received a like number of 

 applications of copper-lime dust. The Bordeaux plots likewise out- 

 yielded the dusted plots. 



Unfavorable results having been obtained during the 1921 season on 

 the control of potato scab with applications of sulphur to the soil at the 

 rate of 300 pounds per acre, the 1922 experiments represented trials of 

 sulphur applied at higher rates,— 400, 600, SOO and 1200 and 1600 

 pounds per acre. Three acres of Rural New Yorker potatoes were de- 

 voted to these experiments. There was no noticeable effect on stand or 

 vine growth during the growing season. The data obtained at harvest 

 indicated that scab was not controlled by applications of inoculated 

 sulphur to the soil at the rates of 400, 600, or 800 pounds per acre. 

 The data from the plots which received 1200 and 1600 pounds of in- 

 oculated sulphur show a lower percentage of scab but this reduction was 

 counterbalanced by a higher percentage of sulphur injured potato tubers. 



An area of approximately half an acre was planted as a show plot 

 with potato seed stock affected with various diseases, — mosaic, leaf roll, 

 streak, rhizoctonia, etc., in order that anyone interested might be able 

 to study the symptoms of the more common potato diseases. 



Several isolated plots were planted with tubers of various varieties 

 which had been indexed in the greenhouse during the 1921-22 winter. 

 The vines remained healthy throughout the season and the progeny was 

 saved for increase during the 1923 season. 



I thank you for the interest you have shown and the hearty co-opera 

 tion you have given to facilitate the work of the Botany Section dur- 

 ing the past season. 



