EXPERIMENT STATION BULLETINS. -345 



per. The leaf hopper seemed to show a preference for certain varieties. 

 The Idaho Rural was one of the first to become seriously infested. This 

 variety was damaged earlj^ in the season and ripened prematurely. The 

 season of 1920 was more favorable for potato production, it being a more 

 nearly average season as to rainfall and invasion of insects. The experi- 

 mental evidence of two years would indicate that of the varieties tested, the 

 Early Ohio and Irish Cobblers have the lead in the early class and the Green 

 Mountain and Rurals in the late class where yield and quality are considered . 



SELECTION WORK WITH POTATOES. 



The potato selection work began in 1919 with tuber unit selection. About 

 three hundred tubers were selected from seven different varieties, which are 

 fairly well adapted to the Upper Peninsula. Those were planted four hills 

 to the tuber and the product of each tuber kept separate at harvest time. 

 A range in yield was obtained from .75 of a pound in the lowest producing 

 tuber to 9 pounds in the highest. The better tuber progenies from these 

 various varieties were planted in progeny rows in 1920. These progeny 

 rows were carefully studied as to their suitability for increasing. Mr. Weston 

 eliminated any that did not give promise of being characteristic of the va- 

 riety and Mr. Kotila eliminated any that gave an indication of possessing 

 undesirable disease characteristics. From those progeny rows, that proved 

 to be "breeding true to variety" and that appeared to be free from such dis- 

 eases as Mosaic, Curly Dwarf, Blackleg, etc., the best one or two progeny 

 from the standpoint of jdelding power were selected to be increased in 1921 

 on new ground isolated from other potato plants. These best progeny in- 

 creases will be subject to a very careful disease study in order that any dis- 

 ease infected plants may be rogued out and thus allow the harvesting in the 

 fall of high yielding disease free strains. The intention is to isolate a super- 

 ior yielding, disease-free stock of seed and have it increased under controlled 

 conditions. Such controlled conditions could probably best be reahzed on 

 an island similar to the Rosen Rj^e project on the South Manitou Island, 

 (article to be found in November 1920 issue of Experiment Station Quarterly). 



POTATO DISEASE INVESTIOATIONS. 



Potato disease investigations were first undertaken at the Upper Penin- 

 sula Station in the summer of 1919 in co-operation with and under the super- 

 vision of specialists at the Michigan Agricultural College in the Botany Sec- 

 tion of the Experiment Station. The aim of the work has been to study 

 those potato diseases which are most serious in the Upper Peninsula fields, 

 to determine their causes, and to recommend control measures. 



The three main lines of investigation which have been conducted are as 

 follows : 



1. Potato Seed Treatment. 



2. Investigation of Potato Blackleg. 



3. Investigation of Hopperburn. 



