UNITED STATES DEPARTMENT OF AGRICULTURE 
Xfl3&S , In cooperation with the 
Pennsylvania Agricultural Experiment Station and the Pennsylvania 
Department of Agriculture 
DEPARTMENT BULLETIN No. 1156 
Washington, D. C. ▼ May, 1923 
INVESTIGATIONS OF POTATO WART. 1 
By Freeman Weiss, Pathologist, Office of Cotton, Truck, and Forage Crop Disease 
Investigations, Bureau of Plant Industry; C. R. Orton, Pathologist, Pennsylvania 
Agricultural Experiment Station; and R. E. Hartman, Pathologist for Potatoes, 
Pennsylvania Department of Agriculture. 
CONTENTS. 
I.— The varietal and species hosts of Synehvtriuin endobiotiemn. By Freeman Weiss and C. It. 
Orton 1 
II. — The adantability and use of wart-immune varieties of the potato in the quarantined areas of 
Pennsylvania. By R. E. Hartman 17 
III.— The stability of wart immunity. By Freeman Weiss 20 
I.— THE VARIETAL AND SPECIES HOSTS OF SYNCHYTRIUM 
ENDOBIOTICUM. 
By Freeman Weiss and C. R. Orton. 
TESTS WITH POTATO VARIETIES AND SEEDLINGS. 
When the disease of the Irish potato known as wart was discovered 
in the United States in 1918 2 the question of the reaction of American 
potato varieties to the newly introduced parasite assumed a posi- 
tion of first importance. The fact that certain potato varieties 
remained entirely free from infection even when grown in soils 
thoroughly infested by the pathogen, as shown by the behavior of 
other varieties, had been known in Europe for a number of years, 
and the cultivation of such resistant varieties was even then regarded 
as the only means of avoiding the severe crop losses occasioned by 
this disease. Variety tests conducted in England had included 
several American sorts, and these were reported upon in 1919 3 
but aside from this, no information was available as to the reaction 
of American varieties to this disease. However, the severity of 
infection on the heterogeneous stocks commonly grown in the wart- 
1 This report is based upon cooperative investigations carried on by the Bureau of Plant Industrv ami 
the Federal Hnrticullural Board of the United Stales Department of Agriculture, the Fennsylvani:i*Apri- 
cultural Experiment Station, and the Pennsylvania Department of Agriculture. 
1 Sanders, James G. The discovery of European potato wart disease in Pennsylvania. In Jour. Eoon . 
Ent., v. 12, p. 8&-90, pi. 3. 1919. 
3 Snell, John. Or.nskirk potato trials. Annual report, 1918. In Jour. Bd. Agr. [Gt. Brit.], Sun. 18, 
p. 68-102, fig. 20-33 on 8 pi. 1919. 
33570— 23— Bull. 1156 1 
