Abstracts. 305 



INVESTIGATIONS ON THE MOSAIC DISEASE OF 

 THE IRISH POTATO.* 



This is a preliminary paper describing the results of re- 

 search conducted upon potato mosaic in four laboratories dur- 

 ing the years 1916-1919. After discussing the geographical dis- 

 tribution, the previous work concerning the effects upon yield, 

 and the characteristic symptoms, evidence is presented upon 

 various phases, summarized as follows. 



Potato mosaic decreases the yield decidedly. It is trans- 

 mitted by the tubers of affected plants and is thus maintained 

 in a stock from year to year. It also spreads in the field so that 

 healthy plants may have progeny partly or wholly diseased. 

 While the disease is characterized by certain physiological ab- 

 normalities, its cause is an infectious substance that can be 

 transferred from plant to plant by means of grafting, plant 

 juice, and plant lice. Transmission by plant lice was demon- 

 strated in a number of experiments of various kinds. Two 

 species common upon potato plants were used. Transmission 

 in the field has been greatly reduced, but not entirely elimi- 

 nated, by the removal of diseased plants from seed plots, while 

 hill selection has been much less successful as a method of 

 control. 



It appears that in order to reduce the detrimental effects 

 of the disease it is necessary both to avoid diseased stock and 

 to prevent field infection of healthy stock by plant lice. 



*This is an abstract of a paper by Donald Folsom and certain co- 

 operating members of the Bureau of Plant Industry, having the same 

 title and published in the Jour. Agr. Research, Vol. XVII, No. 6, pp. 

 247-274. 



