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XXXV. 



A DISEASE OF TOMATO AND OTHEE PLANTS CAUSED BY A 

 NEW SPECIES OE PHYTOPHTHOKA. 



By GEOEGE H. PETHYBEIDGE, B.Sc, Ph.D., 



Economic Botanist to the Department of Agriculture and Technical 



Instruction for Ireland; 



AND 



H. A. LAFFEETY, A.ECSc.I., 

 Assistant in the Seeds and Plant Disease Division of the Department. 



(Plates XLV.-XLVII.) 



[Head November 19, 1918 ; published February 4, 1919.] 



I.— Introduction. 



In the early summer of 1916 specimens of diseased young tomato plants 

 (Zycopersicum escidentum Mill.) were submitted from a nursery in the suburbs 

 of Dublin to the Seeds and Plant Disease Division of the Irish Department 

 of Agriculture for examination and report as to the cause of the malady and 

 the possibility of curing or preventing it. 



A preliminary examination of the specimens at once showed that the 

 trouble was not due to any of the commonly occurring diseases of the tomato. 

 On the contrary, the disease appeared to be one of a new type ; and a visit 

 was therefore paid to the nursery in question to examine further cases of it, 

 and to obtain information concerning its origin and degree of seriousness. 



It was learned that the disease was first noticed in this nursery three 

 years previously, only a few plauts being attacked at that time. In the 

 succeeding year it had become more serious, while at the time of our visit 

 nearly one-half of a large stock of young tomato plants were found to be 

 either dead or dying. In these three years, therefore, the disease had become 

 so well established in this particular nursery as to interfere very seriously 

 with the raising of young tomato plants. 



The same disease was discovered subsequently in two other nurseries, as 

 well as in some private gardens in the same locality, while, during the course 

 of our study of it, young tomato plants affected with it have been received from 



SCIENT. PROC. R.D.S., VOL. XV., NO. XXXV. 4 G 



JUN 15 



