April, 1914.] Report on Raspberry Curl or Yellows. 287 



From general appearances, the root system of diseased plants 

 seems normal. This disease is peculiar in that we may have 

 diseased and healthy plants of the same or different varieties grow- 

 ing side by side. This has often been observed by the writer where 

 Cuthbert and Early King were growing in the same row, the former 

 variety always being the more susceptible. It is also of interest 

 to note that raspberry curl may make its appearance in a plot 

 even though cane blight has never been known to occur among 

 such plants. The writer has likewise noticed that although cane 

 blight may be very severe in a patch of berries, a careful search did 

 not reveal the presence of a single case of raspberry curl. 



Cause of Raspberry Curl. As yet no definite cause can be 

 assigned to this disease. Stewart and Eustace (1902), intimated 

 that it might be related to the so-called physiological diseases, 

 such as, peach yellows, while others are attacking this problem 

 with the expectation of locating a pathogen. Paddock (1904-5), 

 noticed that the disease was more pronounced where plants were 

 growing in a soil which had a high water table. This in part agrees 

 with the observations made by the writer, particularly where 

 plants were growing in a heavy soil. It was thought at one time 

 that insects might be contributing factors toward the production 

 of these curled leaves. The opinions of entomologists which the 

 writer has at hand, however, do not substantiate this. 



The writer has made numerous attempts at isolating a causal 

 organism, selecting different parts of diseased tissue of various 

 ages, but up to the present time no organism has been obtained 

 which has been conclusively shown to be the cause of this disease. 

 Old crowns frequently contain various fungi, but their connection 

 with the appearance and production of raspberry curl, in the writ- 

 er's opinion, is problematical. An attempt was made to corre- 

 late this disease with the occurence of crown gall on raspberry 

 plants, but of the hundreds of plants examined, no relationship 

 was found to exist. 



At present the writer is making a histological study of diseased 

 tissues. vSo far, he has been unable to locate bacteria or fungi in 

 typical specimens which have been examined. This, however, is 

 not to be interpreted as meaning that a pathogen does not exist 

 in the diseased tissues of the raspberry plant. Inabihty to dis- 

 cover an organism up to this time may be due to various factors, 

 such as the size of the organism concerned or the difhculty in 

 properly staining and differentiating the very fine mycelia within 

 the host tissue. Further studies are being made along this line, 

 and a more detailed report will be published later. 



The writer has had occasion to observe that heavy, compact 

 soils, lacking proper drainage, are more liable to have plants 

 afifected with raspberry curl, than lighter soils which are ade- 



