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 
■Rath 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. So 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. Inability 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 difficulty 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 
affected with raspberry curl, than lighter soils which are ade- 
