RASPBERRY DISEASES : 405 



similar factors. Authorities agree that fungi cannot be the 

 cause. Likewise entomologists say that insects are not con- 

 cerned. The red spider has been suspicioned, but conclusive 

 evidence is lacking. If bacteria are the cause, they have not 

 been seen. It is possible that they are present, but are so very 

 small that they are easily overlooked. It has been noticed 

 that the disease is more pronounced where plants were growing 

 in soil which had a high water table. Plants growing on soil 

 having compactness and lacking drainage are more liable to 

 exhibit yellows than lighter well-drained soils. It has been 

 suspicioned as having some connection with crown-gall and 

 cane-blight, but careful observations do not substantiate this 

 view. 



Control. 



No preventive measures are known, and little hope is in sight 

 until the causal nature is understood. Fungicides have proved 

 themselves worthless in controlling the disease. A few rec- 

 ommendations have been suggested, and the more important 

 of these may be noted : (1) in planting red raspberries obtain 

 plants from localities where raspberry-yellows is known not 

 to occur; (2) select varieties which have shown resistance in 

 the neighborhood ; (3) select for a plantation-site a light, or 

 medium-heavy, adequately drained soil ; (4) irrigation is help- 

 ful where practiced ; (5) destroy diseased plants. 



REFERENCES 



Stewart, F. C., and Eustace, H. J. Raspberry cane blight and rasp- 

 berry yellows. II. Raspberry yellows. New York (Geneva) 

 Agr. Exp. Sta. Bui. 226 : 362-364. 1902. 



Melchers, L. E. A preliminary report on raspberry curl or yellows. 

 Ohio Naturalist, 14 : 281-288. 1914. 



Green, S. B. Leaf curl of raspberry. Minnesota Agr. Exp. Sta. Ann. 

 rept. 1894 : 230. 1895. 



