Raspberry Yellows or Mosaic 261 



made. The disease is even found on legumes, sometimes being mis- 

 taken for the nodules of nitrogen-gathering bacteria. A character- 

 istic gall as found on raspberry roots is shown at Fig. 38. A knot 

 on a blackberry cane may be seen in Plate VIII. 



The galls sometimes afford lodgment for other parasites, such as 

 fire-blight, root-rot, and the like. Overfed plants seem most subject 

 to attack. The more vigorous a plant the larger the tumor, as a rule. 

 Hairy-root of the apple is due to the same or to a very closely related 

 bacterium. 



A very peculiar and interesting fact in connection with this dis- 

 ease is that in its habit of growth and development and in the forma- 

 tion of connecting "stroma" it is very similar to the development 

 of cancer in man. Apparently it may very properly be called a 

 plant cancer, as suggested by those who have given it most careful 

 study in recent years. 



Treatment. No cure is known for the trouble. The bacteria are 

 out of reach, where no external treatment can affect them. Affected 

 stock of all kinds should be scrupulously avoided; neither should 

 healthy stock be planted on infected land. The disease is very 

 prevalent among red raspberries and blackberries, the so-called 

 cane-knot of the latter being apparently only one form of it. For 

 this reason it may be unwise to plant these fruits among valuable 

 young orchard trees. Rigorous nursery inspection in many of our 

 states is now doing much to reduce the spread of this disease. 

 Reference. 



Bur. of Plant Indust. Bulls. 213 and 255. 



RASPBERRY YELLOWS OR MOSAIC 



Raspberry yellows is a troublesome disease which is not well under- 

 stood, its cause being as yet unknown. It is of such frequent oc- 

 currence on Marlboro plantations that it is frequently spoken of 

 as the Marlboro disease. Plants attacked by it have a stunted, 

 yellowish appearance, somewhat suggestive of the Bermuda lily 

 disease. The fruiting branches are small, often not over half their 

 usual length. The leaves are small, curled downward at the edges, 

 and faintly mottled with yellow. Some of the berries dry up with- 

 out ripening; others ripen but are small and flavorless. Many of 



