BUSH FRUIT PRODUCTION 



Mosaic is the most common form. It ap- 

 pears as a yellowish mottling of the leaves, 

 with darker green blisters between the veins. 

 Plants infected with leaf curl, on the other 

 hand, have dark green leaves which are tightly 

 curled, the edges rolling inward toward the 

 under surfaces. 



Both mosaic and leaf curl belong to that 

 mysterious group of mosaic diseases which is 

 arousing the concern of plant pathologists 

 everywhere. The organisms which cause them 

 seem to be incredibly minute — at least they 

 never have been seen. They are spread from 

 plant to plant by certain aphids or plant lice. 



The only practical control measure which 

 has been suggested is the removal of infected 

 plants as they appear. The roots, too, should 

 be removed in so far as possible and new 

 shoots from remaining roots should be de- 

 stroyed until the last root is dead. The 

 disease dies with the plant and when the old 

 plant is gone, a new; one may safely be set 

 in its place. 



Crown Gall is another incurable disease 

 which sometimes appears. This disease oc- 

 curs on many plants and appears as wartlike 

 growths on the roots. Infected plants are 

 weakened and rendered more susceptible to 

 drouth and winter injury. Crown gall spreads 

 46 



