103 



PUi^^GI AIS^D FUISTGICIDES 



leaves of raspberry and blackberry; the germinating 

 tubes enter the stomata, or breathing pores^ of the leaf, 

 develop a mycelium inside, and finally produce on the 

 surface the spores of the teleuto stage, which has here- 

 tofore been considered an entirely different fungus, 

 called by botanists Puccinia jjechicma. These Puccinia 

 spores are believed to be washed ofi to the underground 



FIG. 48. SECTION OF BLACKBERRY LEAF, SHOWING DEVELOPMENT OP 

 ORANGE RUST SPORES. MAGNIFIED. 



shoots, and to infect them with the mycelium, which 

 subsequently produces the orange spores of spring. 



Blackberries are most commonly affected by this 

 fungus — especially certain varieties — but blackcap rasp- 

 berries often suffer also. 



Treatment. — All diseased canes should be cut out 

 and burned as soon as they show signs of disease, leaving 

 none to develop spores to infect other plants. In con- 

 sidering varieties, select — other things being equal — those 

 least liable to the disease. Insist on your neighbors 

 keeping the rust in check, and also look out for wild 

 plants that have it. A spraying with fungicides will 



