29:^ 



DISEASES OF ECONOMIC PLANTS 



gradually extend in all directions, involving the whole 

 root. Older spots, 2-5 cm. across, often break or crack 

 irregulurlj' near the center. This 

 deca}^ differs from the soft rot in 

 that the spots are dry and hard 

 and that it is present upon the 

 roots before digging. With the 

 hand lens very small, hairlike, 

 black structures, 1 mm. high, are 

 seen studding the centers of the 

 diseased areas. These are the 

 beaks of the pycnicha of the causal 

 fungus. 



Upon young sprouts before they 

 are set out tiie disease causes black, 

 dead [)atchcs, esperially at the base 

 of the shoot or even upon the young 

 leaves. The wood of the stem may 

 be bi-owiied. Such sprouts if set 

 result in enfeebled plants with dis- 

 eased roots. 



Tile fungus throws myriads of 

 spores into the .soil. This disease 

 tims falls under the general class 

 of soil di.seases. 



In addition to the suggestions 

 given on page (i)i, es|)ecial precau- 

 tion should i)e exercised to avoid 

 sets already- alVeclcd. IJadly af- 

 fected siioots are easy of rc'cognilion, but the closest 

 scrutiny is needed to (aiil out those oiil\' sligiitly affected. 



Fic. r27. — liliicU rot. of .sweet 

 [Xitat >. Orijiiiial. 



