FUNGOUS DISEASES OF PLANTS 



fungus may be perennial in brown or purplish-brown spots, and 

 from such areas the conidial stage of the fungus is produced the 

 following spring. The fungus, shown in Fig. 134, is known only by 

 the conidial stage, and the latter is developed throughout the season. 

 In artificial culture this Cladosporium grows readily, producing a 

 dense olive-black mycelium, with somewhat abnormal conidiophores 

 and conidia, but no other stage has been reported in such cultures. 



XII. CLADOSPORIUM: OTHER SPECIES 

 Cladosporium Cucumerinum Ell. and Arth. This fungus, like 

 many other species of the genus, is occasionally parasitic. It occurs 



upon melons, producing 

 sunken spots on the fruit, 

 and sometimes on the 

 stems. This trouble is ap- 

 parent, as a rule, only dur- 

 ing very moist weather, 

 and under such circum- 

 stances the conidial stage 

 of the fungus is developed 

 abundantly over the af- 

 fected areas, which ap- 

 pear olivaceous in color 

 (Fig. 135). 



Cladosporium fulvum 

 Cke. Leaf mold of tomato. 

 This fungus is common 

 during moist weather, pro- 

 ducing on tomatoes a leaf 

 blight which shows itself 

 in its effects upon the up- 

 per surface by a moderate 

 yellow discoloration, which may eventually appear as true spots. 

 On the under surface the olivaceous growth of the fungus may 

 be seen. As the disease progresses the entire leaf may become 

 yellowed, and often whole plants may be defoliated. The fungus 

 is an active parasite, although belonging to a genus most of the 

 members of which are saprophytic in habit. 



FIG. 135. CLADOSPORIUM CUCUMERINUM ON 

 MELON 



