230 Diseases of Greenhouse Crops 



white spots, the centers of which are occupied by a 

 scanty or profuse black fungus growth, which is 

 made up of the spores of the fungus (fig. 47, d 

 and e.). The spots are dry, rather shrunken, circu- 

 lar or somewhat elongated. If the node of the stem 

 is attacked, the disease spreads sufficiently to involve 

 the adjoining foliage as well. The stem itself be- 

 comes somewhat girdled and in time is also killed. 

 Usually, however, the spots are confined to the 

 foliage. 



The Organism. The mycelium is dark brown, 

 (fig. 48, a.). The conidiophores arise from a stroma, 

 usually from one to twenty-five in number, and each 

 one to four septate (fig. 48, b, e and f.). The coni- 

 dia are borne in chains (fig. 48, d.), and in structure 

 are very typical of other Altemarias (fig. 48, d.). 

 The fungus grows well on various culture media. On 

 media poor in sugars, the mycelium and spores are 

 lighter in color and smaller in size and diameter. 



Control. All infected material should be collected 

 and destroyed by fire. Spraying with a standard 

 fungicide is also recommended. From the observa- 

 tions of Stevens and Hall,* the variety Mrs. Thomas 

 W. Lawson appears to be the most susceptible to this 

 disease. As far as possible, this variety should be 

 avoided. 



Anthracnose 



Caused by Volutella sp. 



Symptoms. The disease usually attacks the base 



* Stevens, F. L., and Hall, J. G., Bot. Gaz. 47:409-413, 1909. 



