130 Diseases of Greenhouse Crops 



is possible, however, to produce celery in the green- 

 house which is of a quality far superior to that grown 

 out of doors. The self-bleaching varieties such as 

 the Kalamazoo seem to be well adapted for forcing. 

 The White Plume seems to have a tendency to go 

 to seed, and the Golden Self-blanching is subject to 

 heart rot. Celery requires an abundance of mois- 

 ture. A lack of it will cause such a setback to the 

 plants that they may never recover. Too high or 

 too low a temperature has the same detrimental 

 effect. 



Diseases of the Celery 



Celery is subject to numerous diseases. Success 

 with the crop demands great care in the production 

 of healthy plants. 



Soft Rot, see Cauliflower, p. 126. 



Late Blight 



Caused by Septoria petroselini Desm. var. apii Br. 

 and Cav. 



Symptoms. The disease first attacks the lower 

 leaves of the stalk, producing irregular spots with- 

 out a definite boundary line. When the spots be- 

 come numerous the foliage withers and dries up 

 (fig. 18, a.). The disease attacks the leaves as well 

 as the stalks, rendering the affected plants useless 

 for the market. In storage, plants affected with late 

 blight will keep very poorly or rot altogether. 



The Organism. The fungus mycelium is hyaline, 



