352 Diseases of Greenhouse Crops 



cury rises above 65 degrees, ventilation should be re- 

 sorted to in order to lower the temperature. High 

 temperatures force the plants to foliage with a de- 

 terioration in blossoms. Violets thrive in a soil 

 that is moist but well drained. The soil should be 

 watered enough to keep it moist at all times, but it 

 should never remain saturated for any length of 

 time. Violets should be given all the ventilation 

 possible every time the weather permits it. 



Diseases of the Violet 



Violets under glass are subject to numerous dis- 

 eases. Success with this crop requires that these 

 troubles be kept in check to a minimum. 



Cladochytrium Root Rot 



Caused by Cladochytrium viola Berl. 



This trouble is found in Europe, where it was 

 first described by Berlese.* It has not yet been re- 

 ported in the United States. This disease is mani- 

 fested as swellings on the roots. The parasite is 

 intercellular with branched mycelial threads. The 

 globose zoosporangium terminates with an open tube 

 through which the zoospores escape. Resting or sex- 

 ual spores have not been recorded for this species. It 

 is not likely that it will become an active parasite 

 of forced violets. 



•Berlese, A, N., Riv. Patol. Veg. 7:167-178, 1901. 



