SEEDLING DISEASES AND INJURIES 5 



present in all soils, their presence may not become evident if 

 conditions are adverse to their development. All damping-off 

 pathogenes are markedly influenced by temperature, soil 

 moisture and the humidity of the atmosphere. A relatively 

 high temperature, moist and compact soil and a humid at- 

 mosphere furnish ideal conditions for these fungi, while lower 

 temperatures and drier conditions of soil and atmosphere may 

 check successfully a destructive development of these organisms 

 after some damage has already been accomplished. 



Control. 



Since damping-off may be caused by any one of numerous 

 species of fungi and may occur under such variable conditions, 

 no general rules for treatment can be prescribed which will 

 apply in all cases. The control of damping-off may be effected 

 by one of two general methods : (1) protection of the seedlings 

 by maintaining conditions of temperature and moisture which 

 interfere with the destructive development of the pathogenes; 

 (2) eradication of the pathogenes from the soil of the seed-bed 

 by means of disinfectants. 



(1) Protection. 



Every investigator agrees that much can be accomplished 

 in the control of damping-off by giving careful attention to 

 the manipulation of soil moisture, temperature and atmospheric 

 humidity. At the same time, it is realized that one may 

 find it difficult, in regulating the amount of moisture and 

 other factors, to preserve the equilibrium necessary to grow 

 seedlings, and at the same time to prevent the growth of the 

 fungi. The following method of procedure is advised : 



Each seed-bed should be provided with upright frame, with 

 wire-mesh sides and removable top, which can be made into 

 half-shade or full-shade by laying on laths. 



The seed should be sown on the surface of the prepared 

 soil and covered to the desired depth with clean dry sand 



