2 MANUAL OF TREE DISEASES 



Damping-Off 

 Caused by various species of fungi 



The damping-off diseases have commanded serious atten- 

 tion from all persons who have attempted to grow seedlings, 

 especially of conifers. Schreger, in an early compilation of the 

 facts known about tree diseases, published in 1795, writes about 

 the damping-off of beech seedlings. Since the growing of large 

 quantities of seedlings for forest planting was first attempted in 

 Europe, the earlier literature on damping-off appeared mostly in 

 foreign languages. American nurserymen have grown small 

 quantities for ornamental and shade tree stock for many years. 

 The increasing demands for large quantities for forest planting 

 were not supplied, however, by the production of the commer- 

 cial nurserymen. It is thought that the small quantity pro- 

 duced and high prices demanded for the stock were due mainly 

 to the difiiculties of handling the damping-off diseases. To-day 

 the growing of coniferous seedlings in federal and state nurseries 

 has developed until millions of trees are produced yearly. It 

 was during the development of these specialized nurseries that 

 the damping-o£F diseases in this country were studied, and 

 methods evolved for their control. 



Damping-off is a universal seedling trouble. The fungi 

 causing the disease are common soil-harbored organisms asso- 

 ciated with decaying plant material. Seedlings grown in new 

 soil may suffer from damping-off as severely as those in beds 

 which produced diseased plants the previous year. The seed- 

 lings of coniferous trees in general show marked susceptibility, 

 while those of deciduous trees are less often attacked. Beech 

 and maple seedlings, however, often suffer. When no pre- 

 cautions are taken, damping-off may kill practically the entire 

 stand of seedlings, especially when large numbers are grown 

 under crowded conditions. 



