252 JOURNAL OF FORESTRY 



Besides, secondary advantages are secured, in that germination is stim- 

 ulated, the size of seedHngs is increased, and weed control is assisted. 

 While these experiments are not conclusive, the authors attempt 

 to suggest detailed treatments under different conditions, at least 

 experimentally, and give the following summary of their own experi- 

 ments : 



1. By damping-off — the most serious difficulty encountered in 

 raising coniferous seedlings — is meant the killing of very young seed- 

 lings by parasitic fungi. 



2. To decrease losses from the disease excessive moisture and 

 shade should be avoided, without inviting drought or white-spot 

 injury to the base of the stem. Damping-off can often be decreased 

 by putting beds on very sandy soil. Seed should not be sown any 

 thicker than necessary. It appears better to sow broadcast than in 

 drills. Late fall sowing results in decreased losses at some nurseries 

 and is worth trial. Ptoper attention to all of these measures will 

 decrease the losses from damping-off, but at most nurseries they are 

 not sufficient really to control the disease. 



3. The addition of lime, wood ashes, and, in some cases, nitrogenous 

 fertilizers, seems to increase damping-off. Soil alkalinity appears to 

 favor the disease. No effect has been noted from green manures. 

 The use of unrotted stable manure has had very bad results; properly 

 rotted manures seem less objectionable. Tankage, charcoal, and cane 

 sugar are the only nondisinfectant substances w'hich have to date 

 given any hope of disease control. 



4. Soil disinfection has so far proved the best method of com- 

 bating damping-off. Of many methods tested, treatments with sul- 

 phuric acid, copper sulphate, zinc chloride, and formaldehyde have 

 proved the most satisfactory. The disinfectants, however, behave 

 (juite differently at different nurseries. The acid has on the whole 

 given the best results. Heat disinfection has been only partly effective. 

 Disinfection by acid or copper sulphate is cheaper than by the other 

 methods commonly recommended. 



5. In addition ,to decreasing damping-off after the seedlings come 

 up, the chemical disinfectants above mentioned, when properly used, 

 cause an increase in the apparent germination and are very helpful 

 in controlling weeds. This latter effect alone at some nurseries pays 

 the entire expense of the treatment. Application of sulphuric acid 

 has, furthermore, at some places resulted in marked increases in the 

 late season growth of pines. 



