REVIEWS 



The Control of Damping-Off of Coniferous Seedlings. By C. 

 Hartley and R. G. Pierce. Bulletin 453, U. S. Department of Agri- 

 culture. Contribution from the Bureau of Plant Industry. Washing- 

 ton. 1917. Pp. 32. 



This is an important piece of work, in so far as it seems to have 

 come near demonstrating the possibility of combating successfully the 

 damping-off disease, which is the bane of the conifer nursery. In 

 the first place, the cause of the disease, which for a long time was 

 wrapped in mystery, is chargeable to three parasitic fungi, Pythium 

 deharyanum Hesse, Fiisarium moniliforme Sheldon, and Corticinm 

 vaguni B. & C. var. solani Burt; and other species may also be 

 concerned. 



The economic importance of controlling the disease is increased 

 h\ the observation that often what losses are ascribed to poor germi- 

 nation per cent are really due to this disease. 



While there are some nursery practices which have a limited value 

 in reducing loss by the disease, such as the use of well-drained and 

 aerated soil, cover with gravel, coarse sand, moderate watering and 

 shading, the application of certain fertilizers, moderate density of 

 sowing, and time of sowing, all of which receive attention, disinfec- 

 tion of the soil seems the only effective way of .approaching the 

 problem. 



Experiments in seed-bed infection have been carried on for the 

 last seven years at a number of nurseries, repeatedly in seven localities, 

 and in fifteen locations in single seasons only. The materials experi- 

 mented with' were sulphuric acid, copper sulphate, zinc chloride, 

 formaldehyde, tankage, air-slacked lime, cane sugar, mercuric chloride, 

 charcoal. Altogether 115 tests were involved. These tests are cor- 

 related in a table and discussed in some detail. The work of other 

 investigators is also briefly referred to. Sulphuric acid seems to 

 have so far given the most satisfactory results, but must be carefully 

 handled. 



While costs of treatment vary considerably, the authors, from 

 indications, conclude, that even if only 20 per cent increase in plants 

 were secured, this minimum would pay for the treatment twice over. 



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