THE RHIZOCTONIA DAMPING-OFF OF CONIFERS, 



AND ITS CONTROL BY CHEMICAL TREATMENT 



OF THE SOIL 1 



James Stewart Wiant 



In 192-4 the writer began a study of the fungicidal properties of certain 

 organic mercury compounds in comparison with various inorganic chemi- 

 cals. Early experiments in greenhouses demonstrated that several of 

 these materials were effective in controlling damping-off of coniferous 

 seedlings. Field tests were then carried out in a small experimental 

 nursery at Ithaca, New York, during the season of 1925. The results 

 obtained suggested the advisability of continuing the investigations on a 

 more extensive scale. An attempt was therefore made to determine the 

 importance of damping-off in a number of the larger nurseries in the 

 northeastern United States and the neighboring provinces of Canada. 

 It was found that damping-off was a serious problem in seven of the eleven 

 nurseries from which replies were received. In none of these seven nurser- 

 ies, and in but one of the other four, were treatments with chemicals being 

 systematically employed for controlling the disease. The need for further 

 work in eastern nurseries was therefore apparent, and arrangements were 

 made to establish a field laboratory at the nursery of the Keene Forestry 

 Association, Keene, New Hampshire, where investigations were carried 

 on during the seasons of 1926 and 1927. 



Since Rhizoctonia was almost the only pathogene involved in these 

 experiments, the larger part of the work was done on the particular 

 damping-off disease caused by this fungus. 



HISTORY 



This review aims to note the more important work on the damping-off 

 of conifers, and to call special attention to those papers having a direct 

 relation to the present investigations. A more detailed review of the 

 literature prior to 1921 may be found in the excellent paper of Hartley 

 (1921). 



The problem of damping-off early engaged the attention of German 

 foresters and nurserymen, who first attempted the mass production of 

 coniferous seedlings. Much of their work was observational in character. 



1 Also presented to the Faculty of the Graduate School of Cornell University, June, 1928, as a major 

 thesis in partial fulfillment of the requirements for the degree of doctor of philosophy. 



Author's acknowledgments. The writer wishes to express his appreciation to Dr. H. E. Thomas 

 and Dr. D. S. Welch, under whose direction these studies were made, and to other members of the staff 

 of the Department of Plant Pathology, New York State College of Agriculture, who have offered sugges- 

 tions during the course of the work; to the Bayer Company, which established the fellowship under which 

 the investigations were conducted; and to A. K. Proell and other officers of the Keene Forestry Association 

 for their cooperation in making available the facilities of their nursery. 



