DAMPING-OFF OF CONIFEROUS SEEDLINGS. 25 



the cheap and simple copper-sulphate treatment proved entirely sat- 

 isfactory, with the alternative of zinc chlorid in case the copper salt 

 should ultimately prove in any way unsatisfactory. At four of the 

 seven, all that appears necessary to be done is to apply the disin- 

 fectant, and thereafter let the beds take care of themselves. Al- 

 though specially frequent watering is required during the germinating 

 season by treated beds at the other three nurseries, the cost of this, 

 as has been shown for Halsey, is not excessive, and the amount of 

 extra watering required to protect the germinating seedlings at the 

 remaining two nurseries is less than at Halsey. 



At the localities considered in the last part of the table, where the 

 tests have been mainly or entirely limited to a single season, some 

 facts of interest have been developed, though at none of them have 

 the best control methods been definitely determined. At Dundee 

 and Cass Lake a sufficient number of independent series of tests were 

 made to show without doubt that some one of the treatments which 

 resulted well will be found satisfactory for regular use. At most of 

 the other nurseries in this second division the tests have been 

 preliminary in character and are only indicative. At 13 of the 

 14 localities listed in the second part of the table, the results of 

 the tests indicated the value of one or more of the treatments 

 tested. At 9 of these 13 the indications were that the disease 

 could be controlled by a treatment which would not make neces- 

 sary any special watering of the beds. At the one nursery where no 

 results were obtained (Pocatello) sulphuric acid was the only substance 

 tested under proper watering conditions, and its failure is easily ex- 

 plained by the presence of soil carbonates. 



Considering separately the soil treatments employed, it appears 

 that there are four reasonably promising disinfectants for use on 

 coniferous seed beds. The writers have experimented with approxi- 

 mately 50 different substances, alone or in combination, in the 

 treatment of seed beds, and these tests, in conjunction with the re- 

 sults of the writers and of others which are summarized in Table III, 

 indicate that the most generally satisfactory substances for such use 

 are sulphuric acid, copper sulphate, zinc chlorid, and formaldehyde, 

 of which the acid is the most promising. 



The use of sulphuric acid has been reported at 20 different 

 localities. At 17 of these it has given indications of value. Its 

 failure at Pocatello and Garden City is merely an indication that 

 it will not succeed in the presence of large quantities of soil car- 

 bonates. At Glen view, 111., the tests were very preliminary and 

 therefore not sufficient to show that it was valueless. It has become 

 established as a regular part of nursery practice at all nurseries where 

 it has been repeatedly tested, with the exception noted of the one 

 where the soil contained carbonates. At several nurseries in the 



