DAMPING-OFF OF CONIFEROUS SEEDLINGS. 19 



COST OF DISINFECTANT TREATMENTS. 



" 



Because of the differences between the nurseries where tests have 

 been made, both in the details of the treatment used and in the scale 

 of the operations and the equipment of the nursery in such matters 

 as water supply, it is impossible to make any statement as to the 

 exact costs of treatment. 



At two of the nurseries (Fort Bayard, N. Mex., and Haugan, 

 Mont.) mentioned in the foregoing pages, at which the treatments 

 have been in use long enough to permit a definite statement, all that 

 is needed is an application of acid solution to the beds just after 

 sowing. The treated beds thereafter require no more attention than 

 do those untreated. At six other nurseries, where the acid has 

 been in use for a less time, the same appears to be true, while for a 

 seventh nursery, where copper sulphate gives the best results, the 

 same simple method of application appears satisfactory. For these 

 nine nurseries, then, the treatment which has so far appeared most 

 effective involves no expense except that of the single disinfectant 

 application. Different amounts of disinfectant are required for 

 different soils, and because of the rather high cost of transporting 

 sulphuric acid the price of that disinfectant varies greatly in different 

 localities, so that exact costs of the treatment can not be given. It 

 is very evident, however, that both the sulphuric-acid and the 

 copper-sulphate treatments applied in this way are decidedly cheaper 

 than either the formaldehyde or heat disinfection methods as used 

 in out-of-door seed beds' of tobacco and other truck crops. At 

 many railroad centers sulphuric acid can be obtained in carboy lots 

 for 2 \ cents per pound 1 or even less, while copper sulphate should not 

 ordinarily exceed 8 cents per pound. 1 With copper sulphate one- 

 fourth avoirdupois ounce and sulphuric acid one-fourth fluid ounce 

 per square foot will be sufficient or more than sufficient at most 

 nurseries. Judging from the experience of truck-crop experimenters 

 and from the results of the writers and others with formaldehyde at 

 several nurseries, one-fourth to one-half fluid ounce per square foot 

 of the more expensive formaldehyde will be needed on most soils to 

 secure sufficient disinfection. If it develops that it is necessary to 

 use the tight cover prescribed by most writers to prevent premature 

 evaporation and to treat additional soil for use in covering the seed 

 after sowing, these items will further increase the expense of for- 

 maldehyde treatment. The expense of steam disinfection of out-of- 

 door seed beds of tobacco is given by Johnson 2 as $7.50 to $10 per 

 thousand square feet of bed. This is a much higher cost than is to 

 be anticipated with acid or copper-sulphate treatment. 



1 These prices prevailed prior to the outbreak of the European war. It is assumed that the present 

 higher prices are temporary. 



2 Johnson, James. The control of diseases and insects of tobacco. Wis. Agr. Exp. Sta. Bui. 237, p. 10, 

 1914. 



