58 James Stewart Wiant 



sulfate, the two chlorides of mercury, and several preparations containing 

 organic mercury compounds. As far as the writer knows, this is the first 

 report of controlling the damping-off of conifers by this type of application. 

 The results suggest considerable promise for the method, in point of both 

 convenience and cost of treatments. 



In using the dry chemicals at nurseries where the broadcast method of 

 sowing is practiced, it will be necessary to disinfect the thin layer of sand 

 which is used for covering the seed. This can be done by mixing the chemi- 

 cal with the sand prior to covering, or by adding a very small amount of 

 the chemical to the surface of the beds after the seed has been covered. 



Another problem arises with the use of dry chemicals, in that, with the 

 exception of the organic-mercury preparations, none of the materials used 

 in these tests can now be obtained on the market in the most desirable 

 form. In the case of aluminum sulfate there is available a pulverized 

 form from which can be sifted out a product sufficiently finely divided to 

 be applicable for this type of treatment. It would be highly desirable, 

 however, to have available a much more finely divided preparation of 

 aluminum sulfate. The problem is being taken up with the manufacturers 

 of this material. 



There is also the problem of devising a suitable apparatus for applying 

 the dry chemicals. The rather crude methods used in the present tests 

 were effective, but they could be improved upon by employing some type 

 of sifter or other device for obtaining a more rapid and uniform distribution 

 of the fungicide. 



With regard to the relative merits of the different chemicals, the results 

 of these investigations indicate that liquid treatments with aluminum 

 sulfate, 9 mercuric chloride, Semesan, Uspulun, or sulfuric acid, and with 

 dry treatments of aluminum sulfate, Bayer 1 1-6, or either of the two chlo- 

 rides of mercury, were practically equally effective in controlling damping- 

 off. Thus, in certain experiments significant differences could not be 

 demonstrated between the results with these materials. In other experi- 

 ments such differences existed, but the relative position of a given chemical 

 was not constant throughout several experiments. Bayer dust, which 

 was used only in light applications, gave less favorable results than did 

 the above-named materials. However, since Bayer dust contains the same 

 mercury compound (except in smaller amounts) as does Bayer II— 6, it is 

 believed that heavier applications would probably be as effective as the 

 latter preparation. Dipdust was not uniformly so effective as the other 

 materials. No explanation is offered, since the content of organic mercury 

 was higher than that of other preparations which gave more favorable 

 results. Semesan Bel, which was used to a limited extent, was effective 

 in the larger applications. Semesan Jr. gave excellent results in several 



» Suggested rates of application with aluminum sulfate were furnished to the writer by Dr. Carl Hartley, 

 of the Office of Forest Pathology, United States Department of Agriculture. 



