12 BULLETIN 453, U. S. DEPARTMENT OF AGRICULTURE. 



appear probable. At Cass Lake, Minn., acid was tested on seed beds 

 of Norway pine (Pinus resinosa) during a period of weather so abnor- 

 mally cold and wet that the seed lay in the ground for a number of 

 weeks before germination was completed. Under these conditions, 

 for the first time in the writers' experience, the acid treatment of the 

 beds at the time of sowing resulted in decreased germination. No 

 special watering was needed to prevent injury to the tips after the 

 seedlings began to come up; in fact, very frequent watering given one 

 bed resulted in less germination and therefore poorer results than in 

 acid beds with no extra watering. Despite the decrease in germina- 

 tion, the acid beds, because of the almost complete control of damping- 

 off by the treatment, finished the season with an average of 135 seed- 

 lings for every 100 in the untreated plats, and the acid plats which 

 were not given excessive water had 151 seedlings for every 100 

 in the untreated plats. This fact and the fact that acid beds which 

 had first been treated with lime and were thereby kept from injury to 

 the seed produced 228 seedlings for every 100 in the untreated plats 

 indicate that in ordinary seasons the treatment with acid alone will 

 be entirely successful. The use of lime with acid is usually undesirable 

 because by neutralizing the acid it permits the parasites to resume 

 work soon after treatment. Formaldehyde gave better results than 

 acid at Cass Lake. While it is thought that this would not be the 

 case in a normal season, it is evident that further tests are needed to 

 determine what treatment to use. 



The danger in drawing conclusions from the results of three or 

 four test plats is shown especially well by the results obtained by 

 Prof. H. H. York, of Brown University, in testing treatments recom- 

 mended by the writers. Treatments involving five-sixteenths ounce 

 of sulphuric acid, five-eighth ounce of zinc chlorid, and 2\ ounces 

 of cane sugar, respectively, per square foot of bed, resulted in final 

 stands from 4| to 15 times as dense as in most of the untreated plats. 

 One untreated plat, however, gave a stand as dense as that on the 

 treated plats. This throws doubt on the reliability of the results on 

 the other plats and indicates that only repeated tests, each with 

 plenty of untreated plats for abundant comparison, are reliable 

 enough to be used as a basis for conclusions. 



At several of the nurseries mentioned above other soil treatments 

 were tried with success. At Glenview, 111., where acid failed, copper- 

 sulphate treatment resulted in doubling the final stand. The good 

 results obtained on otherwise untreated soil at Dundee, 111., by the 

 addition of cane sugar were rather surprising; indications of damp- 

 ing-off control by sugar were also observed at Garden City, Kans., 

 East Tawas, Mich., and Providence, R. I. Further tests are required. 

 At East Tawas, a test of acid in an unfavorable season did not give 

 as good results as desired, while formaldehyde resulted in a doubled 

 stand. 



