DAMPING-OFF OF CONIFEROUS SEEDLINGS. 9 



At nearly all of the other nurseries sulphuric acid was also found 

 successful in controlling damping-off. However, because of dif- 

 ferences in soil and climate, the treatments required elsewhere dif- 

 fered in some details from that at Halsey. On a still lighter sand 

 in Kansas sand hills, which was probably also somewhat more alka- 

 line, it was found that damping-off could be controlled best by a 

 heavier treatment of acid — one-fourth fluid ounce per square foot in 

 ordinary spring-sown beds, and five-sixteenths or three-eighths ounce 

 in beds sown in the fall or very early spring. The watering required 

 during the germinating period to prevent injury to the pines was 

 less than at Halsey. The losses in untreated beds at this nursery were 

 exceptionally heavy. In the treated beds it was not possible to 

 reduce the damping-off loss to as low a figure as at Halsey, probably 

 because of the common occurrence of Fusarium moniliforme, a fungus 

 exceptionally able to quickly reinfect treated beds. The success of 

 the treatment from the economic standpoint, however, was greater 

 than at Halsey. Without the treatment, failure occurred in the 

 seed beds more often than success, and stock could not be raised at 

 a reasonable expense. With the treatment, success was the rule, 

 and the economical production of stock became possible. The dif- 

 ference in stand between treated and untreated plats at this nursery 

 is shown in Plate I, figure 2. 



At a single nursery on a fine sandy soil near Morrisville, Pa., it was 

 found that it was more difficult than at Halsey to prevent acid injury 

 to germinating seedlings.. This was a nursery at which tests were 

 made during a single season only. It is mentioned at this point merely 

 to show the difference in behavior of acid in different soils. Even one- 

 twelfth fluid ounce per square foot caused injury to the pines at Mor- 

 risville. Indications from the small series of tests conducted there 

 were that one-eighth ounce of acid per square foot would probably 

 prove effective against damping-off and harmless to coniferous seed- 

 lings if followed by sufficiently frequent watering during the germi- 

 nating period. It is likely that this soil was slightly acid to start 

 with. 



In marked contrast to the experience at Morrisville are the results 

 obtained at Fort Bayard, N. Mex., Monument, Colo., and Haugan, 

 Mont. At all of these places acid at the rate of three-sixteenths ounce 

 or more per square foot has been applied to the beds at sowing in 

 repeated tests, without any injury to the seedlings that could be 

 detected by the forest officers in charge at the nurseries. At Fort 

 Bayard Mr. H. C. Turner has tested the acid very thoroughly for four 

 successive seasons and in quantities up to five-eighths ounce per square 

 foot without finding any injury to seedlings. Even three-sixteenths 

 ounce proved reasonably efficient in decreasing damping-off, and the 

 five-eighths ounce treatment reduced the loss to less than 1 per cent. 

 60142°— Bull. 453—17 2 



