530 Forestry Quarterly 



Some results of the sulphuric acid treatment may be briefly 

 stated. In cases of beds treated before sowing, it was found that 

 if germination takes place at any time during the first month 

 after 0.25 ounce of acid per square foot is applied to the beds, it 

 will be necessary to give more than the usual nursery watering 

 during the germination period in order to insure freedom from 

 injury to seedlings. When the acid was applied at the time of 

 sowing, although in concentrations varying from 0.125 to 0.37 

 fluid ounce per square foot, there was no indication that the 

 pine seed itself was injured before the germination began, but in 

 case of the Jack pine, at least where the germination was prompt, 

 many seedlings were killed or injured after germination, unless 

 special protective measures were taken, even with the lowest of the 

 concentrations given above. In fact, after the seed begins to ger- 

 minate any application of sulphuric acid sufficient materially to 

 afYect the activity of the damping-ofT disease will cause the death 

 of the radicles of some of the pine seedlings. As a whole, the 

 disinfectants were most eflfective when applied at the time of 

 sowing. Even then precautions must be taken to prevent injury 

 to the roots. The best of these is to keep the surface layer of 

 the soil moist by frequent light waterings during the germinat- 

 ing period and until the root tips have penetrated at least ^ inch 

 into the soil. This procedure is based upon the fact that the 

 amount of water in the soil bore a direct relation to the amount 

 of injury, and that injury seldom occurred when the root tips 

 had penetrated to the depth mentioned above. Evaporation at 

 the surface of the soil increases the concentration of the poison 

 in the soil water until the injuring or killing point is reached. 



Jack pine was most liable and Western Yellow pine least 

 liable to injury by the acid treatment. This was not because the 

 Jack pine roots were more sensitive to the action of the poison, 

 but because the Yellow pine roots grew faster and sooner got 

 below the danger zone in the soil. The beds treated with acids 

 and so watered as entirely to prevent injury to the pines were 

 nevertheless so free from weeds that the cost of weeding the 

 treated beds during the whole season was only one-third that 

 of the untreated beds. 



C. D. H. 



