DAMPING-OFF OF CONIFEROUS SEEDLINGS. 23 



in the first season's growth is not very important. If, however, it is 

 desired to transplant the stock at the end of the first season the 

 increase in size due to acid, at least in the jack pine, which is ordi- 

 narily most helped, may mean the difference between success and 

 failure. In a case of great increase in size, such as was secured by 

 the acid treatment of jack pine at the two nurseries in Kansas, the 

 economic results are more positive. It was entirely impossible to 

 raise 1 -year-old stock large enough to transplant without the use of 

 acid. With the acid treatment 1 -year-old seedlings were produced 

 which appeared to be in every way the equal of untreated 2-year-old 

 stock for transplanting purposes. The time and expense involved in 

 holding the stock for a second year in the seed beds were avoided. 

 At the Garden City nursery the advantage went even farther than that. 

 The seedlings in the untreated beds were so small that they could 

 not withstand winterkilling and were practically all killed before the 

 second growing season. The seedlings in the acid plats immediately 

 adjacent came through the winter practically without loss. While, 

 as already stated, the acid proved ineffective at this nursery so far as 

 the control of damping-off is concerned, on account of the carbonates 

 present in the soil, its effect on growth and the resultant freedom from 

 winter loss alone positively indicated its use on jack-pine beds in 

 combination with the toxic salts found most valuable for damping-off 

 control. 



WEED CONTROL BY DISINFECTANTS. 



At the nurseries where weeds are troublesome in the seed beds the 

 effect of the disinfectants on the weeds is probably the most important 

 of the secondary results of the treatment. The plants commonly 

 occurring as weeds seem on the whole much more sensitive to acids 

 and to copper and zinc salts than do the conifers. The result is that 

 treatments so worked out as to be entirely harmless to the coniferous 

 seedlings in the beds are found at a number of nurseries to keep the 

 beds almost entirely free from weeds during the first three or four 

 weeks after the germination of the conifers. This is just the time 

 when most weeds can be expected to appear in the untreated beds 

 and when the delicacy of the young conifers makes it difficult to do 

 even hand weeding without breaking or pulling up many of the seed- 

 lings. The economic value of this weed-control feature varies with 

 different nurseries. At some places the efficiency with which weeds 

 are controlled is less than at others. At some places weeds are not 

 numerous enough to make weed control a consideration of any very 

 great importance. The only place at which an attempt has been 

 made to reduce to a dollars-and-cents basis the value of the weed- 

 controlling effect of a damping-off control treatment is at Halsey, 

 Nebr. Approximate figures obtained from forest officers indicate that 

 the entire cost of the hand weeding required during the seasons consid- 



