NURSERY PRACTICE ON TTTE NATIONAL FORESTS. 71 



However, it has the advantage of never making necessary special 

 watering after the seed are sown. 



At the Monument Nursery hot dry soil sprinkled over and worked 

 into the soil of an affected area has proved quite effective in checking 

 damping-off. 



Sowing at certain seasons as a preventive of damping-off is indi- 

 cated by the experience of some nurseries. Western yellow pine and 

 Douglas fir at the Boulder, western yellow pine at the Savenac, 

 and Douglas fir at the Wind River suffer the most severe losses, 

 and jack pine at the Bessey Nursery suffers least, when the sowing 

 is done in the fall. 



WINTER MOLDING. 



A type of injury which has proved serious only at the Cottonwood 

 Nursery is due to molding. Molding is caused by heavy accumula- 

 tions of snowfall remaining on the nursery area longer in the spring 

 than normal. When the snow goes off the plants are found pressed 

 down flat upon the ground, with foliage brown or black and moldy. 

 In some cases the stems remain green and the plants recover, but 

 usually the plants succumb entirely. Norway, Engelmann, and blue 

 spruce have never suffered very heavily, particularly after the stock 

 has passed its first year. Douglas fir is the worst affected species and 

 suffers most in 1-0 and 2-0 stock. Western yellow pine has never 

 been much affected as seedling stock, but losses have occurred in the 

 1-2 transplant beds. No effective preventive is known for this at 

 present. Douglas fir suffers less severely in drill-sown than in 

 broadcast-sown seed beds. 



WIND INJURY. 



Wind may whip, break, and dry up plants, or in loose soils drift 

 the soil over them. Windbreaks of some bushy shrub or tree or of 

 artificial construction are the most efficient remedy. 



SUMMER DROUGHT INJURY. 



Summer drought injury x is a physiological trouble rather than one 

 due to fungi. It is caused by an insufficient amount of water or shade ; 

 is evidenced by the dying of the roots, a yellowing or browning of 

 the tops, and the final death of the plants and is most usual during 

 the hot, dry months of summer. It has often been called simply blight 

 and, until recent investigations by Mr. Hartley, was thought to be due 

 to fungi. Summer drought injury has caused considerable damage 

 at the Bessey Nursery and is more likely to be a source of danger at 

 a nursery where the soil is loose and subject to very rapid drying 



1 For full discussion, see Bulletin of the United States Department of Agriculture No. 44, 

 "The Blight of Coniferous Nursery Stock," by Carl Hartley, of the Bureau of Plant 

 Industry. 



