NURSERY PRACTICE ON THE ' NATIONAL FORESTS. 69 



Susceptibility of species to damping-off in Forest Service nurseries. 



Nursery. 



Savenac. 



Boulder 2 . 



Trapper Creek . 

 Monument 



Bessey. 



Fort Bayard . 



Cottonwood.. 

 Beaver Creek . 

 Pocatello . 



Pilgrim Creek.. 



Converse Flats. 

 Wind River 



Page Creek 



Species. 



Most susceptible. 



fPinus ponderosa • 



i Pinus strobus ' 



I Pinus monticola i 



FPinus sylvestris 

 Pseudotsuga taxifolia . 

 Pinus ponderosa 



Pinus monticola 



/ Pinus austriaca 



\Pinus ponderosa 



/Pinus resinosa 



\ Pinus divaricata 



/Pinus attenuata. 

 1 Pinus sylvestris. 



/Picea engelmanni 



t Pseudotsuga taxifolia ' 



Pseudotsuga taxifolia . . . 



I Pseudotsuga taxifolia ' . . 

 Sequoia washingtoniana ' 

 Pinus jeffreyi. 1 

 Pinus sylvestris. J 



/Pinus ponderosa x 



\Pinus jeffreyi 1 



/Pseudotsuga taxifolia > . . 

 \Larix occidentals < 



Pinus lambertiana. 



Least susceptible. 



Pseudotsuga taxifolia. 

 Larix occidental's. 

 Picea engelmanni. 



[ Pinus austriaca. 



Pinus ponderosa. 3 

 Pseudotsuga taxifolia. 

 Picea engelmanni. 

 Pinus austriaca. 

 Pinus sylvestris. 

 Pinus ponderosa. 

 Pinus ponderosa. 

 Pinus jeffreyi. 

 Juniperus monosperma. 4 

 Juniperus pachyphloea. 4 

 Cupressus arizonica. 4 

 Pinus edulis. 4 

 Pinus monticola. 4 

 Pinus ponderosa. 4 

 Pinus contorta. 4 

 fPinus po derosa. 4 

 \ Pinus contorta. 

 (Pinus sylv V1 

 i Pinus austi 

 I Pinus pondei^a. 1 



! Pinus ponderosa. 4 

 Libocedrus decurrens. 4 



Libocedrus decurrens. 1 

 Cedrus deodara. 1 

 f Pinus monticola. 1 

 J. Pinus ponderosa. 1 

 (Abies nobilis. 1 

 [Pseudotsuga taxifolia. 1 

 < Pinus ponderosa. 1 

 (Chamaecyparis lawsonia. 1 



1 Damping-off not serious. 



2 Attack not serious except with fall-sown western yellow pine and Douglas fir. 

 ' Worse in fall-sown than in spring-sown beds. 



4 Not affected by damping-off. 



At nearly all Forest Service nurseries damping-off has not been 

 particularly virulent, whether because of properties of the soil or 

 not is unknown. When it has appeared, the most general method 

 practiced for its control has been simply to expose the beds to full 

 sunlight and, where practicable, to stir the surface soil. The spread 

 of the fungi is promoted by damp, warm soil and weather, although 

 Rhizoctonia and Pythium attack seedlings even in rather cool, damp 

 weather. The effect both of exposing the soil to the "sun's rays 

 and of stirring or cultivating it is to dry it out and thus produce a 

 condition unfavorable to the further development and spread of the 

 fungi. 



An effective method of control has been worked out by Hartley x 

 and Pierce at a number of nurseries. At the Bessey Nursery, 

 where damping-off has at times been very serious, commercial sul- 

 phuric acid is applied to the beds immediately after the seeds are 



1 Hartley, Carl, and Pierce, Ray G. " Control of Damping-off of Coniferous Seed- 

 lings." U. S. D. A. Bui. No. 453. 



