DAMPING-OFF IN FOREST NURSERIES. 23 



beds. Making the upper part of the bed to a depth of several inches of 

 recently dug subsoil appeared effective in a single test by Spaulding 

 (137) and at four nurseries by coopenitors of the writer in later 

 tests, the results of which will be published elsewhere. The procedure 

 is unfortunately rather expensive in large-scale work and under some 

 conditions at least undesirable because of the poor subsequent growth 

 on such soil. Excessive vegetable matter (45), imperfectly rotted 

 manure (67), or green manures recently plowed under (43) have all 

 been advised against as likely to favor the disease. The experience 

 reported with conifers (67, 139) indicates that damping-off can be 

 to a certain extent decreased by broadcast sowing as compared with 

 sowing in drills. The usual recommendation of thin sowing to avoid 

 the seed-bed disease of other plants has also been made for conifers 

 (67). Transplanting healthy seedlings from infected beds into new 

 soil is recommended as a means of saving them from attack (11, 145). 

 The writer's tests of transplanting at a Nebraska nursery gave no 

 promise of economic value as a control method, although he is in- 

 formed that it was successfully employed in a nursery in New Mex- 

 ico. The time of sowing appears to have a relation to the amount of 

 disease at some nurseries, but conditions in this regard evidently 

 differ in different localities, so that 1 the best time to sow from the 

 standpoint of avoiding damping-off must be determined separately 

 by repeated tests at each nursery. For example, observations both 

 by the nurserymen and the writer during several seasons at the 

 Bessey Nursery, in Nebraska, indicate that fall sowing is an ex- 

 cellent means of decreasing loss from damping-off in at least one 

 pine species, and Retan (110) reports the same thing for a nursery in 

 Pennsylvania, while at two Kansas nurseries and at nurseries men- 

 tioned by Tillotson (139) fall-sown beds suffer more than those 

 sown in the spring. 



Treatment of the seed with mercuric chlorid (25) or with copper 

 sulphate (122) has been recommended. While it has been demon- 

 strated (38) that a proper heat treatment of the seed will greatly 

 decrease the damping-off in sugar-beet seedlings, this is explained 

 by the fact that one of the most important parasites of the sugar 

 beet is systemic and often present in the seed. There is no reason 

 to believe that seed-carried infection is of any importance in conif- 

 erous seed beds. The only advantage that could reasonably be 

 expected from a seed treatment of conifers would be that which 

 would come from the prevention of seed decay in the soil before 

 germination starts, and this protection could be expected to be ef- 

 fective only if a relatively insoluble disinfectant, such as Bordeaux 

 mixture, was used. 



Soil treatment is the most direct and probably the most profitable 

 method of attack on the disease. It is especially easy, for tobacco 



