DAMPING-OFF IN FOREST NURSERIES. 



11 



Something is already known about the seed fungi of herbaceous 

 plants (76, 91), broad-leaved trees (79, 92), and juniper (95). 



RELATIVE IMPORTANCE OF THE DIFFERENT TYPES. 



Of the types of damping-off described in the foregoing pages the 

 first two are ordinarily the most important. Late damping-off is 

 rarely as serious as the normal type of damping-off. Top damping is 

 only of importance in cases of excessive and unusual atmospheric 

 moisture, so far as the writer's experience indicates. In the Middle 

 West it has proved relatively insignificant. The three types which 



Fig. 5. — Nearly complete destruction of the seedlings of Pinus banksiana at an unusually 

 early age, at Garden City, Kans. (Photographed hy Dr. J. V. Hofmann.) 



occur after the seedlings appear above the soil surface can, of course, 

 be evaluated by frequent counts during the damping-off season. This 

 has apparently not yet been done by anyone. However, in experi- 

 ments on damping-off control by soil disinfection, data have been 

 obtained on comparative emergence (number of seedlings appearing 

 above the soil surface) in treated and untreated plats and on the total 

 parasitic losses after the seedlings appear which permit a certain 

 amount of analysis of the losses due to damping-off parasites. The 

 data from five nurseries bearing on this point are presented in 

 Table I; 



