DAMPING-OFF IN FOREST NURSERIES. 



13 



of seedlings which succumbed to damping-off after emergence were 

 reduced to a percentage based on the indicated number of viable seeds, 

 and they are directly compared in columns 6 and 7 of Table I. At 

 three of the nurseries the data of the same species of pine and with 

 the same treatment were averaged. 



The data in Table I do not indicate any regularity either in the 

 extent of loss before emergence, the loss after emergence, or in the 

 ratio between these 

 two values. For ob- 

 vious reasons, no reg- 

 ularity is to be ex- 

 pected in any of these 

 items. The table is 

 of some interest, 

 however, in confirm- 

 ing the evidence of 

 the inoculation ex- 

 periments, of obser- 

 vation of sprouting 

 seed dug up in the 

 beds, and of the par- 

 tial or complete fail- 

 ure of emergence at 

 the centers of large 

 damping-off foci 

 (figs. 4, 7, and 8) that 

 the work of parasites 

 before the seedlings 

 appear may in some 

 cases be of consider- 

 able importance. It 

 is obviously impos- 

 sible to make any 

 general quantitative 

 statement of the se- 

 riousness of such loss, 

 in view of the varia- 

 tion in its extent at 

 different times and 

 places and of the in- 

 accuracy of any computations based on the relative emergence 

 of hosts as irregular in their germination as the conifers are 

 known to be. The case is complicated in addition by the fact 

 that, despite careful avoidance of treated plats known to have 

 suffered chemical injury, it is probable that a few seedlings were 

 killed before emergence by the disinfectants used in some of the 



Fig. 6. — Root sickness in Pinus nigra poiretiana. The two 

 seedlings at the right are healthy. The three at the left 

 have had their taproots decayed to within 1J inches 

 of the soil surface. All are putting out lateral roots from 

 the lowermost sound point. Similarly injured seedlings 

 when transplanted lived and made satisfactory growth. 



