SEED TESTING 5! 



78. Damping-off is a nurseryman's and gardener's term 

 for the decay of seedlings and cuttings, more especially 

 just above the surface of the ground. The conditions 

 that favor it are excess of moisture in both soil and air, 

 higher temperature than necessary for normal plant de- 

 velopment, and poor light. The weak plants that develop 

 under these conditions succumb to tiny fungi which live 

 upon decaying vegetable matter in the soil, and which 



FIG. 42 FRAMES FOR STRAW MAT MAKING 



These are homemade contrivances. Nursery and greenhouse supply houses make 

 mats by machine. 



live for months in spite of drouth or of frost. Should 

 damping-off be noticed the healthy plants should be 

 pricked out (81) or transplanted in fresh soil to save 

 them if possible. So rapidly does the trouble spread that 

 thousands of seedlings or of cuttings may be lost in a 

 single night. Perfect drainage in open soil with ample 

 watering and fresh air are partial safeguards. Steam 

 sterilization (Fig. 40) of the sand for several hours is 

 often done with good results. Damping-off frequently 

 follows copious watering of a bed which has been very 

 dry longer than advisable. 



The fungi usually believed to cause damping-off are Phytophthora 

 omnii'ora (Fusarium sp.), Pythium debaryanuui; but V. Peglion, an 

 Italian investigator, has identified several others Botrytes cinerea, 



