can be controlled 



By WILLIAM L. DORAN* 



DAMPING-OFF is a kind of 

 juvenile plant disease, one of the 

 most common causes of the death 

 of young plants. Later, as plants 

 grow older, they are less susceptible 

 to this disease and finally relatively 

 immune. 



Seedlings that damp off decay 

 and shrivel near the base, topple 

 over, and die. This type of damping- 

 oflf, after seedlings emerge from the 

 soil, is called post-emergence damp- 

 ing-ofT. 



Damping-ofT may also kill seeds 

 or seedlings before germination or 

 before emergence of the seedlings 

 from the soil. This type of damping- 

 ofT is known as pre-emergence 

 damping-ofT and is controllable by 

 the same methods that are effective 

 against the post-emergence phase of 

 the disease. 



Fungi to Blame 



Damping-off is usually more se- 

 vere on plants in soil that is too 

 wet and in air that is too moist. 

 But water is not the real or first 

 cause of the disease. Plants damp 

 off because they have been attacked 

 by any one of several parasitic fungi 

 that live in the soil, and these fungi 

 do more damage and cause more 

 injury in a soil too heavily watered. 



It is easier to prevent damping- 

 ofT than it is to cure it; for the 

 disease is not readily controllable 

 if no protection is attempted until 

 after symptoms of the disease have 

 appeared, that is, after seedlings 

 have begun to damp off". Under 

 such circumstances, watering lightly, 



* Research Professor, Botany 



keeping the soil somewhat dry, helps 

 some but often not enough. 



Fungicide Gives Good Control 



I'he severity of damping-ofT, es- 

 pecially of the pre-emergence type, 

 will be lessened if seeds are sowed 

 in moderately dry soil containing 

 water to the extent of not more than 

 30 percent of its water-holding 

 capacity and if such soil is not wa- 

 tered for the first time until three 

 to five days after seeding. It appears 

 from this and other evidence that 

 some seeds can germinate in soil 

 too dry for infection by some fungi. 

 More complete control, however, is 

 accomplished by applying a fungi- 

 cide to the soil, usually before seed- 

 ing or, in the case of formaldehyde, 

 immediately after seeding. 



Common Vinegar Effective 



Vinegar contains about 4.0 per- 

 cent acetic acid, which may be used 

 as a soil fungicide. One-half pint 

 of vinegar, undiluted, applied to one 

 square foot of soil a few hours be- 

 fore seeding, with soils well watered 

 immediately after seeding, gives sat- 

 isfactory control of damping-ofT in 

 most soils. This treatment is usually 

 safe with cabbage, lettuce, tomato, 

 and several annuals including China 

 aster and Calendula; and. of course, 

 vinegar is often available when other 

 fungicides are not. 



Formaldehyde Also Protects 



Perhaps as easy a way as any to 

 improve germination of seeds and 

 stands of seedlings by protecting 

 them against damping-ofT is to wa- 



14 



