CHAPTER XII 



THE CONTROL OF DAMPING-OFF 



Damping-off is the term applied to the failure of seedlings due 

 to their infection while in a tender state by certain soil-inhabiting 

 fungi. The reason for the name is the association of the trouble 

 with conditions of more or less excessive moisture, which favours 

 the development of the parasite at the same time that it in- 

 creases or prolongs the tenderness of the plants. Though not 

 necessarily confined to seedlings crowded in boxes or seed beds, 

 it is amongst such that the affection usually appears and, by 

 progressive infection, is able to cause extensive losses. 



The longer the soil of the seed-bed has been in use, and the 

 more decaying animal or vegetable material it contains, the more 

 likely it is to harbour fungi capable of causing damping-off. 

 Heavy water-retaining soils are more favourable to the affection 

 than those which are light and porous, and provision for rapid 

 drainage is one of the most important precautions against it. 

 Shade and shelter, by maintaining humidity, increase the ten- 

 dency to it ; in these respects, as in the supplying of water, the 

 conditions which may favour the seedlings favour the disease, 

 and a mean has to be struck between slow growth and loss. 



The trouble occasioned by damping-off in these islands is not 

 so great as might be expected by an agriculturist accustomed to 

 temperate countries, where warm, humid weather, such as is 

 associated with ideas of the tropics, is greatly feared in this 

 connection. 



In the first place nearly all the staple food plants — sugar- 

 cane, bananas, tannias, dasheens, sweet potatoes, yams, cassava 

 —are raised from cuttings of one sort or another, while cotton, 

 corn and pulses, which are raised from seed, are planted, a few 

 seeds together, in tneir permanent positions in the open ground. 

 Of agricultural as distinct from garden crops, tobacco, onions, 

 and limes, which are raised in seed-beds, have been the plants to 

 suffer most in the West Indies from the affection under notice. 



Merely reducing the density with which the seed is sown is 

 often sufficient to avoid or reduce the damage by permitting 

 increased ventilation, preventing the drawing up of the seedlings, 

 and making the spread of infection more difficult. Further 

 measures to this end are the use of sandy soil, of subsoil, or of a 

 surface dressing of sand or fine gravel, and the choice of an open 

 rather exposed situation for the seed-beds. The use of wood- 

 ashes or lime is not to be recommended. 



The one means so far discovered which can be relied upon to 

 give satisfactory results under any reasonable conditions is the 

 lo;^ 



