1920.] " Damping off " of Tomato Seedlings. 671 



present in several instances. Further work is being done in 

 this direction, but in the meantime the importance of a pure 

 water supply cannot be too strongly emphasised. 



All precautions should be taken to avoid the wells being 

 polluted by surface drainage from the nursery or any adjoining 

 allotment or garden. 



Many samples of seed have been examined, but in no case 

 up to the present have the " Damping off " organisms been 

 found on the seed. 



Experimental Tests. — Different methods of making seed 

 beds, sowing seeds, watering, &c, have been investigated to 

 ascertain the relation of these operations to the incidence of 

 the disease. A covering of sand, charcoal or lime either alone 

 or above a covering of sterile soil produced only a small increase 

 or decrease in the amount of disease. Charcoal had no effect 

 when used alone as a covering to the seeds, while sand 

 reduced the amount of diseased seedlings by 20 per cent. 

 Five per cent, of charcoal mixed with the soil had a distinctly 

 beneficial result ; in addition to reducing the amount of 

 disease, a fine crop of sturdy dark green seedlings was produced. 

 In the case of lime, it was found that whether mixed with the 

 soil or added as a covering to the seeds, this constituent 

 apparently caused an increase in the amount oi disease. 



Sowings of seeds closer than 50 per box (14 in. by 9 in. 

 'by 2 in.) should be avoided, as the practice materially assists 

 the spread of the disease. 



Watering in the morning or evening is preferable to perform- 

 ing this operation at midday, while bottom watering, by 

 standing the boxes in a shallow tray containing water half an 

 inch deep for five minutes, is preferable to top watering. 

 Dressings of nitrate of soda or superphosphate were found to 

 have little effect upon the amount of disease, but half an ounce 

 of sulphate of potash added to 5 Lb. of soil resulted in a consi- 

 derable reduction of the pest. 



Many fungicides were tried, but only one gave any success, 

 viz., a mixture of 10 parts of lime and 1 part of copper sul- 

 phate. Dry powdered liine, obtained by slaking caustic lime, 

 and ground copper sulphate, were thoroughly mixed and spread 

 over the surface of the soil at the rate of f oz. per square foot, 

 and disease on plants grown on this soil was reduced from 

 47 per cent, to 7 per cent. 



A relatively high percentage of moisture in the soil and the 

 air favours the rapid spread of the disease. Careful regulation 



