CONTROL OF DAMPING-OFF 7 



good reason, to seed treatment with Semesan or zinc oxide and to soil disinfesta- 

 tion by other chemicals or by steam. 



The use of corrosive sublimate on soil immediately after seeds of crucifers are 

 sown is, in any case, no guarantee of good stands. A solution, 1 :1000, sometimes 

 gave good results with Brussels sprouts, but the number of seedlings of coUards 

 and kohlrabi which lived was increased more by seed treatment with Semesan 

 than by soil treatment with corrosive sublimate. 



Zinc oxide 0.5 ounce per square foot, applied as a dust to the surface of seed- 

 beds immediately after seeds are covered, has been recommended more as a 

 supplement to seed treatment than as a substitute for it (13). But zinc oxide so 

 used b}' other investigators was not very effective (15), and as used here with 

 lettuce was of no benefit. 



In another case, zinc oxide and Vasco, a zinc compound, were twice dusted 

 upon seedbeds, once immediately after the seeds were covered and again a week 

 later. This did not improve stands of lettuce at ?11, but it did improve stands of 

 cabbage more than did copper-lime dust. 



Zinc oxide, 0.2 ounce in 0.8 quart water per square foot of soil, improved the 

 stands cf lettuce and pepper less than did other treatments similarly applied 

 immediately after seeding; and Vasco thus used with the vegetables named in 

 Table 2 was not of significant benefit to any except lettuce and pepper. Zinc 

 oxide applied in water tends to cause the surface of the soil to cake and become 

 hard, and on the basis of results obtained by the writers, it is not recommended 

 for use in this manner. 



Useful as red cuprous oxide, Semesan, and zinc oxide are for the treatment of 

 seeds ot seme vegetables, it does net appear that there is much to be said for 

 them as soil disinfestants for the control of damping-cff. Then too, when applied 

 in water they settle out of suspension unless continually agitated. This makes 

 uniformity of application difficult and probably accounts for some of the injury 

 on the one hand and some of the failures to control en the other. 



Sodium Hypochlorite 



Chlorox and Oxol, each containing 5.25 percent sodium hypochlorite, did not 

 in most cases give as good results as other treatments of soil or seed. That is in 

 line with the results of Horsfall (13) in whose work Chlorox caused some injury 

 and failed to control damping-off satisfactorily. 



Stands of pepper seedlings were much less improved by Oxol (38cc. in 0.8 quart 

 water per square foot) than by formaldehyde. As may be seen by reference to 

 Table 2, Chlorox did not significantly improve the stands of nine out of the eleven 

 kinds of vegetables named. It did improve stands of lettuce and spinach but not 

 so much as did formaldehyde or Seidorin cr, in the case cf spinach, acetic acid. 



In controlling damping-off, solutions of Chlorox thus applied to soil were no 

 be*^ter than standard dry treatments of seeds of pepper and endive, and decidedly 

 less effective than standard dry treatments of seeds of beet, chicory, cabbage, 

 cauliflower, eggplant, and tomato. 



Salicylic Acid 



Salicylic acid can be used as a soil fungicide. When worked, without water, 

 into soil immediately before seeding, it usually increased the number of plants 

 which lived and there was no injury to beet or cucumber by applications up to 

 10 gm. per square foot (4). Damping-off was well controlled (See Table 4) by 

 5 or 6 gm. salicylic acid thus applied to soil immediately before seeding. There 

 was some injury to cress but not to beet or pepper. 



