4 MASS. EXPERIMENT STATION BULLETIN 394 



Table 1, based on that work and on other observations, especially as regards 

 safety or freedom from chemical injury, consists of a list of vegetables together 

 with the materials which, when used for the treatment of their seeds, resulted in 

 the least damping-ofif and the best stands of each. Some show a decided prefer- 

 ence for one chemical, e.g., celery and parsnip for zinc oxide. In the case of other 

 vegetables, differences between results with two chemicals were not great enough 

 to prove that there are preferences. 



Treatments of seeds of beet, spinach, Swiss chard, tcmato, endive, lettuce, 

 cucumber, summer squash, and muskmelon usually gave results inferior to those 

 secured by formaldehyde treatment of the soil; either method satisfactorily pro- 

 tected pepper, celery, and chicory; and seed treatments often gave better results 

 than formaldehyde treatment of the soil with eggplant, onion, dandelion, and 

 especially crucifers. 



Treatment of the seeds of such vegetables is important, especially where there 

 is a scarcity of seeds, where seeds are sown in the field, or where soil disinfestation 

 is not feasible. As far as possible, growers will do well to keep in stock all of the 

 chemicals^named in Table 1 and to follow the recommendations which are therein 

 made. 



TREATMENTS OF SOILS 

 Chlorpicrin Emulsions 



Chlorpicrin is sometimes injected into soil for the prevention of damping-off 

 but, because of the danger of injury to plants, such applications must be made 

 long before seeding. As used here, Larvacide chlorpicrin emulsion^ and Seido- 

 rin chlorpicrin emulsion^ were applied to soil (0.64 to 1.0 cc. in 0.8 quart water 

 per square foot) Immediately after seeding. Seidorin, 1 cc. per square foot, gave 

 good results with beet, cabbage, lettuce, pea, pepper, and spinach (see Table 2). 

 Damping-off of these vegetables, and of broccoli and cucumber, was also well 

 controlled by Larvacide chlorpicrin emulsion similarly used. Thus applied, 

 immediate!}' after seeding, best results were generally obtained, however, by the 

 use of Larvacide chlorpicrin emulsion 0.64 cc. or Seidorin chlorpicrin emulsion 

 0.76 cc. per square foot, greater concentrations or heavier applications being 

 often injurious. 



When applied at the rate of 1 gallon to 30 feet of row after sowing seeds of pea 

 but before covering them, Larvacide chlorpicrin emulsion 1:1000 markedly im- 

 proved the stands (see Table 9), g'ving as good results, in fact, as did formalde- 

 hyde. 



Used in these ways, chlorpicrin emulsions are certainly effective against damp- 

 ing-off. But, on grounds of convenience and practicability, they are not pre- 

 ferred by the writers for the control of this disease. It is difficult to secure uniform 

 dilutions and, hence, to make uniform applications; and the fumes of chlorpicrin 

 are, moreover, decidedly unpleasant. 



Acetic Acid and Vinegar 



Acetic acid, worked into soil before seeding, has been successfully used for the 

 control of damping-off (4)^. 



Applied to the surface of soil after seeding, glacial acetic acid, 1.5 to 2.5 cc. in 

 0.8 quart water per square foot, gave good results with lettuce, pepper, spinach, 

 beet, chicory, dandelion, endive, cabbage, and cauliflower (see Tables 2 and 10). 



-From Innis Speiden and Co. It contains 70 percent chlorpicrin. 

 ^Frorn Japan Seed Co. It contains 45 percent chlorpicrin. 

 'Numbers in parentheses refer to literature cited, page 20. 



