THE CONTROL OF DAMPING-OFF 109 



of an ounce produced no injury and reduced losses by damping- 

 off to less than i per cent. 



On a soil with a high carbonate content, evidenced by a 

 vigorous effervescence when the acid was applied, the method 

 was found to be ineffective. On this soil the use of copper 

 sulphate, one-fourth of an ounce per square foot, gave good re- 

 sults. This substance was applied in the same way as the acid, 

 and the same precaution to avoid chemical injury was found 

 necessarj'. 



An interesting indication was given by the experiments of 

 the effectiveness of cane sugar, 2| oz. to the square foot, in the 

 control of damping-off. The authors point out that, if some 

 unrefined sugar-bearing substance were available, it is possible 

 that for certain soils the application of sugar would become an 

 economically satisfactory treatment. Experiments on this 

 subject might well be carried out in the West Indies. 



There are secondary advantages to be expected from sul- 

 phuric acid disinfection which may be of considerable impor- 

 tance in some cases. Under appropriate circumstances a larger 

 germination percentage is secured, the number of parasites in the 

 soil is reduced and the well-known effect of disinfection on fer- 

 tility results in increased growth. Another valuable effect has 

 proved to be the reduction of weeds owing to the greater sus- 

 ceptibility of their seeds. Similar advantages are secured from 

 steam treatment. 



Some hints are given as to the method of handling the acid. 

 It should always be dissolved by pouring it into the water, 

 reversing the process may cause a serious accident. The solu- 

 tion should be made up in wooden or earthen containers and 

 applied with watering cans which have been coated inside with 

 paraffin wax. Boots may be protected by being heavily greased. 

 Wooden containers should be washed out, immediately after 

 use, with water containing washing soda. 



In respect of sterilisation methods generally note should be 

 taken of the evidence which has recently come in from several 

 directions that the condition of sterilised soils favours their more 

 rapid and complete infestation with the parasites concerned when 

 reinfection takes place. 



With herbaceous seedlings it is usually quite vain to apply 

 fungicides to the affected plants, but in the case of lime seedlings, 

 which are very subject, among other seedling troubles, to damp- 

 ing-off in the seed drills during wet and cloudy weather, it has 

 commonly been found practicable to save a large proportion of 

 the plants by a dusting process. A mixture of equal parts of 

 finely powdered sulphur and lime is used for this purpose, and 

 success depends on the promptness of its application when the 

 first signs of trouble appear. 



