56 DISEASES OF CULTIVATED PLANTS 



Potassium sulphide solution. This is commonly known as 

 'liver of sulphur,' and is often of use for checking the exten- 

 sion of a disease. It is of most use in houses and small 

 batches of plants, but has no staying power on the foliage. 

 Potassium sulphide, . . . i oz. 



Water, . . . . 2 to 3 galls. 



The strength of the solution depends on the relative hardness 

 of the foliage, and must be carefully tested. If used too 

 strong the foliage will undoubtedly be scorched. 



This solution loses strength by standing, and should not be 

 prepared before it can be used at once. 



Potassium Permanganate. This is a useful fungicide at 

 times for plants under glass, as it checks the progress of 

 disease, and produces no discoloration of the foliage. It 

 discolours paint. The material should be purchased in the 

 form of crystals, which readily dissolve in cold water. A 

 pale rose-red solution should be used. 



Copper sulphate. This salt used in the proportion of i lb., 

 dissolved in 25 gallons of water, is an excellent winter 

 wash for fruit-trees that have suffered from any fungal disease. 

 The trees and surrounding ground should be thoroughly 

 drenched. It is most important to remember that this wash 

 should not be applied after January, as it completely destroys 

 the foliage, and all spraying should be done before the leafbuds 

 begin to swell. 



Formalin. This is a commercial name for a forty per 

 cent, solution of formic aldehyde in water. It is valuable in 

 destroying spores adhering to seeds, bulbs, tubers, etc., in the 

 proportion indicated under the respective headings. 



One pint of formalin in 30 gallons of water is a good 

 proportion to use for soaking * seed potatoes ' as a remedy 

 against the various forms of scab. The tubers should remain 

 in the liquid for two hours. 



For sprinkling grain to prevent smut, etc., use i pint in 

 50 gallons of water. Sprinkle the grain, mixing it at the 

 same time, and leave in a pile for some hours. 



Sulphur. This is used in the form of a fine powder, and 

 is one of the oldest of fungicides. It is most effective 

 against the superficial mildews belonging to the Peri- 



