Spraying 



to be infected with fungus diseases or with fungus 

 spores, with the object of killing them. The princi- 

 pal substances used are hot water, copper sulphate, 

 formaMn, and hydrogen peroxide. The hot water 

 and copper sulphate methods are used almost 

 entirely in treating farm seeds, and we need not 

 consider them further. Formalin is used in treating 

 both seeds and tubers, hydrogen peroxide in treating 



(a) Formalin Treatment. — A solution of 1 part 

 of formalin ( =40 per cent solution of formaldehyde) 

 is made in 200-300 parts of water. The seeds or 

 tubers are steeped in this solution for two hours. 



(6) Hydrogen Peroxide Treatment. — ^The seed is 

 steeped to two hours in the fuU strength hydrogen 

 peroxide (20 vols.) and rinsed in clean water. The 

 half strength (10 vols.) may be used. It is usually 

 convenient to dry the seed before sowing. 



7. Dusting or spraying plants with a poisonous 

 substance so that spores, falling on the plant and 

 commencing to germinate, will come in contact with 

 it and perish. Sulphur and copper compounds are 

 generally most effective. The former are used 

 against mildews, as they tend to destroy the external 

 mycelium which these fungi form. 



All sprays, whether dust or liquid, should be applied 

 in a state of very minute subdivision, and when the 

 sun is not bright ; an endeavour should be made to 

 cover all parts of the plant completely. 



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