1908.] Apple "Scab" or "Black Spot." 



i93 



requirement of the formula given above, before being mixed. 

 The " stock " copper sulphate solution must be measured 

 out in a copper or wooden receptacle. 



Only freshly-mixed home-made Bordeaux mixture should 

 be used. The various " dry Bordeaux mixtures " put on 

 the market are not nearly so efficacious and should be 

 avoided. 



A simple and reliable test as to whether the Bordeaux 

 mixture when made is safe to use as a spray on leaves and fruit 

 is obtained by the immersion in the fluid, for at least one 

 minute, of a bright blade of a knife. If at the end of that 

 time the surface of the blade is unchanged in appearance 

 the mixture is perfectly safe to use ; if, however, the surface 



fig 9. — Rot of Apples, caused by various "moulds" (appearing as white spots in 

 the photograph) which have gained an entrance through the skin of the apple at the 

 places where apple scab or " black spot" have occurred. 



of the blade becomes the colour of copper plate, the mixture 

 is unsafe to use, and more lime milk must be added until it 

 fails to give this reaction. 



If an insecticide is required, arsenate of lead* can be added 

 to Bordeaux mixture at the same rate per gallon as when 

 water is used. This addition will keep the leaves safe from 

 the attacks of all caterpillars. 



If, as sometimes occurs, an attack of " scab " appears 

 late in the season affecting the half -grown fruit, it is not advis- 

 able to spray them with Bordeaux mixture, as the fruit when 

 ripe would be marked with the bluish spots of the mixture. 

 These markings, unless they were washed off, would probably 

 affect the market value, although the slight trace of copper 



* Arsenate of lead is best obtained in the paste form. 



(3599) 



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