The Spraying of Trees. - 377 



fruit buds break open, but before the flowers expand (see illustration 

 on page 567), and again just as the last blossoms fall. In both cases 

 I should use a combination of Bordeaux mixture and Paris green. 

 The first spraying is for the scab fungus in particular, and for this 

 the Bordeaux is used ; but the Paris green will most likely be of 

 service in destroying various leaf-eating insects. The second spray- 

 ing is for the codlin-moth in particular, and for this the Paris green 

 is used ; but the Bordeaux mixture will still be needed for the apple 

 scab and other fungi. Whether or not it is necessary to spray again 

 will depend largely upon the season. The operator must watch 

 matters closely, and spray when he needs to do so or when he is in 

 doubt. Two sprayings are sufiicient for the codhn-moth, and three 

 are generally sulhcient for the apple-scab. These two sprayings 

 which I have recommended constitute the insurance which has 

 already been mentioned ; thereafter, the grower will be able to see 

 more definitely just what is needed. At any time when the tree is 

 in growth, Paris green or London purple should be used with lime, 

 or, better, with Bordeaux mixture, to prevent injury to the foliage. 

 One pound of Paris green to 2U0 gallons of water is the most ser- 

 viceable general formula for that material ; and to this a pound or 

 two of lime may be added. 



9. How can one tell if soluble arsenic is present in Paris green ? 

 It is the soluble arsenic which burns the foliage. This is always 

 present in London purple, but good Paris green should have little of 

 it. Farmers are always asking how they can determine if Paris 

 green contains soluble arsenic. This may be determined by the use 

 of the sulphur test. This test consists in adding sulphuret of 

 hydrogen to a solution of the poison, when, if arsenic is present, a 

 yellow precipitate will be thrown down. 



In a bottle holding five or six ounces, place a quarter of a tea- 

 spoonful of Paris green. Add water until the bottle is nearly full, 

 shake well, and then allow the material to settle. The clear liquid 

 which remains on top will contain what soluble arsenic may be pres- 

 ent. Carefully turn off this clear liquid into a long slender bottle or 

 test tube, add two or three drops of muriatic or sulphuric acid, then 

 add a tablespoonful or more of the solution of sulphuret of hydrogen. 

 If any arsenic is present in the clear liquid, a yellow discoloration 

 will at once appear, and if the liquid is allowed to stand for a few 

 minutes, patches or grains of a sand-like material will settle to the 

 bottom. This yellow precipitate is sulphide of arsenic. If very 



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