664 



Spraying Mixtures. 



[FEB., 



insect pests by that time will be showing on the trees, if they 

 are to appear at all. Many young caterpillars also will be killed 

 by this spraying. 



If, in spite of the operations just described, leaf-eating cater- 

 pillars are found to be infesting the trees, spraying with arsenate 

 of lead, 3 lb. to 100 gallons of water, may be necessary ; or if 

 scab is persistent on apples and pears, or leaf-blight on plums 

 treatment with Bordeaux mixture will be beneficial. 



Prescriptions for the preparation of lead arsenate differ slightly 

 in proportions of constituents. Dr. Dyer states that I lb. of 

 dry arsenate of soda to 3 lb. of acetate of lead would make 

 tribasic arsenate of lead, the actual quantity of which would be 

 lb. Both constituents should be of 98 per cent, purity. 

 They should be dissolved separately and mixed well. Simi- 

 larly, the quantity of arsenate of lead to 100 gallons of 

 water varies in different recipes. A Bulletin from Cornell 

 University says 2 lb. to 8 lb. Another prescription says 2 lb. 

 " or even more, as it does not hurt the foliage." An excessive 

 quantity of the poison is wasteful ; but, on the other hand, the 

 probable explanation of arsenate of lead having proved less 

 effective than Paris green in some cases, according to reports of 

 fruit-growers, is that it has been too much diluted. This poison 

 was first recommended for use in spraying in 1892 by Mr. F. C. 

 Moulton, an American chemist. When first tested, such weak 

 solutions as 6 oz. to 8 oz. to 100 gallons of water failed to kill 

 caterpillars quickly, while 1 lb. to i^ lb. were regarded as satis- 

 factory. No injury to apple foliage occurred in a trial of 16 lb. 

 of arsenate of lead to 100 gallons, but 3 lb. would be ample, 

 and as that quantity has been used in many trials recently,, it 

 may be recommended. To make this quantity, according to the 

 formula given above, 3} lb. of acetate of lead and 1 J lb. of 

 arsenate of soda would be required. 



In the article in the Journal for April, 1905, already referred 

 to, the difficulty of spraying with lime, sulphur, and soft soap, to 

 prevent birds from devouring the buds of gooseberries, was 

 noticed. This is one of the combinations which do not make 

 suitable spray-liquids, as a flaky soap of lime is formed, while 

 the sulphur also is brought out of such combination with the 

 lime as it had made by being added in thin layers while 



