154 PEACH LEAF CURL: ITS NATURE AND TREATMENT. 



grower. For this reason the writer gives, on page 183 of this bulletin, 

 a simple way of preparing the copper carbonate on the farm at a 

 minimum figure.^ 



PREPARATION OF THE SULPHUR SPRAYS. 



While the use of copper sulphate as a base for sprays intended for 

 the control of fungous diseases is very general, there are special dis- 

 eases or combinations of diseases which may be more cheaph'^, and 

 often more successfully, treated with sulphur in the form of powder 

 or spray. The world-wide use of sulphur for the control of powdery 

 mildew of the grape is a well-known example. It is also known that 

 sulphur possesses valuable insecticidal qualities, and many of the scale 

 insects and mite diseases of our fruit trees may be readily controlled 

 by the use of sulphur so combined and prepared as to be applicable 

 as a spray. For many years the most successful and almost the only 

 treatment of the San Jose scale on the Pacific coast has been by sulphur 

 sprays. This scale is very injurious to peach trees, and the time for 

 the application of sulphur for its treatment is during the winter, at the 

 time of treatment for peach leaf curl, when the tree is dormant. It 

 has already been shown in this bulletin that such a winter treatment 

 of the peach tree with sulphur sprays will also control peach leaf curl. 

 For this reason, and the fact that the San Jose scale is constantly 

 spreading throughout the East, much attention is here given to the 

 presentation of this form of spray, one application of which may con- 

 trol two serious diseases. Experiments conducted by the writer have 

 shown that the pear leaf mite may be controlled by the winter use of 

 sulphur sprays, and it is thought probable that their use will also con- 

 trol the oyster-shell bark louse of the apple, which has become almost 

 a scourge over much of the East and in the Pacific Northwest. 



As in the case of copper sulphate spraj's, it has also been found 

 that the sulphur sprays may be most satisfactorily prepared by com- 



' In view of the work of ]Mr. C. L. Penny, published in Bulletin 22 of the Delaware 

 Agr. Exp. Sta., 1893, the amount of water recommended to he added before the strong 

 ammonia water is poured upon the carbonate of copper is nmch greater than formerly 

 used by the Department. Mr. Penny conducted a somewhat extended series of 

 experiments to ascertain the solubility of copper carbonate in ammonia gas as it is 

 contained in ammonia water of different strengths. He found that a given amount 

 of ammonia gas in a weak solution of ammonia water dissolves more copper than the 

 same amount of gas in a strong solution. A given weight of ammonia gas in a 2 to 4 

 per cent solution of ammonia water dissolves more copper carbonate than an equal 

 weight of gas in either a weaker or stronger solution. The gas in a 2 to 4 per cent 

 ammonia water will dissolve its own weight or more of copper carbonate. On the 

 other hand, the ammonia gas in a 10 per cent solution of ammonia water will dis- 

 solve but 60 per cent of its weight of copper carbonate, and ammonia gas in a 20 per 

 cent solution dissolves only about 35 per cent of its weight of copper. Furthermore, 

 the ammonia gas contained in ammonia water of less than 2 per cent strength rapidly 

 loses its power to dissolve copper carbonate as the solution is weakened. 



