MISCELLANEOUS INSECTICIDE INVESTIGATIONS. 35 



Arsenate of lead, kerosene emulsion, and lime-sulphur in com- 

 bination is an incompatible mixture, usually causing severe injury to 

 the foliage. The calcium of the lime-sulphur breaks down the soap 

 of the kerosene emulsion, forming an insoluble calcium soap. The 

 result is that free kerosene is released in sufficient quantity to cause 

 foliage injury. 



A combination of lime-sulphur and kerosene emulsion, 10 per cent, 

 was tested on apple in the cluster-bud stage to determine the extent 

 of damage likely to occur. The plat which later received one-fourth 

 pound to 50 of powdered arsenate of lead was used for the test. Both 

 the foliage and unopened blossoms were so seriously injured as to 

 reduce materially the size of the crop. 



By reference to Table XVII the effect upon the crop yield will be 

 noted. All plats in this table having five count trees were sprayed 

 with lime-sulphur alone during the cluster-bud stage except Plat I. 

 Plat I, which was sprayed with the combination of lime-sulphur and 

 kerosene emulsion, yielded 7,588 apples (39 bushels); Plat II, 27,507 

 apples (109.5 bushels); Plat V, 27,658 apples (118 bushels); Plat VI, 

 32,567 apples (128.5 bushels). The number of bushels represents the 

 amount of fruit picked from the trees at harvest time. An estimate 

 of the loss of crop per tree due to the application of lime-sulphur and 

 kerosene emulsion is approximately 16 bushels, or, in other words, 

 the normal crop yield was reduced to about 33 per cent of that 

 from the lime-sulphur plats alone. 



Lime-sulphur and soap in combination is likewise impracticable, 

 since a calcium soap is thrown out, thus weakening the value of 

 each material. 



Diplumbic arsenate of lead, especially the powdered form which is 

 chiefly diplumbic, is likely to cause foliage injury when combined 

 with an alkalin solution, such as sodium sulphid. But when com- 

 bined with lime-sulphur some calcium arsenate is formed. This is 

 comparatively insoluble, and hence the possibility of burning is 

 reduced. 



Experiment XX. 



COMPARISON OP SODA, POTASH, AND SULPHUR SPRAYS AGAINST THE SAN JOSE SCALE. 



The pear orchard owned by Mr. John Hamilton, of Benton Harbor, 

 Mich., was used for the San Jose scale insecticide investigations. 

 This orchard consisted of 209 trees about 15 years of age. Four 

 varieties, planted in separate rows, were represented as follows: 

 Three rows of Bartlett, one row Clairgeau, three rows Beurre d'Anjou, 

 and one row Seckle. This orchard had been more or less neglected 

 for several years and was accordingly quite uniformly infested with 

 the scale. The orchard was divided into nine plats so as to include 

 all varieties in each plat, so far as possible. Trees were left un- 



