Diseases and Pests of the Apple and Their Control, 241 



calcium arsenate is cheaper pound for pound than lead and 

 this may cause its ultimate introduction in the East where 

 codlin-moth infestation is not the menace which it is in 

 most irrigated regions. Calcium arsenate is still in the 

 experimental stage. 



Arsenite of zinc is a quick-acting poison which in pow- 

 dered form contains about 40 pef cent arsenic-oxide. It 

 is used in tussock moth control in the Pajaro Valley or 

 Watsonville district, California, hut on account of its tend- 

 ency to burn it has not been employed elsewhere. 



For sucking insects, contact sprays. 



Liquid lime-sulfur has become the standard dormant or 

 winter spray for apples. It is a combination insecticide 

 and fungicide chiefly valuable for its effectiveness against 

 San Jose scale and certain other insects as well as against 

 fungous diseases. It is to be preferred to any of the 

 present forms of so-called dry lime-sulfur. For full win- 

 ter strength, 1 to 8 is generally accepted as the proper rate 

 of dilution. This rate applies to the concentrated com- 

 mercial lime-sulfur testing 33° Baume. Weaker solu- 

 tions should be diluted accordingly. The table of dilu- 

 tion on the next page will serve as guide. 



For summer sprays, particularly for apple-scab, a weak 

 solution of lime-sulfur is widely employed alone or in com- 

 bination with nicotine and arsenate of lead. The strength 

 at which summer applications of lime-sulfur cause burning 

 varies with the season and the climatic conditions. Lime- 

 sulfur has been used 1 to 10 in summer without injurious 

 effects to the fruit or foliage. Again a dilution of 1 to 30 

 may cause foliage burning. It is generally accepted that 

 1 to 35 for the pink spray and later summer application 



