ARSENATE OF LEAD 197 



add enough water to make 50 gallons, strain into the spraying 

 cask and apply at once. Remember this is merely a summer 

 fungicide and has no value for San Jose scale and relatively 

 little as a dormant fungicide. 



Dry Forms of Sulfur Compounds. — At the present time the 

 most interesting of the special forms of sulfur on the market are 

 the dry forms in combination w^ith other substances such as 

 calcium, sodium and barium. They come as powders of varying 

 degrees of fineness and dissolve fairly readily in water. Some 

 of them are very promising and of course all have the advantage 

 over the liquid forms that they eliminate expense in handling. 

 If further experiments shall show they are efficient under all con- 

 ditions and do not injure foliage they ought to prove of value. 



''Atomic sulfur" is another form. This is a very finely 

 divided paste form of pure sulfur which seems promising, but 

 at the present writing needs further testing. 



INSECTICIDES 



There are two general classes of insecticides : The food-poisons, 

 used for chewing insects and of usually some form of arsenic; 

 and the contact sprays used for sucking insects. 



In the first of these classes, at the present time, the arsenate 

 of lead is used much more generally than any other form, with 

 Paris green as a second. Several others are on the market and 

 are used to a limited extent, but from the commercial orchard 

 standpoint they may be ignored. 



Arsenate of Lead. — The great advantages of arsenate of lead 

 are (1) that it is very adhesive, remaining on the leaves through 

 the entire season; (2) that it is finely divided, remaining in sus- 

 pension much longer than Paris green ; and (3) that it is usually 

 harmless to foliage. This is a strong combination and it is small 

 wonder that arsenate of lead is so generally used. It is, how- 

 ever, sometimes injurious to trees, and one should take every 

 precaution possible to avoid trouble 



There are two forms on the market, one of which, known as 

 the tri-plumbic foi-m, has a hisrher percentage of lead and no 

 hydrogen ; while the other, known as the standard, has a higher 



