38 MISC. PUB. 526, U. S. DEPT. OF AGRICULTURE 



Sodium lauryl sulfate is a white granular or flake-like material. It 

 may also be obtained in a paste form. 



With the exception of sulfonated vegetable oils, the above materials 

 are preferable to soap when used with hard water. 



These wetting or spreading agents are useful in getting into sus- 

 pension certain insecticides which are difficult to wet with water — 

 for example, in making spray suspensions of powdered derris or 

 cube root. Like soap, these materials increase the effectiveness of 

 certain contact sprays by improving their wetting qualities. They are 

 sometimes used in the preparation of "rotenone" dusts. 



Numerous proprietary protein spreaders are available for use in 

 obtaining more uniformly distributed deposits of lead arsenate and 

 other stomach poisons, with which this class of material is generally 

 used. If such materials are used, the manufacturer's directions 

 should be followed. Soybean flour, wheat flour, blood albumin, and 

 powdered skim milk are examples of protein spreaders. 



When spreaders are used with stomach poisons there is danger of 

 reducing the deposits to too thin a film if excessive quantities are 

 employed. For example, from V4 to y 2 pound of soybean floilr per 

 100 gallons is usually adequate. 



Stickers, or adhesives, such as oils or glue, which may have some 

 spreading action, are sometimes added to make the insecticide adhere 

 to the foliage. These materials are often used with lead arsenate 

 and other stomach poisons sprayed on ornamentals and trees to in- 

 sure a better and more lasting coverage of the plant surfaces, but 

 they are little used on vegetables. 



ZINC ARSENITE 



The domestic manufactured product, known as zinc arsenite, 

 usually considered as containing Zn 3 (As0 3 ) 2 and an excess of zinc 

 oxide, is a white powder which is colored pink for the insecticide 

 trade. It is nearly as toxic to insects as paris green and ranks close 

 to lead arsenate in adhesiveness. The arsenic content is equivalent 

 to about 40 percent of arsenic trioxide (As 2 3 ). Except under cer- 

 tain conditions this material cannot be applied to plants with tender 

 foliage, since arsenical burning results. It has been used for con- 

 trolling chewing insects on potato, and in Colorado it is used, at the 

 rate of 2 pounds to 100 gallons of spray, for the control of the Mexican 

 bean beetle. 



Caution. — Zinc arsenite is a very poisonous compound and must 

 be clearly labeled and stored away from all food products. 



PREPARATION OF SPRAYS AND DUSTS 



Dusts and sprays usually contain a relatively small proportion of 

 the killing agent, or insecticide. The greater proportion of most 

 dusts consists of carriers or inert materials which give bulk to the 

 mixture and permit a more uniform distribution of the insecticide. 



In preparing sprays, small quantities of insecticide are added to 

 water. Often other ingredients are included to increase the spread- 

 ing and sticking qualities and thereby the effectiveness of the active 

 ingredients. When preparing sprays, carefully follow directions. 





