38 MISC. PUB. 526, U. 8S. DEPT. OF AGRICULTURE 
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 fiour, 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 14 to 14 pound of soybean flour 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 zine arsenite, 
usually considered as containing Zn;(AsO;), 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,O,). 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. 
