INSECTICIDES 43 



the material or increase the danger of burning foliage so that it is 

 generally wiser to use the commercial product. 



7. Ar senile of zinc is another material which is occasionally 

 used as a substitute for lead arsenate. It comes in the commercial 

 form as a rather light powder. It has a tendency to burn foliage 

 but has good killing qualities. It may be used, if conditions de- 

 mand, with a fair degree of safety by combining it with bordeaux 

 mixture or with lime. It should not be used at more than half 

 the strength recommended for arsenate of lead. 



8. White arsenic is the basis for all the stomach poisons, at 

 least indirectly. It is cheap and a violent poison to insects but 

 on account of its complete solubility is not available as a spray 

 material. It is of value for use in poisoned baits and as a basis 

 for the preparation of other materials. 



9. Sodium arsenite is a cheap and effective insecticide, avail- 

 able for some uses. It is generally prepared by the user, the com- 

 mon Kedzie formula following: 



White arsenic 1 Ib. 



Sal soda 2 Ibs. 



Water 1 gal. 



Mix the arsenic into a paste with a little water and dissolve 

 the sal soda in the remaining water. Add the arsenic paste to the 

 soda solution and boil until the arsenic is completely dissolved. 

 Add water to make a full gallon and use at the rate of one quart to 

 fifty gallons of bordeaux mixture, being careful to see that the 

 bordeaux has an excess of lime. This material is not widely 

 used although in some regions it is the favorite spray for potatoes. 



10. Hellebore. The powdered roots of the white hellebore are 

 often used as an insecticide in place of arsenicals, especially for 

 currant worms, rose slugs, and similar saw-fly larva) and for insects 

 affecting crops soon to be eaten, as the hellebore is much less 

 poisonous to man and animals than arsenicals. It may be applied 

 dry, diluted with from 5 to 10 parts of flour, or as a spray, 1 ounce 

 to a gallon of water. It is too expensive to use except for a few 

 plants in the yard or garden, and like pyrethrum, deteriorates 

 with age and if exposed to the air. 



Harmlessness of Arsenicals when Properly Applied. The ques- 

 tion is frequently asked whether it is safe to apply arsenicals to 

 vegetables and fruits to be used as food. Where sprayed or dusted 



