INSECTS AFFECTING PARK AND WOODKANIJ TREES 2)7 



tree with sulfur or other substance in order to render tlie sap distasteful to 

 insects of all kinds. This is a fascinating; theor\-, but has absolutely no 

 basis in fact. The safest way is to disregard all innovations till they have 

 been duly tested at experiment stations or are recommended by well known 

 authorities. 



Xccd of experiment. The following formulas comprise what are regarded 

 as the most reliable, but must be modified under varying conditions, to 

 meet tlie demantls of the occasion. It should be borne in mind that in 

 many cases it is not so much the insecticide used as the manner of its 

 application, though in some cases the difference is due to a variation in 

 composition. 



Foriiiiilas for arsenical preparations. Arsenate of lead ma)- be pre- 

 pared as follows : Dissolve i i ounces of acetate of lead (sugar of lead) in 

 four quarts of water and four ounces of arsenate of soda ( 50^'' purity ) in 

 two quarts of water, each lot in a wooden pail,and then add the solutions to 

 the required amount of water, which for most leaf-eating insects will be 

 about 50 gallons. This substance can be used in much greater strength 

 without danger of injuring the plants, provided it is properly prepared, and 

 though this poison does not act so rapidly as paris green and its allies, 

 it possesses superior adhesive powers, can be applied in much greater cjuan- 

 tities and its white color renders its detection on foliage very easy. It is of 

 special value against the elm leaf beetle because of its adhesiveness — it fre- 

 quently remains on the foliage nearly an entire season in spite of many 

 rains — and for this insect it is better to use the amounts given above in but 

 30 gallons of water. This poison has also been placed on the murket in a 

 paste form ready for dilution with water. Thus prepared it has all tlu- gooil 

 properties of the freshly made material and may be used with confidence. 

 The crystalline arsenate of lead can not be recommended as it is heavier 

 and does not adhere to the foliage as well as the other form. 



Paris green or london purple, and also certain other arsenical prepara- 

 tions, are used with great success in combating leaf feeders. One pound 

 of either of these poisons to 100 to 150 gallons of water is the [jroiiortion 



