422 CONTROLLING INSECTS AND PLANT DISEASES 



injury. Use one-third as much arsenite of zinc as we would of 

 arsenate of lead paste in the above formulas. 



Hellebore is a poisonous light brown powder. It is often 

 applied in the form of dry dust either alone or mixed with flour. 

 It must be fresh to be effective. This material is not recommended 

 because so much of the commercial product has lost its strength 

 before it is sold. As a spray four ounces of the fresh poison may 

 be mixed with three gallons of water. As its poisonous properties 

 disappear soon, it may be used instead of the arsenical sprays on 

 fruits or crops that are approaching maturity. 



Contact Insecticides. Lime-sulfur solution is now one of the 

 most common spray materials. It will smother scale insects, and 

 acts also as an effective fungicide. There are three main forms 

 of this in use: (1) concentrated lime-sulfur solution, (2) commer- 

 cial lime-sulfur solution, (3) self-boiled lime-sulfur. 



Concentrated lime-sulfur contains thirty pounds powdered 

 sulfur, fifteen pounds burned lime and fifteen gallons of water. 

 Start the lime to slaking and add the wet sulfur to it. Then add 

 the remainder of the fifteen gallons of water and boil until dissolved. 

 This may be kept in a closed vessel until wanted. A layer of oil 

 on top of the liquid will keep the air away sufficiently. For winter 

 spraying of apples this is diluted nine times its volume of water. 

 Before diluting the concentrated solution, find the specific gravity 

 of the liquid. Divide the decimal of this number by three hun- 

 dredths (.03), and the quotient will tell the number of times to 

 dilute the liquid. If the specific gravity of the boiled stock solu- 

 tion is 1.27, divide the .27 by .03 which gives us 9, and indicates the 

 number of parts of water to use. The winter spray for peaches 

 should be a little more dilute than this. 



An easy way of boiling the lime-sulfur solution is to use an 

 open kettle with a fire underneath. Sometimes a barrel or tank is 

 used, and the boiling is done with a steam pipe from a small boiler. 



Commercial forms of the concentrated lime-sulfur are offered 

 by many dealers. Usually the specific gravity is indicated on 

 each of these preparations or directions are given for the diluting 

 of the material for different purposes. 



Self-boiled lime-sulfur contains eight pounds powdered sul- 

 fur, eight pounds fresh burned lime in 50 gallons of water. The 

 principle involved in making this preparation is that the heat 

 produced by the slaking of the lime will be sufficient to dissolve 

 most of the sulfur. Place the lime in a barrel or wooden tub and 



