THE HOWARD SCALE 15 
In the spring of 1906, in the orchard section of the Grand valley, 
a carload of 30,000 pounds of Rex was used experimentally as a spray 
principally against this insect, and in the spring of 1907 five car 
loads were shipped into the above section for use against this and 
other orchard pests. Upon Howard scale results have been satis¬ 
factory. 
The spray has the disadvantage, as a commercial product, of being 
subject to variation in strength without knowledge of the consumer. 
The orchardist compounding his own spray material may feel more 
confident of his product. 
The Rex mixture was to be had the past season by growers at 
Grand Junction for 25 cents per gallon, making the cost of 200 gallons 
of spray of the recommended formula about $5.70, or a trifle less than 
3 cents per gallon. 
Lime: and Sulfur Mixtures. The lime and sulfur wash mixed 
in the right proportions, properly boiled and correctly sprayed is the 
most satisfactory spray thus far used against Howard scale. 
Lime and' sulfur was originally a stock dip used in California 
and was first demonstrated to be of value as an insecticide in 1886.* 
It was then taken up as a scale treatment in the East and is now very 
widely used and considered the standard scale remedy. It is also 
valuable as a dormant tree spray against many other insects and is 
of known fungicidal value, controlling the peach leaf curl of some 
states. 
Different formulas have been adopted in different states. Some 
recommend slightly more lime than sulfur in order to insure the com¬ 
bining of all sulfur. Others contend that equal parts of lime and 
sulfur are best when a strong quick lime, high in calcium, is used. 
The belief that equal portions of lime and sulfur, as a rule, produce 
as strong a solution, chemically, as is possible to secure, is endorsed 
in a recent bulletin by J. R. Haywood of the Bureau of Chemistry* 
The addition of salt formerly recommended may be safely discontinued. 
It adds nothing to the killing effect of the spray, increases cost, makes 
the spray more unpleasant to use and harder upon machinery. The 
addition of copper sulphate (blue vitriol) to the formula has been 
recommended by some experiment stations, by others it is considered 
without insecticidal value,* and by some it is regarded as a positive 
injury to the insecticide properties of the spray.* 
Variety of practice in the preparation of the spray is to be found. 
All methods provide for chemical union between lime and sulfur 
brought about by heating with water. The heat may be supplied 
in a variety of ways externally and the spray has been made by heating 
with caustic soda, potassium sulfide or an increased amount of Quick 
lime. 
The so-called self-boiled lime-sulfur-soda wash used in the experi- 
* Bulletin No. 166, Calif. Agr. Exp. Sta., 1905. 
Bulletin No. 101, Bur. of Chem. U. S. Dept, of Agr., Feb., 1907. 
* Ill. Agr. Exp. Sta. Bulletin No. 107, 1906. 
* Wash. Agr. Exp. Sta. Bulletin No. 76, 1906. 
