90 



COMPATIBILITIES OF COMMON INSECTICIDES 



]\Iany pests of fruit trees pursue their injurious activi- 

 ties at similar j^eriods of time, and some of tliem are jointly 

 susceptible to a single application of an insecticide or to 

 the same combination of spraying materials. As the ex- 

 pense for insecticides is usually much less than the cost of 

 labor and team, it is desirable from the standpoint of 

 economy of time, to reduce the number of applications to 

 the minimum. One means to this end is to employ com- 

 bination mixtures or, as they are popularly called, "two-in- 

 one" or "three-in-one" sprays, according to the number 

 raid nature of constituents contained in them. However, 

 not all substances that enter into the composition of insecti- 

 cides may be mixed together indiscriminately without 

 clanger of mutual destruction. This raises the point that 

 insecticides show great variations in degrees of compatibil- 

 ty. Following tlie initline liy Gray (Monthly Bui. Cal. Hort. 

 Com. HI, pg. 265, lOM) the results from mixing the more 

 common insecticides mtiy be briefly stated as follows: 



Better results by mixing — Paris green with bordeaux 

 mixture; arsenate of lead with bordeaux mixture; tobacco 

 with emulsions or soaps. 



Properties not changed by mixing — arsenate of lead 

 (acid) and tobacco; arsenate of lead (neutral) Avith bor- 

 deaux mixture, or tobacco, or soaps ; lime-sulphur with 

 tobacco ; tobacco with soap or oil emulsions. 



Efficient, non-injurious — arsenate of lead (neutral) with 

 lime-sulphnr ; soap iiud tol)acco. 



Inefficient, non-injurious — lime-suliihur Avith soap, or 

 ^•Ikalies or acids. 



Dangerous — Paris green with lime-sulphur, or soaps, or 

 oil emulsions; lead arsenate (acid) with soaps, or emulsions, 

 or alkalies; enudsions with lime-sulphur; zinc arsenate with 

 lime-sulphur, soaps or emulsions. Dangerous combinations 

 that are being tried by some growers today are arsenate of 

 lead or paris green with crude carbolic acid emulsions or 



