396 
JOURNAL OF ECONOMIC ENTOMOLOGY 
[Vol. 17 
THE USE OF SKIM MILK IN THE PREPARATION 
OF CERTAIN SPRAY MATERIALS 
By R. H. Robinson, Chemist, Oregon Experiment Station 
Abstract 
The advantages of using skim milk or milk powder in the preparation of certain 
sprays are discussed. A method is outlined for the use of milk in preparing a sub¬ 
stitute for the different sulfur sprays used as summer fungicides. A mineral oil 
emulsion that may be prepared by using skim milk, and hydrated lime as an 
emulsifier is described. The use of skim milk, any of the condensed milks, or milk 
powder as a spreader is emphasized. These products will improve the spreading 
properties of the spray as well as calcium caseinate, and at a much lower cost. 
The important requirements of a spray material are effectiveness 
without danger of injury to the plant or foliage, low initial cost, sim¬ 
plicity of preparation and facility of handling. Skim milk or the dried 
product is available at a reasonable cost in all sections of the country, 
and if utilized as a reagent for the preparation' of certain sprays less 
labor will be involved and costs will be reduced. Investigations pertain¬ 
ing to the relation of surface tension of numerous substances to the 
spreading qualities of these materials disclosed the fact that milk, 
either the whole or the skimmed product, has a very low surface tension. 
This low surface tension of milk, even when very dilute, suggested its use 
in the preparation of substitutes for the sulfur sprays. Laboratory 
experiments confirmed the belief that the spray materials described 
below may be prepared with the aid of milk and substituted advantageous¬ 
ly for those now in common use. It is the purpose of this paper, there¬ 
fore, to report briefly the results of the laboratory observations. 
Milk as a Wetting Agent For Lime And Sulfur. It is generally 
conceded that the various sulfur sprays used as summer fungicides are 
troublesome to prepare and disagreeable to apply. If lime sulfur is not 
used the more expensive commercial preparation must be obtained. 
If the spray is to be applied to tender foliage such as the peach tree, the 
self-boiled lime-sulfur must be home prepared. Often times this product 
is unsatisfactory due to the low grade materials used or to faulty manipu¬ 
lation of the method whereby the reaction is permitted to continue to the 
point where poly sulfides of sulfur are formed. This form of sulfur sub¬ 
sequently may cause foliage bum. 
The element sulfur is the active fungicidal ingredient in this class of 
sprays. Since powdered sulfur cannot be brought into water suspension 
easily, chemical or physical reactions are necessary to facilitate mixing 
with water. The peculiar physico-chemical properties of milk makes it 
especially well adapted for wetting finely ground sulfur after which it 
