78 
Journal of Agricultural Research 
Vol. XXXI, No. 1 
When it was observed that solutions containing soluble proteins 
spread well on most surfaces, the study of this class of material was 
extended to include many other similar substances. Among these, 
albumin, pepsin, hot water extracts of dried blood and of sage, 
dried skim milk powder and hot water extracts of such hays as clover, 
vetch, alfalfa, and dried grasses, spread well on all surfaces tested, 
even at low concentrations. This further substantiates the opinion 
that the soluble protein present is the active spreading agent. It is 
probable also that the active elements in the “Irish moss” used 
successfully by both Issleib (5) and Stearns (9) were soluble protein 
substances. 
The use of spreaders for general orchard sprays has become more 
prevalent during the last few years. The development of the com¬ 
mercial casein-lime product has contributed mainly to this increase. 
Questions regarding the advisability of using spreaders, the kind to 
use, and the concentration that will give best results can be answered 
satisfactorily only when all conditions are taken into consideration. 
The cost is perhaps the most important point to consider. If the 
cost is low, spreaders may be used advantageously in most sprays, 
but if they are as high as present prices that prevail for the Com¬ 
mercial casein-lime it should be used only for those sprays that un¬ 
questionably are improved by it and when beneficial results are 
obvious. It does not seem justifiable under average conditions to 
pay as much for the spreader as for the spray material itself, where 
comparative results indicate only a slight advantage in control. 
Under abnormal conditions and in parts of the country where severe 
epidemics of disease or insects prevail, their general use may be 
justified. The use of spreaders also in the last two cover sprays for 
apples and pears may be advisable in order to obviate th^ necessity 
of wiping the fruit and to allow a more even color development. 
If the cost of a spreader is low enough to allow a satisfactory 
profit to the grower, then the more general use of spreaders is advis¬ 
able. 
Considering price, skim milk and skim-milk products have proved - 
to be excellent substitutes for the commercial casein-lime spreaders. 
Laboratory tests and limited field experiments indicate that when 
skim milk is used at the rate if 2 to 3 quarts to 100 gallons it spreads 
well over many surfaces such as apple, pear, prune, peach, cherry, 
and cabbage leaves, and apple and pear fruits. The dried product \ 
used in equivalent amounts, as at the rate of solids in skim milk or 
2.5 ounces to the quart, and the partially dried clabbered milk such 
as is used for stock feed, give equally good results. It is necessary 
to add, a few ounces of hydrated lime or slaked quicklime to each 
quart of sweet skim milk and larger amounts to the commercial 
stock foods in order to neutralize the acidity and to bring the pro¬ 
teins into colloidal solution. Unless the lime is added spreading 
will not result. Skim milk, the dried or condensed skim milk, and 
the clabbered product are brought into solution easily, and in this 
respect they are preferable to the commercial casein-lime that must 
be worked carefully to a paste before putting into the spray tank in 
order to get best results. 
