80 
Journal of Agricultural Research 
Vol. XXXI, No. 1 
commercial brands of lead arsenate were used. The leaves were 
collected a few hours after spraying and the surface area measured 
as before. Table V gives the results obtained. 
Table V .—The amount of lead arsenate on 100 square inches of leaf surface sprayed 
in the orchard 
Lead arsenate 
i 
Concentration 
Spreader used 
Mgm. 
per 100 
square 
inches 
No. 1_ 
2 to 100_ 
None_ _ _ 
26.4 
31.6 
36.2 
25.2 
24.3 
29.3 
45.2 
55.5 
Do_ 
2 to 100_ _ 
Casein 0.05 per cent__ _ __ 
Do _ 
2 to 100._ . _ _ 
Skim milk 0.60 per cent 
Do_ - 
2 to 100_ 
Casein 0.05 per cent_ _ 
No. 2_ 
2 to 100_ 
None_ _J_ 
Do_ 
2 to 100_ 
Casein 0.05 per cent__ ______ 
No. 3 . 
4 to 100 _ 
None_ _ _ 
Do 
4 to 100_ _ 
Casein 0.05 per cent__ _ _ 
From the results in Table V it will be noted that much more lead 
arsenate adhered to the leaves sprayed under orchard conditions 
than when sprayed in the laboratory. This may be due to the 
carbon dioxide of the breath used to force the spray on the leaves 
and to the force used in applying the spray. The amount of lead 
arsenate that adhered was generally higher on the leaves where 
a spreader had been used than where lead arsenate only had been 
applied. Skim milk, apparently, was as good as the casein-lime 
spreaders. It spread well and formed a good even coating of the 
poison on the leaf surface. 
Both the laboratory and orchard experiments indicate that skim 
milk or casein-lime spreader may be used advantageously if properly 
applied. The amount of spreader to use for best results is an im¬ 
portant phase of the work and must be decided by field observations. 
Many variable factors that exist at the time of application should 
be taken into consideration and the amount of spreader used should 
be controlled accordingly. The pressure or force used, the kind of 
surface to be covered, the type of gun or nozzle used, and the climatic 
conditions, may influence the amount of spreader that will give best 
results. Too much spreader may cause excessive drip if sprayed to 
the drenching point. On the other hand, drenching with good 
force with a minimum amount of spreader is advisable. Most of 
these points should be definitely settled by field observations. 
SUMMARY 
No definite proportional relationship could be established between 
the surface tension values of spreader solutions and the observed 
spreading properties of the different substances. However, a solu¬ 
tion having a low surface tension or a low interfacial tension to oil 
probably has spreading properties. 
Of the materials tried, water-soluble protein substances gave best 
spreading at lowest concentration for the greatest number of surfaces 
tested. Skim milk, neutralized with hydrated lime, and certain other 
milk products appear to be the best material for practical purposes. 
The concentration of a spreader solution that will give best results 
depends upon a number of variable factors, such as the type and 
age of the surface to be sprayed, the force used, and climatic 
conditions. 
