July 1,1925 Spreaders and Spreading Qualities of Spray Materials 79 
THE EFFECT OF SPREADERS ON THE AMOUNT OF POISON THAT ADHERES 
When a good spreader is used the whole surface is wetted and an 
even coating of the spray is obtained. As the film is formed the 
excess runs off and gives the appearance of excessive drip. In order 
to learn whether less poison adheres to the surface when a spreader 
is used, a series of laboratory tests were made. Apple and pear 
leaves wei*e sprayed with lead arsenate at several dilutions with and 
without a spreader in the spray. Milk, commercial casein-lime, and 
laboratory preparations of casein and hydrated lime were used as 
spreaders. The leaves were sprayed with an atomizer and sus¬ 
pended at a 45° angle to dry and to allow the excess to drain off. 
The surface areas of the leaves were measured by means of a pla- 
nimeter. The amount of arsenic that adhered to 100 square inches 
of leaf surface was then determined. The results obtained are 
given in Table IV. 
Table IV .—The amount of lead arsenate on 100 square inches of leaf surface 
Lead arsenate 
concentration 
Spreader treatment 
Apple 
Pear 
2 to 100_ 
None_ 
Mgm. 
7.2 
Mgm. 
4.9 
2 to 100_ 
Casein 0.05 per cent in saturated Ca(OH)a solution_ 
6.8 
6.2 
2 to 100_ 
Casein 0.05 per cent+Ca(OH )2 0.08 per cent_ 
6.1 
5.6 
4 to 100.. 
None___ 
12.0 
16.0 
4 to 100_ 
Casein 0.10 per cent in saturated Ca(OH )2 solution__ 
9.3 
5.5 
4 to 100. 
Casein 0.05 per cent+Ca(OH )2 0.08 per cent_ 
10.0 
8.5 
4 to 100_ 
Skim millr 1.4 per cent+Ca(OH )2 0.1 per cent_ 
13.1 
7.2 
4 to 100_ 
Whole milk 1.4 per cent+Ca(OH )2 0.05 per cent__ 
12.0 
11.0 
4 to 100. 
None_ r - - - 
11.8 
16.4 
4 to 100.. _ 
C as Ain ft 01 per eent-f-CafOTT^ ft.ft2 per a Ant 
8.8 
11.3 
4 to 100. 
Casein 0.02 per cent+Ca(OH )2 0.04 per cent___ 
15.5 
10.4 
4 to 100.... 
Casein 0.05 per cent-j-Ca(OHl? ft. 1 per cp.nt _ _ 
8.3 
11.4 
4 to 100. 
Commercial casein-lime 0.15 per cent_ 
11.1 
11.9 
6 to 100_ 
None _ . _ _ _ . ...... 
19.0 
23.5 
6 to 100. 
Casein 1 per cent in saturated Ca(OH )2 solution_ 
10.2 - 
13.3 
6 to 100_ 
Casein 0.02+Ca(OH)2 0.04 per cent___ 
21.2 
12.6 
6 to 100__. 
Skim milk 2.0 per cent+Ca(OH )2 0.04 per cent____ 
19.5 
12.4 
6 to 100_ 
Skim milk 2.0 per cent+Ca(OH )2 0.08 per cent... 
17.0 
11.0 
It will be noted from the results given in Table IV that there is an 
appreciable variation which, perhaps, may be due to the age and 
size of leaves used and to the amount of lead arsenate that drained 
to the lower tip of the leaf. In general, however, it may be said 
that at all dilutions the apple leaves sprayed without a spreader 
show no more arsenic than where a spreader had been used. With 
the pear leaves, larger amounts of lead arsenate were found on the 
leaves sprayed without a spreader, except at the 2 :100 dilution. 
However, the leaves sprayed without a spreader were covered in 
spots only, while where a spreader was used the coating of poison 
was an even film. 
The amount of lead arsenate that adhered to the leaves was, for 
the most part, proportional to the concentration used. Approxi¬ 
mately the same amount of lead arsenate was found on leaves where 
milk had been used in the spray as with the various forms of casein- 
lime. 
In addition to the laboratory tests, samples of leaves sprayed 
under normal conditions in the orchard were collected and the amount 
of lead arsenate that adhered was determined. Several different 
