ARSENITE OF ZINC AGAINST POTATO BEETLE. 
55 
Table III. — Yields of potatoes from one row from each of Plats I, II, III, and IV, 
sprayed as indicated in Table I. 
One 
row 
from 
plat 
No. 
Insecticide used. 
Number 
of plants 
in row. 
Weight 
of No. 1 
potatoes. 1 
Weight 
of No. 2 
potatoes. 2 
I 
Lime-sulphur and arsenate of lead 
384 
368 
385 
374 
Pounds. 
188i 
172| 
128 
143| 
Pounds. 
25| 
II 
Arsenate of lead 
26 
III 
Lead chromate 
191 
IV 
18 
Excellent to good. 
2 Fair to indifferent. 
By taking the yield of the same number of plants from each row the 
contrast between the different rows will be more marked. Table IV 
represents the yield of 374 plants from each row: 
Table IV. — Yields of potatoes from 374 plants from one row from each of Plats I, II, 
III, and IV, sprayed as indicated in Table I. 
One 
row 
from 
plat 
No. 
I 
II 
III 
IV 
Insecticide used. 
Lime-sulphur and arsenate of lead 
Arsenate of lead 
Lead chromate 
Arsenite of zinc 
Number 
Weight 
of plants 
of No. 1 
m row. 
potatoes. 1 
Pounds. 
374 
183.26 
374 
175. 401 
374 
124. 168 
374 
143.5 
Weight 
of No. 2 
potatoes. 2 
Pounds. 
25.05 
26.18 
19.07 
18 
1 Excellent to good. 
2 Fair to indifferent. 
SPRAYING EXPERIMENTS WITH ARSENITE OF ZINC AT VARIOUS 
STRENGTHS. 
An experiment with the three following strengths of arsenite of 
zinc in controlling the Colorado potato beetle was begun at the Vir- 
ginia Truck Experiment Station, Norfolk, Va., on May 31, 1911. 
No. I, arsenite of zinc, 1 pound to 50 gallons of water. 
No. II, arsenite of zinc, 1J pounds to 50 gallons of water. 
No. Ill, arsenite of zinc, 2 pounds to 50 gallons of water. 
On the day the spraying was done (May 31) the rows sprayed with 
No. I, No. II, and No. Ill had 47, 86, and 88 infested plants, respec- 
tively. 
On June 2 the row treated with No. I had 33 infested plants, a 
decreased infestation of 14 plants, or 29.8 per cent. The row treated 
with No. II had 57 infested plants, a decreased infestation of 29 
plants, or 33.7 per cent, while the row treated with No. Ill had 38 
infested plants, a decreased infestation of 50 plants, or 56.8 per cent. 
