54 
PAPEES ON INSECTS AFFECTING VEGETABLES. 
On the day following the second application of the sprays a count 
of the infested plants in each plat was made and the following figures 
obtained: 
Table II. — Results of spray applications against the Colorado potato beetle, Norfoll:, 
Va., May, 1911. 
Plat 
No. 
Insecticide used. 
Number 
of in- 
fested 
plants. 
Number 
of un in- 
fested 
plants. 
• 
Infesta- 
tion. 
I 
II 
Lime-sulphur (2-50 formula) and 3 pounds of arsenate of lead 
Arsenate of lead, 3 pounds to 50 gallons of water 
37 
118 
216 
206 
152 
225 
347 
622 
169 
1,048 
741 
555 
Per cent. 
9.6 
15.9 
III 
Lead ehromate, 2 ounces to 4 gallons of water, and 1 ounce to 1 gal- 
+56. 
IV 
Arsenite of zinc, 1 J pounds to 50 gallons of water 
16.4 
V 
VI 
Bordeaux mixture (4-6-50 formula) and 1§ pounds Paris green 
Bordeaux mixture (4-0-50 formula) and 1 J pounds arsenite of zinc. . . 
+ 17.0 
28.8 
It will be seen that the results obtained from the use of lead 
ehromate were very unsatisfactory as compared with those in the 
case of other insecticides used. The lead ehromate employed was in 
the form of a powder, and great difficulty was experienced in making 
it mix well with water, it having a tendency to settle quite rapidly, 
requiring constant agitation to keep it in solution. It adhered well 
to the foliage, and its color stood out quite prominently in contrast 
to the other plats. However, the young larvae seemed to be able to 
feed on plants that were thoroughly covered with the material without 
receiving much injury. 
The arsenite of zinc employed was also in the powdered form. It is 
much lighter than lead ehromate and remains in suspension in water 
much better. It adheres to the foliage very well and does not, so far 
as could be observed, burn or injure the plants in any way. 
The percentage of infested plants in the plat that was treated 
with Bordeaux mixture and arsenite of zinc was somewhat greater 
than in the plat in which the arsenite of zinc alone had been used. 
This was no doubt due partly to the fact that the Bordeaux-arsenite 
of zinc plat was in a different field, one which had been in potatoes the 
previous year and was thus subject to the attack of a greater number 
of beetles. Also, many of the plants which were counted as infested 
were only slightly injured, and it is doubtful if the yield of potatoes 
would have been much lessened. 
On June 29 the potatoes were dug, and following are the weights 
of one row of potatoes in each of the first four plats. 
