396 
JOURNAL OF ECONOMIC ENTOMOLOGY 
[Vol. 13 
Table II.— The Effect of Arsenical and Other Dusts on Larvae of Various Sizes (5-9 mm.) 
When the Larvae Are Placed on Tender Growing Peach Tree Twigs which Are 
Thoroughly Dusted with the Mixtures 
Experiment 
number 
Dusts 
Larvae alive 
inside of 
twig 
Larval injury 
but no larvae 
seen 
Larvae dead 
Larvae alive 
outside of 
twig 
No larvae or 
injury seen 
Total larvae 
in trials 
21 
Lead arsenate 
6 
0 
0 
1 
2 
9 
22 
Lead arsenate, 1 pt.-lime 5 pts. 
11 
3 
0 
0 
0 
14 
23 
Lead arsenate, 1 pt.-sulfur 1 pt. 
10 
2 
1 
1 
3 
17 
24 
Calcium arsenate 
6 
0 
2 
6 
2 
10 
25 
Calcium arsenate, 1 pt.-lime 5 pts. 
10 
0 
0 
0 
5 
15 
26 
Magnesium arsenate 
3 
0 
1 
4 
3 
11 
27 
Magnesium arsenate, 1 pt.-lime 5 
pts. 
4 
1 
1 
2 
10 
18 
28 
Zinc arsenite, 1 pt.-lime 5 pts. 
8 
2 
0 
1 
4 
15 
29 
Paris green 
0 
1 
3 
1 
1 
6 
30 
Paris green, 1 pt.-lime 5 pts. 
2 
2 
1 
0 
3 
8 
31 
Hellebore 
6 
2 
0 
1 
5 
14 
32 
Hellebore, 1 pt.-lime 5 pts. 
5 
0 
0 
1 
0 
6 
33 
Pyrethrum 
4 
0 
0 
5 
10 
19 
34 
Pyrethrum, 1 pt.-lime 5 pts. 
4 
0 
0 
1 
4 
9 
35 
Tobacco 
10 
0 
0 
0 
4 
14 
36 
Tobacco, 1 pt.-lime 5 pts. 
2 
1 
0 
0 
8 
*11 
37 
Lime (hydrated) 
6 
0 
0 
0 
0 
6 
38 
Lime-sulfur 
4 
1 
0 
0 
1 
6 
39 
Check 
12 
0 
0 
1 
1 
14 
form at the rate of 4 pounds to 50 gallons of water, but when the 
arsenicals were used at the rate of 2 pounds to 50 gallons of water, 
except Paris green, none of the larvae were killed. When the arsenicals 
were applied as dusts the calcium and magnesium arsenates, alone or 
in combination with hydrated lime, killed approximately the same per¬ 
centage of larvae as the lead arsenate (alone or in combination with 
lime). Dusts of hellebore, pyrethrum and tobacco did not keep the 
larvae out of thoroughly coated fruit. Pyrethrum seemed to have a 
slight repellent effect. 
Comparing the various series of experiments where twigs were used 
with those where peaches were used, the best killing results were ob¬ 
tained in the fruit series. This may be due to the fact that it is exceed¬ 
ingly difficult to get a thorough coating of poison (liquid or du&t) on 
and into all parts of a growing peach twig. The surface of the leaves 
and stem on a peach twig is smooth and this makes it difficult for the 
