264 
JOURNAL OF ECONOMIC ENTOMOLOGY 
[Vol. 17 
they fell upon the lower leaves of the tree. Heavy white muslin sheets 
were placed under the trees to catch the hoppers as they fell. They 
were so numerous that it was difficult to make counts. A few counts 
% 
were made of the number of leaf-hoppers per square foot from which 
the number upon the sheet was estimated. They were so abundant 
that they could be measured by the pint. An average twelve year old 
tree with a medium infestation yielded about a half a pint of leaf- 
hoppers. Older trees yielded over a quart of leaf-hoppers 
Summary of Leaf Hopper Counts in Dusted Plats, Arendtsville, Pa., 1923 
BEFORE DUSTING 
No. leaves 
% 
No. 
No. leaf 
No. leaves free 
free 
leaf- 
hoppers 
Material 
examined from 
leaves 
hoppers 
per leaf 
L. hoppers 
2% Nic. Sulphate, H. Lime. . . . 
. . . . 430 
89 
20.6 
1219 
2.8 
l%% Free Nicotine Dolomite. . 
.... 567 
185 
30.8 
1035 
1.8 
2% Free Nicotine Dolomite. . . . 
.... 436 
115 
26.3 
998 
2.2 
2% Free Nicotine Dolomite. . . . 
.... 654 
198 
30.2 
913 
1,3 
2% Nic. Sulphate H. Lime. 
.... 656 
261 
38.8 
700 
1.0 
AFTER DUSTING 
2% Nic. Sulphate, H. Lime. . . . 
. . . . 498 
413 
82.8 
150 
.30 
1 Free Nicotine Dolomite . . 
. . . . 1266 
1232 
97,3 
34 
.02 
2% Free Nicotine Dolomite. . . . 
. . . 1227 
1175 
95.6 
65 
.05 
2% Free Nicotine Dolomite. . . . 
. . . 1485 
1210 
81.5 
406 
.26 
2% Nic. Sulphate H. Lime . . . . 
. . . . 1749 
1495 
85.4 
175 
.10 
Applications made on June 12th. 
Conclusion 
While we cannot say that dusting or spraying for leaf-hoppers in 
bearing orchards will be practical, because of the great abundance of 
these insects and the possibility of the orchard becoming reinfested from 
adjoining orchards, the great abundance of leaf-hoppers in Pennsylvania 
and their seriousness as a pest on apple, demands considerable attention. 
Nicotine dusts have given an excellent percentage of kill under favorable 
• 
■conditions. It still remains to be discovered whether one or two appli¬ 
cations of nicotine dust during June will be sufficient to keep the hoppers 
under control. The cost of nicotine dust or spray would prohibit a 
larger number of applications. 
Vice-President S. B. Fracker: We will now listen to a paper by 
H. A. Gossard. 
