316 
JOURNAL OF ECONOMIC ENTOMOLOGY 
[Vol. 16 
Table II. Effect of Bordeaux Spray Upon Different Instars of Empoasca mali 
Stage 
1 
2 
3 
4 
5 
6 
Average number of days 
insects lived on sprayed 
leaves 
1.56 
1.7 
2.06 
2.5 
2.58 
4.55 
Control 
2 
2.16 
3.07 
3.2 
3.39 
5.81 
The susceptibility of Empoasca mali nymphs to Bordeaux spray sug¬ 
gested the possibility of its effectiveness against certain other leafhop- 
pers. Accordingly similar experiments were made with Empoa rosae, Ery- 
throneura comes and E. tricincta, the three species feeding upon apple, 
and cultivated and wild grapes, respectively. Leaves of these plants 
were sprayed with this compound and the nymphs confined in vials for 
observation. Checks were used in all cases. The results are sum¬ 
marized in Table III. Bordeaux was decidedly toxic to these species 
under cage conditions. When fed on sprayed leaves these nymphs be¬ 
haved in practically the same manner as those of Empoasca mali. The 
mortality was high, successful ecdysis rare, and none were reared to 
maturity. It was comparatively easy to rear them through all stages 
upon untreated leaves. 
Table III. Effect of Bordeaux Spray Upon Three Species of Leafhopper Nymphs 
Species 
Number of days lived on 
sprayed leaves 
Number 
of tests 
Control 
No. of 
controls 
Maxi¬ 
mum 
Mini¬ 
mum 
Average 
Maxi¬ 
mum 
Mini¬ 
mum 
Average 
E. ccmes . 
10 
1 
2.8 
47 
22 
1 
7.78 
23 
E. tricincta .. 
7 
1 
2.53 
47 
8 
1 
4.4 
10 
E. rosae . 
5 
1 
2.5 
23 
9 
1 
5.5 
10 
In view of the fact that Bordeaux mixture might possibly be toxic 
under these conditions and not effective in the field, the following ex¬ 
periment was tried out with Empoasca mali. A plot of potatoes was 
sprayed three times, June 8, July 3 to 5, and July 27. Records were 
taken of the leafhopper infestations on sprayed and unsprayed plants 
Table (IV). Weather permitting, daily counts were made of the total 
nymph population on individual plants selected at random from the 
treated and check rows. The average daily count for one check plant 
was 50 while the sprayed vines averaged from 12 to 22. Such a differ¬ 
ence as this cannot be explained entirely as the result of a repellant 
action of Bordeaux upon this species, because frequent rains occurred 
directly after spraying and washed off a certain amount of the material. 
Moreover, plenty of unprotected leaves were exposed for oviposit ion 
owing to plant growth between spray applications, especially since the 
