June, ’23 
smith: vacuum fumigation 
317 
female leafhopper prefers the growing tip for this. These factors 
tended to offset partly the deterrent action of this material. Therefore, 
as the insects were left undisturbed after each observation was made, 
it is believed that these records represent a true insecticidal action of 
this compound to the nymphs. The apparent discrepancy between 
the length of life of certain of the plants after the counts were begun, 
and the relative daily nymph count, was due to the greater size and vigor 
of these, which was general throughout one side of the field. This was 
not the result of better protection afforded by any one type of Bordeaux 
mixture, as check rows located at regular intervals throughout the plot 
showed this to be due to more favorable conditions for plant growth at 
this part of the field. These larger plants not only lived longer but sup¬ 
ported a somewhat larger leafhopper population. 
Table IV. Summary of Field Counts on Plants Sprayed With Bordeaux Mixtures 
Treatment 
Number of 
plants 
Average No. of 
nymphs per 
plant 
Average life of 
plant after 
infestation 
Average daily 
No. of nymphs 
per plant 
4-4-50 
4 
848.7 
37.25 days 
22.7 
Glidden 
4 
493.5 
39.5 “ 
12.49 
Grasselli 
4 
746.75 
41.75 “ 
17.8 
Sherwin-Williams 
4 
894.75 
44.5 
20.0 
Control 
1 
1350 
27 
50 
The above tests indicate that Bordeaux mixture is a specific insecti¬ 
cide for at least one and possibly four species of leafhoppers, namely 
Empoasca mali, Empoa rosae, Erylhroneura comes and E. tricincta. 
They appear to substantiate the previous statement by the senior 
writer that Bordeaux not only protects potato vines from leafhoppe r 
attacks by its repellant action on the ovipositing females but that it also 
protects them because of its toxicity to the nymphs. It should therefore 
be classed as a specific insecticide for leafhoppers of certain types. 
VACUUM FUMIGATION EXPERIMENS WITH BROWN TAIL 
MOTH AND EUROPEAN CORN BORER LARVAE 
UNDER WINTER CONDITIONS 
By R. I. Smith, Boston, Mass. 
Abstract 
Fumigation of brown-tail moth, Euproctis chrysorrhoea nests, in mid-winter show 
that brown-tail moth larvae were killed when fumigated at 50° F., and in many 
cases when the temperatures were as low as 39° F. European corn borer larvae, 
Pyrasuta nubilalis , taken from a storeroom at a temperature of 40° to 45° F., and 
fumigated in a temperature of 65° to 70° F., were not killed. Borers frequently 
counted as dead from two to fourteen days after fumigation were found to recover 
