24 SEVENTEENTH Report STATE ENTOMOLOGIST OF MINNESOTA—1918 
escaped observation. At this time the potato flea beetles were quite 
abundant and it was primarily for this insect that the bordeaux mix- 
ture was used. The water used in all the experiments was a natural 
soft water from lakes nearby. [Everything that went into the tank, 
including the water, was poured through a fine wire strainer. As a 
result of this care, combined with the fact that large chambered noz- 
zles were used, and that the machine was washed out after each day’s 
work, practically all nozzle trouble was eliminated. 
The weather at the time of spraying was dry and clear with a hot 
sun. There was a light breeze from the west and south. The weather 
continued dry for several weeks following spraying so that the poisons 
were not washed off the plants, thus giving opportunity for maximum 
efficiency of all the poisons used. Under these ideal conditions, the 
effects of the various poisons on the potato beetles were remarkably 
uniform. Before spraying, the adult beetles were abundant in all parts 
of the field, and plants on which eggs were found averaged seventeen 
to each row. One week after spraying the adult beetles were remark- 
ably few in number and less than three plants in each row showed 1n- 
jury from larvae. These rows were about sixty rods long. 
Thus it would appear that all four of the poisons tested in this 
experiment were equally effective under ideal conditions, so far as the 
potato beetle was concerned. The dilutions used were two pounds to 
the acre, or four pounds to each one hundred gallons of liquid, in the 
case of lead arsenate, calcium arsenate, and zinc arsenite, and one 
pound to the acre, or two pounds to one hundred gallons of liquid 
in the case of paris green. Each of these materials was applied both 
with and without 4-4-50 bordeaux mixture. All of these materials, 
including bordeaux mixture at the dilutions used, appeared ineffective 
as a poison or deterrent for the flea beetle adults. 
The second spray was applied July 1. At this time the vines had 
doubled in size, leaving a large unpotsoned surface on every plant. 
There were, however, so few potato beetles present that it is probable 
the average grower would have considered the field “bug free,” and 
would not have deemed spraying necessary at this time. There were 
enough beetles present, however, to form the nucleus of a consider- 
able infestation if permitted opportunity to increase unchecked. This 
possibility was illustrated by a field on another farm just across a 
railroad track from the experimental plots. This field was later quite 
badly injured by beetles altho it was comparatively free at the time 
the above observations were made. Materials were used at the same 
dilution for this as for the first spraying. The weather was warm and 
dry, making conditions again ideal for the maximum efficiency of the 
