22 SEVENTEENTH Report STATE ENTOMOLOGIST OF MINNESOTA—1918 
2. Cultivate and perform all necessary operations throughout 
the season, with the exception of spraying. 
3. Allow authorized representatives of the Experiment Station 
to come onto his property at any time for making ob- 
servations, spraying or collecting. 
4. Furnish a team for use in spraying, whenever it was deemed 
necessary by the man in charge of the experiments. 
5. Furnish water and a place for mixing materials. 
6. Furnish a dry storage place for the insecticides. 
7. Keep the man in charge of the experiment informed as to the 
dates when digging was contemplated, so that he might 
be present to record the yield. 
The Experiment Station agreed to: 
1. Furnish a suitable machine for the work and keep it in repair. 
2. Furnish all insecticides and other spray materials. 
3. Mix and apply the materials when necessary. 
4. Use no materials on a large scale except such as had been 
given preliminary tests and had shown promise of suc- 
cess. 
5. Keep all records and be responsible for all observations. 
This agreement fixed the responsibility and made clear to each 
party his duties in connection with the experiment. 
Under the old system of co-operation, it was impossible to run a 
series of experiments on the same farm, using a variety of insecticides 
side by side, since the farmer very naturally was unwilling to spend 
the extra time and trouble in spraying that such a set would necessi- 
tate. Since it is impossible to accurately compare results when plots 
are on different farms or even more difficult when they are located in 
different counties, the confining of all the potato spraying experiments 
to one farm was exceedingly advantageous. 
Potato INSEcTs OCCURRING ON THE PLOTS 
The plots selected for the work were well supplied with insect 
pests, altho no disastrous outbreak of any species was threatened. 
The adult colorado potato beetle, Leptinotarsa decemlineata Say, was 
very abundant in the spring. The potato flea beetles, Epetrix cucu- 
meris Harr., and the leaf-hoppers, Empoasca mali Le Baron, were the 
other primary pests. In addition to these insects which were of 
primary importance, the tarnished plant bug, Lygus pratensis Linn., 
and several other bugs were common. 
