PRELIMINARY NOTES ON POTATO LEAF-HOPPER Il 
so rapidly, however, and were killed by freezing weather before ma- 
turity. The adults of this generation fed on potato until. the plants 
were killed by frost and then migrated to other food plants, where 
they fed until hibernation. 
Control 
Experiments were conducted during 1922 to determine the value 
of spraying and dusting with various compounds for the control of 
this insect. Tenth-acre and one-acre plots of Bliss Triumph and Green 
Mountain potatoes were used in order to test the same materials on 
an early-maturing and a late-maturing variety. These fields were 
planted in duplicate, each set receiving applications of the following 
materials : 
Liquid bordeaux mixture 
Liquid bordeaux mixture and Black Leaf 40 
Black Leaf 40 alone 
Dosch copper calcium arsenate dust 
Dosch copper calcium arsenate and nicotme dust 
Nicotine dust alone 
When no arsenical was in the mixture an application with an 
arsenical was made when needed to take care of the Colorado potato 
beetle. All sprays were applied with a Friend power sprayer using 
a four-row, 3-nozzle-per-row boom, and dusting was done with a 
Niagara power duster. 
Times of spraying.—All plots received four applications of liquid 
or dust material at intervals of about two weeks. The tenth-acre plots 
were first sprayed and dusted on June 24, when the potato plants were 
about six inches high. Subsequent applications were made on July 7, 
July 25, and August to. The Bliss Triumph plants were mature at 
the time of this last spray and died soon after; the Green Mountain 
plants remained green until frost. The acre plots were sprayed on 
June 29, July 14, July 27, and August 18, and remained green until 
the first of September. The tables show the results of these tests. 
During the course of these spraying experiments accurate counts 
were made in the various plots of the percentage of foliage injury, 
and the average number of hoppers per plant. The results gave some 
idea of the relation of the hoppers to the percentage of injury and of 
the efficiency of the spray materials used. | 
On the early maturing variety, leaf-hoppers occurred in greater 
abundance over a shorter period of time. The percentage of injury 
during their maximum feeding period was approximately the same 
on both varieties. 
