262 JOUNRAL OF ECONOMIC ENTOMOLOGY [Vol. 17 
although not nearly so severe, by a closely related species, Nodonota 
puncticollis Say. 
Vice-President S. B. Fracker: The next paper is by S. W. Frost 
and E. M. Craighead. 
DUSTING FOR LEAF-HOPPERS (EMPOA ROSAE L.) 
IN BEARING APPLE ORCHARDS 
By S. W. Frost, and E. M. Craighead 
Abstract 
This paper open a new field in entomology, that of controlling leaf-hoppers 
(Empoa rosae L.). in bearing orchards. The seriousness of the pest and a new type of 
the injury is described. Field tests show that the nymphs and adults can readily be 
killed by nicotine dusts. 
The leaf-hoppers (Empoa rosae L.) have become a serious pest on 
bearing apple trees throughout Pennsylvania. During the past five 
years they have increased gradually in numbers and now, without 
doubt, can be classed among the most serious insect pests of the apple. 
During the summer of 1923 they were exceedingly abundant in well- 
cared-for orchards where no nicotine dust or spray was used during the 
summer. Their abundance demanded some immediate attention. 
Heretofore the necessity for special applications of spray or dust to 
control leaf-hoppers on bearing apple trees, has not appeared to be 
very urgent during normal seasons. Due to the fact that little or 
no data have been secured upon the practical value of spraying or 
dusting in bearing orchards, the writers have deemed it expedient to 
try some dusting experiments. This really opens a new held in economic 
entomology. 
Nature of the Injury 
The most serious injury is, no doubt, inflicted upon the foliage, 
although serious damage is sometimes done to the fruit. The leaf- 
hoppers suck the sap from the leaves, removing the chlorophyll and 
causing them to turn white in color. The leaf-hoppers suck out the 
contents of whole cells while the red-spiders puncture individual cells, 
removing only part of their contents. This accounts for the difference 
in appearance of two similar kinds of injury. Leaf-hopper injury, 
together with red-spider and scab injury often render the foliage almost 
functionless. Premature dropping of the foliage and the fruit takes 
place as the result of such injuries. No doubt a material reduction in the 
size of the fruit results in case of serious injury of this kind. No data, 
how r ever, have been secured to indicate this. 
