330 MAINE AGRICULTURAL EXPERIMENT STATION. I907. 



red lead, but the largely increased numbers on nearby, unsprayed 

 plants showed, that they had migrated to these. The length 

 of time that a spraying with red lead would protect the foliage 

 did not appear to exceed that of Paris green. The only con- 

 clusion that could be drawn from the field trials was that while 

 red lead used in sufficient quantities will keep the larvae away 

 from potato foliage there is nothing to recommend it as a sub- 

 stitute for Paris green as an insecticide. 



In order to determine just what the action of red lead is 

 upon the young larvae the Station Entomologist tested the matter 

 in the insect house. The results of her experiments and her 

 conclusions are as follows : 



"Twelve insectary tests were made to determine the value of 

 dry red lead as an insecticide, about 50 potato beetle larvae 

 being involved in each test. It was found that leaves heavily 

 coated with red lead were to a very considerable extent avoided 

 by even the large larvae and this substance has some value as 

 a repellent. Some of the very young larvae that trailed through 

 the red lead which adhered to them died, and this powder served 

 to a slight degree, therefore, as a contact insecticide. Without 

 going into the details of any of the tests it is perhaps sufficient 

 to state that of the 2 lots of larvae caged July 27 at 4 P. M. 

 upon potato plants, one of which was treated with red lead and 

 one with Paris green in exactly similar ways, an examination 

 July 28 at 9 A. M. showed 50 live and apparently healthy larvae 

 in the red lead cage and 43 dead and 7 alive (part of which 

 subsequently died) in the Paris green cage." 



