32 FIRST AN"NUAL REPORT OF THE STATE ENTOMOLOGIST. 



There is no foutidatioti for the fear entertained by some persons 

 that potatoes grown from plants treated with the poison are either poi- 

 sonous or unwholesome. Repeated examinations of such potatoes made 

 by our best chemists have failed to give the least trace of arsenic; and 

 if tlie potatoes prove watery or appear to be in otherwise bad condi- 

 tion, it may be the result of a diminished foliage of the plants 

 through the insect attack, rather than the poison administered. 



Nor can we believe, in view of recorded experiments, that the poi- 

 son, as it is now being employed, can affect the soil so as to interfere 

 with healthful plant-growth. Prof. R. 0. Kedzie, of the Michigan 

 State Agricultural College, has shown conclusively that the arsenic 

 of Paris green does not remain in the soil as such for four mouths, 

 but before that time it undergoes chemical changes which render it 

 harmless.* 



Mr. Wm. McMurtrie, as chemist of the U. S. Department of Agri- 

 culture, has instituted a series of very interesting and satisfactory ex- 

 periments to test the influence of Paris green upon soil and the plants 

 grown therein, which have beenpublishedjn detail, accompanied with 

 copies of the photographs of the fifteen pots of pease experimented 

 upon and treated respectively with from one hundred milligrams to 

 one grain of the Paris green, f The results obtained were these : 



1. An aggregate of 906.4 pounds of Paris green per acre must be 

 applied to the soil before any injurious effects on plant-growth are 

 appreciable [the ordinary application to a potato field is from a pound 

 to two pounds per acre.] 



2. Arsenic cannot be absorbed and assimilated by the plant in the 

 economy of growth. All of the plants grown in the arsenical soil, 

 tried by Marsh's test, failed to indicate the presence of arsenic. 



3. Potatoes subjected to applications of Paris green failed to give 

 evidence of the presence of arsenic. 



The Insects that may be destroyed by Paris Green. — In 

 addition to the Colorado beetle, there are many other injurious species 

 against which this poison maybe conveniently used. It would be well, 

 however, not to resort to its aid except in cases where it will accomplish 

 the desired purpose better (convenience, economy and efficiency being 

 considered) than non-poisonous substances. 



It may be advantageously used against several other of the potato- 

 insects which occasionally appear in numbers and destructiveness almost 

 equaling the Colorado beetle, as, for example, the three-lined leaf- 

 beetle — Lema trilineata (Oliv.), the ash-gray blister-beetle — Macroha- 



*Quoted in the Eighth Annual Report on the Insects of Missouri, 1876, p. 7. 



i Report of the Commissioner 0/ Agrioultiire tor tho year 1875, pp. 144-147, pi. 10. 



