Diseases of the Potato. 323 



mucli greater difficulty with water. In our experiments it proved 

 effective when used at the rate of one ounce to four gallons of 

 water. 



Within the past few years another form of arsenic, known as 

 English purple poison,"^ has been offered for sale in this country. 

 The results of various trials of the poison upon potato foliage show 

 that when used at the rate of one ounce to four gallons of water it 

 is effectual in destroying the insects. But it also possesses the 

 serious objection of mixing slowly with water. 



2. Flea-beetles — The most serious insect enemy of potatoes is 

 undoubtedly the flea-beetle. The insects are scarcely a tenth of an 

 inch in length ; they are nearly black in color, and the quickness of 

 their movements has caused them to receive their popular name. 

 There appear to be several broods each season, so their work is 

 more or less continuous during the growing season. 



Many remedies have been suggested for the destruction of this 

 pest. Among them may be included the following : Paris green ; 

 London purple; decoction of tobacco; kerosene emulsion; air- 

 slaked lime; land plaster; wood ashes; tobacco powder; Bordeaux 

 mixture. 



With the exception of the last named remedy, all the above 

 appear to be without practical value for potatoes. 1 have tried 

 Paris green, London purple, kerosene emulsion, tobacco powder 

 and air slaked lime with no apparent beneiit ; and as others have 

 failed in obtaining satisfactory results with these as well as with 

 all the others except the Bordeaux mixture, their use cannot be 

 recommended. 



The Bordeaux mixture, however, appears to be a promising 

 remedy. Jones has tested the material very thoroughly and the 

 following is his opinion of the value of his treatments. f '' The 

 actual number of holes per leaflet, from the unsprayed row was 

 found upon counting to be 262, which from the sprayed row the 

 average was but 12. * * * These results bear out completely 

 the conclusions of last year, and justify the claims that the Bordeaux 

 mixture is the best practical remedy known for the flea-beetle as 

 it occurs upon potatoes." The leaves examined by Professor Jones 



*The poison was introduced by Henry S. Ziegler, 400 N. Third street, Phila- 

 delphia, Pa. It contains 36.75 per cent arsenic trioxide, 14.58 per cent of which 

 is soluble in water. 



i Ann. Rep. Vt. Agric. Exp. Sta. 1894, 96. 



