198 Report OF THE BOTANICAL DEPARTMENT OF THE 
drew the conclusion: “ That bordeaux mixture prevents the solu- 
bility of the arsenites and their injury to foliage by virtue of its 
lime.” Weed* at the Ohio Station had previously (in 1889) 
pointed out the desirability of combining insecticides with fungi- 
cides. 
In recent years it has been very generally advised that paris 
green and other arsenical insecticides be not used alone but 
always in combination with milk of lime or with bordeaux mix- 
ture. Most fruit growers have now adopted this method, but 
many potato growers still persist in using paris green alone. 
The potato is less liable to arsenical injury than most other 
‘plants which require spraying; but it is an indisputable fact that 
the use of paris green on potatoes, as practiced by farmers, often 
results in serious injury to the foliage. Many cases of supposed 
blight are nothing: but paris green injury. Jones of the Vermont 
Station was first to direct attention to this and give a detailed 
description of the svmptoms of arsenical poisoning. He says:® 
“The poisoning or ‘burning’ of potato leaves by improper appli- 
cations of paris green is of more general occurrence than is com- 
monly supposed and the resulting injuries are frequently attrib- 
uted to the ‘early blight’ fungus. In cases of extremely strong 
applications of the paris green the leaves may be entirely killed 
or large areas ‘burned’ within a short time. Usually, however, 
its action is slower and longer continued. Its effects are then 
apparent as dead spots, black or brown in color, centering about 
flea-beetle punctures or other mutilations of the leaf. .* * * 
These spots slowly continue to enlarge for some time and as a 
result of the slow death and drying of the tissues the surface of 
each spot is thrown into concentric elevations or ridges forming 
distinctly ‘ringed spots. * * * These spots so closely resem- 
ble those caused by the ‘early blight’ fungus that they are ex- 
tremely deceptive.” Continuing, he points out the symptoms by 
which early blight and arsenical poisoning may be distinguished. 
It should be noted that Jones attributes the injury to improper 
applications of paris green. . 
*Weed, C. M. On the Combination of Insecticides and Fungicides. Agri- 
cultural Science, 3:263. Oct., 1889. See also Ohio Exp. Sta. Bul., Vol. I, 
No. 7, p. 186. Nov., 1889 j 
*Jones, L. R. Potato Blights and Fungicides. Vt. Exp. Sta. Bul. 49:97. 
Dec., 1895. 
