14 Farmers’ Bulletin 1225. 
Kerosene emulsion acted in the same way as nicotine and soap, 
killing the leafhoppers it hit, but having no lasting effect. Moreover, 
“hopperburn” appeared to be worse on these plants than on plants 
sprayed with any other material. 
WHAT BORDEAUX WILL DO. 
Bordeaux mixture properly applied to plants will drive away leaf- 
hoppers and keep the plants quite free of them as long as a good 
coating of spray is kept on the foliage. 
Bordeaux will also very largely prevent the symptoms of “ hopper- 
burn” from developing and will check the spread of what has already 
Fic. 12.—Potatoes not protected from “hopperburn” give poor yields. Five varieties shown here were 
never sprayed. ‘‘Hopperburn” killed all but late varieties, and even they were badly affected with 
‘hopperburn”’ on August 23. Compare with figure 11. 
appeared, (Fig. 11.) Unsprayed plants growing next to properly 
sprayed plants or even among them will be heavily attacked by 
“hoppers” and become badly affected with ‘“hopperburn.”” (Fig. 12.) 
The effect of Bordeaux on ‘‘hopperburn” varies with different 
varieties. Rural New Yorker plants well sprayed have remained 
almost free of any ‘‘hopperburn” until digging time. Triumph 
plants, on the other hand, while prevented from becoming badly 
diseased until after tubers had well developed, were affected much 
more by ‘‘hopperburn”’ than any other variety tested. Unsprayed 
Triumph plants died from the effects of ‘“hopperburn”’ before the 
middle of the season. 
