14 BULLETIN 535, U. S. PEPARTMENT OF AGRICULTURE. 



deaux mixture has been applied, the flea-beetles of different groups 

 are nearly always repelled. It is evident that arsenicals repel, but 

 in the case of flea-beetles Bordeaux mixture is more effective, a fact 

 which has been known for many years. 



During the season of 1914, when injuries by the horse-radish flea- 

 beetle in Wisconsin were very serious and the root crop was much 

 reduced, it was found necessary to bring roots from farther south 

 to supply the usual trade. At this time arsenate-of-lead paste, 6-J 

 pounds to 50 gallons of water, was used four times with considerable 

 success. In the spring of 1915 the field was plowed, the roots col- 

 lected, stripped of every vestige of leaves, and planted about a quar- 

 ter of a mile from the old bed. This reduced the beetles to such an 

 extent that very little injury was apparent until the middle of June, 

 1915. 



On June 23 the plants were sprayed with arsenate of lead, and the 

 numbers were reduced considerably. About three weeks later the 

 poison was applied again. In the latitudes of Wisconsin, Michigan, 

 Ohio, Pennsylvania, Delaware, New York, Indiana, and Iowa the 

 spray should be administered at intervals from about the last week 

 in April until late in July. 



VALUE OF CULTURAL PRACTICES. 



The importance of the employment of methods for the control 

 of these insects as pests is exemplified by the experience of a firm at 

 Green Bay," Wis. Before the advent of flea-beetles, truckers were able 

 to raise horse-radish on a large scale from the same beds for several 

 years at a time, but now the abundance and destructiveness of this 

 flea-beetle makes it necessary to change these cultural practices com- 

 pletely in order to produce a crop, and it is necessary to replant a 

 new bed from old roots every season. 



SUMMARY. 



The growing of horse-radish in the North is menaced by the intro- 

 duction from Europe of a small insect known as the horse-radish flea- 

 beetle. The beetle is oval in outline, about one-eighth of an inch 

 long, with yellow elytra or wing-covers bordered with black, and 

 with a longitudinal black band through the middle. The larvae or 

 young bore into the petioles or midribs of horse-radish, and the 

 adults feed on the leaves and gouge deeply into the midribs, causing 

 drying and death. 



The beetle was first recognized in this country at Chicago, 111., in 

 L893, since which time its area of distribution has increased until it 

 now occurs from New York and New Jersey to Quebec, Canada, and 

 westward to Nebraska. 



