BULLETIN 535, U. S. DEPARTMENT OF AGRICULTURE. 



Koch. 1 It was obtained for the first time in 1893 on the withered 

 leaves of horse-radish in a vacant lot within a fourth of a mile of the 

 grounds of the Columbian Exposition at Chicago, 111. It is possible 

 that the species was actually introduced at about that time, but 

 probably the time Avas one, two, or more years earlier, and it was not 

 reported as a pest until 1908. 



The larva> as well as beetles live on the leaves and petioles of 

 the common horse-radish ( '[Nasturtium] Radicula armoracia) and 

 when numerous injure the plant to such an extent as to reduce 

 materially the root crop. The larva? mine the petioles or midribs 

 (fig. 2), while the adults feed on the leaves, causing the charac- 

 teristic flea-beetle injury — withering and dying — or gouge deep pits 

 in the petioles or midribs. 



This beetle belongs to the same genus 

 as the Avell-known injurious striped 

 cabbage flea-beetle {Phyllotreta vittata 

 Fab.) but may be distinguished readily 

 from all other species occurring in 

 this country by its elytra or wing- 

 covers, which are mostly of a pale 

 cream color with a comparatively nar- 

 row sutural black stripe, as shown in 

 figure 1. 



The horse-radish flea-beetle, having 

 recently become an economic factor 

 in the growing of horse-radish 2 on a 

 commercial scale in Brown County, 

 near Green Bay, Wis., the junior 

 author has been able to trace its life 

 economy and history. It first appeared 

 in sufficient numbers to be seriously in- 

 jurious in the summer of 1914, when it 

 was reported and observed by Prof. J. G. Sanders. In the two years 

 following, the beetles reappeared in large numbers in the same 

 locality. 



While as yet not very generally distributed and confined to 

 attacks on the relatively unimportant crop of horse-radish, the pos- 

 sibility that this insect in its new domain may adapt itself to the 

 other and more important members of the cultivated cruciferous 

 plants renders it worthy of such notice as can be supplied. 



1 Order Coleoptera, family Chrysomelidae, subfamily Ilaltlcini. 



8 The authors desire i" acknowledge the cooperation of the Departmenl of Economic 

 Entomology, University of Wisconsin, and the many favors received from Mr. George B. 

 Smith, Green Bay, Wis., on whose farm the junior author was stationed when many of 

 the data In this papei were obtained. 



Fig. 1. — The horse-radish flea- 

 beetle (.Phyllotreta armoraciae) : 

 Adult. Greatly enlarged. (Origi- 

 nal.) 



