THE HOP FLEA-BEETLE. 87 



that imskilled laborers are likely to make imperfect emulsions and 

 waste the material in applj'ing it. With competent help, and other 

 things being equal, kerosene-soap emulsion should be the more eco- 

 nomical spray. It Avould beM'ell to continue the use of kerosene emul- 

 sion at varying rates, including the rate that has been already used 

 and up to 1 pound of soap and 1 gallon of kerosene emulsion to 30 

 gallons of water. It is possible that if the emulsion were diluted 

 with 10 gallons of water still better results might be obtained, but if 

 labor is cheap the weaker solution, other things being equal, should 

 prove to be the more economical preparation. 



BORDEAUX MIXTURE. 



Bordeaux mixture, as has been known for years and frequently 

 demonstrated, is a powerful deterrent against flea-beetles and other 

 leaf-beetles, and its use should be continued. Since, as appears to be 

 demonstrated by the observations of Mr. Quayle, this flea-beetle is 

 quite discriminating in taste, it would be well to appW Bordeaux 

 mixture over a considerable surface and use Paris green or arsenate 

 of lead for the remainder of a field, i. e., to spray the majority of the 

 plants in such manner that those Avliich reject the Bordeaux mixture 

 on treated plants would resort to those spraj^ed with Paris green or 

 arsenate of lead. It should be determined which of these two insecti- 

 cides has the greater deterrent effect against flea-beetles. 



MECHANICAL AND CULTURAL :srETn0DS. 



Trap crops. — The great fondness displayed by this species for 

 rhubarb suggests the use of the latter between rows, e. g., in the vicin- 

 ity of woods, as an attraction or lure for the beetles, it being believed 

 that the beetles will concentrate on these j^lants and thus give the crops 

 an opportunity to grow to a sufficient height and strength to be able to 

 resist the ravages of the pest. Since certain cruciferous crops are 

 also attacked, such as turnips, it is further suggested that these and 

 other varieties like swedes and rutabagas, rape, and mustard be 

 employed. In the mild climate of the infested region all of these 

 can be grown during the winter, and it seems probable that kale will 

 be found equally effective. Beets, especially mangels, are grown in 

 the affected region and tests should be made with these as trap crops, 

 as also with sugar beet in regions where this crop can be grown 

 i:)rofitably. 



Rolling the fields. — One of the remedies attempted against this flea- 

 beetle in its occurrence in beet fields, as rei^orted by Doctor Ball, 

 consists in the use of rollers. He reports that " running a corrugated 

 roller over the field as soon as the damage is first discovered seems 

 55968°— Bull. 66—10 7 



