THE HOP FLEA-BEETLE. 87 
that unskilled laborers are likely to make imperfect emulsions and 
waste the material in applying it. With competent help, and other 
things being equal, kerosene-soap emulsion should be the more eco- 
nomical spray. It would be well 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 apply 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 which reject the Bordeaux mixture 
on treated plants would resort to those sprayed 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 METHODS. 
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 plants 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 a- trap crops, 
as also with sugar beet in regions where this crop can be grown 
profitably. 
Rolling the fields. — One of the remedies attempted against this flea- 
beetle in its occurrence in beet fields, as reported 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 
