18 



THE WESTERN CABBAGE FLEA-BEETLE. 



{Fhyllotreta pusilla Horn.) « 



In some of the Western States not inhabited to any extent by any of 

 the preceding species there is a small dark-colored flea-beetle uniformly 

 deep polished olive green, with the surface irregularly punctate 

 (fig. 11) which, as its English name indicates, affects more partic- 

 ularly cabbage and related crops. During 1901 it was observed doing- 

 considerable damage to sugar beet in portions of Colorado. It prefers 

 the younger plants, and as instance of its destructiveness one grower 

 reported that he had not raised a turnip for seven years on account of 

 its ravages. Between 10 and 20 acres of corn were reported destroyed 

 on one farm in twenty -four hours, the beetles sometimes coming in 

 swarms like black clouds and covering the plants. This flea-beetle 

 ranges from the Dakotas to Mexico, and westward 

 to southern California, being found in numbers at 

 high elevations in the Rocky Mountain region. 



REMEDIES. 



The arsenicals, especiall}- Paris green, are the 

 most useful remedies for leaf -feeding beetles, and 

 since Bordeaux mixture is extremely distasteful to 

 flea-beetles, this, if mixed with the insecticide and 

 applied as a spray, is more effective than when the 

 Fig. n.-Phyiiotreta pu- arsenical is used dry. Against some species, how- 

 .«t7?o— much enlarged evcr, Paris green mixed with 20 parts of flour and 



(after Riley, Divisfon i,i •i-i.iii.i, i £ i i-- £ 



of Entomology). dustcQ On inlestcd plants has been found satisiac- 



tor}", while kerosene emulsion and even strong soap 

 washes have been found useful in combatting others. When the plants 

 are quite young the spray can not be so well used as after they have 

 attained larger growth, but the dry mixture can then be applied with 

 best results. Bordeaux mixture used alone is valuable as a deterrent. 

 Clean culture is also of the greatest ^-alue. It consists in keeping 

 down weeds which serve as food for the beetles and as breeding places 

 for their larvae. Against the spinach flea-beetle we have to destroj'^ 

 the chickweed and lambsquarters of the vicinity and to avoid the 

 planting of beets and spinach in ground which has become overgrown 

 with these plants. For the pale-striped flea-beetle, lambsquarters, 

 cocklebur, and pigweed should be destroyed, while for insects like the 

 smartweed flea- beetle practically all weeds in the vicinity must be pulled 

 up and destroyed, as this insect feeds on nearly all forms of useless 

 vegetation. The time for performing this work varies according to 



« In early publications, for example, in the Report of thia Department for 188-t, p. 

 308, this insect was mentioned as Phyllotreta albionica owing to the fact that the two 

 species had not been separated, albionica being the older name. 



