2S CIRCULAR 639, U. S. DEPARTMENT OF AGRICULTURE 
to the wrapper crop in the past. All the methods of control, both 
direct and indirect, suggested in this circular should receive serious 
consideration, for they. hhave an important bearing on the problem. 
Plant beds should be located as far as practicable from tobacco 
fields. The moist soil under the plants, which is not disturbed ex- 
cept by weeding, furnishes an excellent breeding place for the next 
generation of beetles. A very slight infestation of a bed by over- 
wintered beetles can often produce a surprisingly large number in 
the next generation, which may attack the tobacco in any nearby field. 
If the bed is located at some distance, this danger is considerably 
lessened. Flea beetles on plant beds should be controlled by the 
methods previously described. 
As the tobacco flea beetle feeds on and multiplies to a limited extent 
on a number of wild plants, all weeds in and around the edges of 
tobacco fields should be destroyed as far as possible. 
One of the most important cultural methods of controlling the flea 
beetle is the complete destruction of all tobacco stalks and stumps 
immediately after the crop is harvested. The removal of the main 
food supply at this time prevents continued breeding of the insect 
and is unfavorable for those individuals that enter hibernation. 
THE APPLICATION OF INSECTICIDES 
While the feeding by the overwintered beetles (fig. 31) in most in- 
stances causes little damage to the newly set plants in this region, the 
egos produced by relatively few beetles are a potential menace to a 
wrapper-tobacco crop. For this reason it is a wise precautionary 
measure to apply an effective insecticide soon after the plants are set, 
even though very few beetles are in evidence (fig. 32). 
A very s satisfactory control for flea beetles on tobacco is a dust con- 
taining 1 percent of rotenone derived from derris or cube root. These 
rotenone- bearing dusts kill flea beetles quickly and are harmless to 
tobacco plants. a disadvantage of the rotenone dusts is the fact that 
they exert no appreciable control on grasshoppers, which frequently 
attack tobacco. Grasshoppers may be controlled effectively, however. 
by means of the poisoned bait described on page 39 of this circular. 
Commercially prepared dust containing 1 percent of rotenone may 
be obtained, or a home-mixed dust can be made by mixing 25 pounds 
of derris or cube powder (containing 4 percent of rotenone) with 
75 pounds of sterilized tobacco dust as a diluent. 
If the rotenone content of the derris or cube powder is greater or 
less than 4 percent, the proportion of the diluent must be varied 
accordingly. The powder should be of such a degree of fineness that 
not less than 90 percent of it will pass through — a sieve having 200 
meshes per linear inch, and all the material should pass through a sieve 
having 80 meshes per linear inch. 
The quantity of dust applied during an application should be goy- 
erned by the size of the tobacco plants. From the date the plants 
are set until they are about 18 inches high a dosage of 3 to 5 pounds 
per acre should be sufficient, whereas mature tobacco may require 8 
to 10 pounds per acre. An efficient rotary duster capable of giving 
even distribution should be used. When the plants are not over knee 
high the dust application is most effective when the nozzle of the dust 
gun is directed toward the foliage and in front of the operator (fig. 
