24 BULLETIN 843, U. S. DEPARTMENT OF AGRICULTURE. 
the same material and formula as number 1. viz. 2 pounds of lead 
arsenate. 2 pounds of hydrated lime, and 50 gallons of water. 
Observations following these applications revealed a few dead 
larvae. To locate dead larvaB was a difficult matter. Our opinion is 
that many were killed at the first feeding. If not killed then or 
very soon after, they fed to maturity. Up to August 1 all remedies 
tried seemed to be equally effective, the amount of damage to the 
plant being about the same for each plot. Undoubtedly these in- 
secticides held the beetles and larvae in check. The 9-acre field had 
an unusually large number of hibernating beetles. After August 
1 the damage seemed to increase quite rapidly, and was worse on 
the Bordeaux plot than on any of the others. A small unsprayed 
plot was entirely destroyed, most of the injury here being done 
before August 1. 
A second spraying two weeks later, about July 25, might have 
almost if not entirely controlled the attack. 
In A. B. Owen's field of 9 acres, where spraying experiments 
were conducted July 10 and 11, the estimated damage was 12.5 per 
cent. It is believed that approximately 65 per cent of the larvae 
hatching before July 25 must have been killed by the lead arsenate 
or zinc arsenite. The number of adult beetles found in this field 
in early July undoubtedly was large enough to have damaged the 
crop to the same extent as in the special field mentioned above. 
This experiment, while not of the type anticipated, demonstrates 
that the attack of this species can be controlled by the use of either 
lead arsenate or zinc arsenite. 
A second spraying between July 25 and August 1 is recommended 
as very promising in controlling the insect, since it is at about this 
time that the second brood begins to appear. The two broods 
overlap, and the damage they do begins to increase very rapidly from 
this time on. 
The combination spray consisting of Bordeaux mixture and an 
arsenical is also a promising experiment. Undoubtedly the Bordeaux 
mixture, in case it proves a repellent against this insect, will serve 
as an important fungicide. It will add very little to the expense 
of spraying, and will possibly increase the yield several bushels per 
acre by controlling minor fungous diseases. 
ADDITIONAL COPIES 
OF THIS PUBLICATION MAY BE PROCURED FROM 
THE SUPERINTENDENT OF DOCUMENTS 
GOVERNMENT PRINTING OFFICE 
WASHINGTON, D. C. 
AT 
10 CENTS PER COPY 
