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 

 larva?. To locate dead larvae 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 larvse 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. 



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