REMEDIAL MEASURES. 51 



Slingerland.^ These experiments from the fu-st gave entirely nega- 

 tive results, as the beetles could not be induced to feed on any kind 

 of foliage, either in the poison or check cages. Further experiments 

 were carried on, using such substances as bran, shorts, alfalfa meal, 

 and ground beet roots. The last bait was the only one which gave 

 any promise, and this proved successful only inider laboratory 

 conditions. Where the poisoned bait was applied in the cages a 

 few beetles were killed by it, but where it was tested in the field it 

 gave negative results. This was probably on account of the light 

 feeding habits of the adults and the abundance of food in the fields. 

 The ]>oisons used in the bait were Paris green, arsenite of zinc, arse- 

 nate of lead, and strychnine. 



FALL PLOWING FOR DESTRUCTION OF THE PUP^. 



The destruction of the ])up{? by cultivation, while probably it 

 has never been tested under field conditions, has been recommended 

 In' many students of this group because it is directed against the 

 most helpless stage of the insect. From observations made of the 

 results obtained by disturbing pupae in the laboratory cages, there 

 can be no doubt that this remedy would prove beneficial, since not 

 only would it break open many cells and kill the pupte mechanically, 

 but it would also disturb the rest so that they would come out earlier 

 in the spring and be subject to the attacks of their bird enemies. 

 This fall plowing would have to be quite deep (9 to 10 inches), and 

 very thorough, to be effective. 



The main objection to this remedy is that three or four years 

 must elapse before the benefits derived from it become apparent. 

 One point will serve to illustrate this. It was reported through 

 Mr. R. S. Vaile, the horticultural commissioner of Ventura County, 

 Cal., that in one instance, in a field which had been fall-jjlowed, the 

 wireworms were worse than in any of the surrounding fields. This 

 was doubtless true, and would have been possible had the plowing 

 killed every pupa. The wireworms which do the main damage for 

 at least the next two years are already in the soil at the time of the 

 plowing and are unaffected by it. This is true because the wire- 

 worms are not of sufficient size to be ver\^ injurious until the third 

 year. Mr. Vaile states that it is a rule with many of the bean grow- 

 ers in his county to fall-plow their fields; and that any benefits which 

 might have resulted from such a treatment have never been notice- 

 able. He adds, however, that the thoroughness of this plowing 

 might be improved upon in many cases. 



1 Bill. 33, Cornell Agr. Exp. Sta., 1891. 



