80 Agricultukal Experiment Station, Ithaca, N. Y. 



in cages containing clover and timoth}'. Thus our experiments do 

 not indicate tliat a crop of mustard will render the soil so free 

 from wireworms that the succeeding crop will escape their ravages. 



rape. 



Another crop, upon M'hich it is said wireworms will not feed, is 

 rape. It is but little grown in America, but is considerably grown 

 in England to provide pasture that will fatten sheep readily. 



Wireworms lived as long and thrived as well in our breeding 

 cages on roots of rape as in soil in which clover and timothy Avere 

 grown. Thus, it would seem that rape can no more be regarded as 

 an immune crop than any other crop cultivated at the same time. 



2. Destruction of Wireworms by Means of Insecticides. 



As the sjjecies of wireworms which infest growing crops live dur- 

 ing their whole larval life beneath the surface among the roots, it is 

 a more difficult matter to reach them with insecticides than those 

 pests which feed exposed on the plants. A substance must have 

 great penetrating and killing power to be of any value. Iklost of 

 the substances that have been recommended were iirst applied 

 merely as fertilizers, but in later years their insecticidal properties 

 also have been much discussed. 



(a) Substances that act merely as Insecticides. 



Most of the insecticides which we used are well known and 

 have been used successfully against other underground insects. 



kerosene, pure and as an emulsion. 



In 1885, Professor Forbes found that " applications of these 

 substances made to wireworms in the earth were found practically 

 ineifective, any strength sufficient to kill them killing vegetation 

 also." Oar experiments corroborate Professor Forbes' conclu- 

 sion. We found that wireworms could be killed by using either 

 substance in sufficient quantities, but this amount would destroy 

 all vegetation and would be too expensive an application, 



CRUDE PETROLEUM, PURE AND AS AN EMULSION. 



On the whole our results with the crude petroleum emulsion 

 and with the crude petroleum were not as promising as those 

 obtained with the kerosene oil emulsion. 



