February, '22] sanders: cheaper arsenicals 71 



Mr. Glenn W. Herrick : Is powdered arsenate of lead less effective 

 in controlling this beetle than arsenate of lead in liquid form? 



Mr. William Moore: I did not mean to leave that impression. 

 We have more or less passed by the dust because it gives uncertain 

 results. One can get one result one day and another result the next. 

 The dust when applied by the cloud method only covers a portion of 

 the leaf surface, and fails to kill. The beetle fails to eat a sufficient 

 amount before it leaves the plant. 



Mr. R. L. Webster: Have you specific data on the grams of arsenate 

 per square meter of leaf surface? 



Mr. William Moore : I have not at the present time. We intend 

 to determine it during the coming season. 



Mr. N. F. Howard: Our results with the Mexican bean beetle 

 corroborate Doctor Moore's, especially in the case of lead arsenate. 

 In confinement, adults placed on sprayed plants are more easily poisoned 

 in spring and stimmer than late fall, when very low percentages are 

 poisoned. This does not apply to the larvae however. 



President George A. Dean: The next paper on the program is 

 by G. E. Sanders and A. Kelsall. 



CHEAPER ARSENICALS AND THEIR USE 



By George E. Sanders and A. Kelsall, 

 Insecticide Investigations, Entomological Branch, Ottawa 



In considering cheaper arsenicals, w^e can pretty well confine our 

 attention to arsenate of lime and white arsenic, since arsenic, in the 

 form of arsenate of lime varies in cost from one-half to three-fourths 

 of that in the form of arsenate of lead or Paris green, while arsenic 

 in the form of white arsenic, varies in cost from one-seventh to one- 

 tenth of that in the fonn of arsenate of lead or Paris green. 



One or the other of these two cheap arsenicals can be substituted for 

 the more expensive ones for the m.ost ordinary purposes, with the 

 exception of — (1) Lead hydrogen arsenate for straight sprayinp- and 

 dusting on tender foliage, and for combining with sulphur dust. (2) 

 Neutral lead arsenate for use on the most tender foliage, and for use in 

 lime sulph-ur solution where arsenate of lime gives injury when combined 

 with it. 



Arsenate of Lime 



This material dusts and sticks better than Paris green, is much 

 safer on foliage, and with the exception of its use in paint should wholly 

 replace that well known material. 



