Proceedings, I'M'-l. 15 



Willi the (■(iiiihinatioii sprays (lie enlii-o loaf was destroyed, or else the injury 

 covered a distinct porlioii, all iiarts of which were discoloured. Scah-spots on the 

 leaves appeared black, ordinary leaf-tissue hrown. 



With the arsenite of zinc only the scab-spots were injured. In a few cases 

 entire leaves were blackened or browned. The majority of the injured leaves were 

 spotted with injury. Each one of these spots was determined to be the seat of 

 germination of a scab-spore. The leaf-tissue between and surrounding these spots 

 did not appear to be injured. 



Arsenate af lead (acid) and arsenate of tcad (non-acid ) did not cause injury 

 in any case. 



The tree siirayed with water did not show injury. Tlie injury did not besin to 

 show U|i badly for about five days, when suddenly, overnight, it aii]>earcd .-it its 

 worst. 



As soon as the injury on trees sprayed with arsenate of lead (nou-acid)4- 

 lime-snlphur 1-30 became apparent, checks were made on different trees of the same 

 block. The cheek sprays were the same as ou the trees 10, 12, 13, lo, 10, IS. The 

 utmost care was used in these applications, and as the same injury occurred a 

 second time, we must conclude that, even with the purest of chemicals, lime-sulphur 

 -f- arsenate of lead is not a stable spray under North-west conditions. 



The controlling factors are yet to be determined. Two other e.\periments for 

 the control of the codling-moth have not yet been finished. But in one of these lime- 

 sulphur + arsenates of lead, acid and uon-acid, and arsenite of zinc did not cause 

 more than slight injury at the tirst application. The second application on June 30th 

 caused serious injury. Therefore we may say that the above combination sprays are 

 safe for the calyx spray, but are unsafe at the time of the second codling-moth 

 spray.* 



Recent Insecticide Investig.\tioxs. 



(1.) To tind the value of lime-sulphur as a stomach-poison. 



(2.) To find the value of arsenate of lead (acid) as a stomach-poison. 



(3.) To find the value of arsenate of lead (non-acid) as a stomach-poison. 



(4.) To find the value of arsenite of zinc as a stomach-poison. 



(,">.) To find the value of arsenate of lead (acid) -f- lime-sulphur as a stomach- 

 poison. 



(0.) To tind the value of arsenate of lead (non-acid) -|- lime-sulphur as a 

 stomach-poison. 



(7.) To find the value of arsenate of lead as a stomach-poison. 



The chemicals used were secured from the same source as those used in the 

 spray-injury experiments. 



Larvre of the tent-caterpillars Maiacusoma crosa. and Malaca.soina iiluriatis were 

 used in these experiments, and were placed on sjirayed twigs in the open part of the 

 insectary. Newspapers were placed under the twigs to catch the dead larva; and 

 every experiment kept sejiarate from the rest. 



tiitinmari/ of licsatts. 



In these experiments arsenite of zinc was a quicker-acting poison than arsenate 

 of lead, acid or non-acid, and remained in suspension much better. .\cid arsenate 

 of lead was a quicker-acting poi.son than the non-acid .'ind remained in sus))ension 

 better. 



Non-acid arsenate of lead was slow in its action, but was satisfactery in that 

 death finally occurs. 



Lime-sulphur In our experiments iias not proven to be much value as a stomach- 

 jioison. 



Limesulpluir with arsenicals seems to retard to a moi'e or less extent the action 

 of the iioison, and it is possilile for larvre to feed ou foliage spra.ved with weak 



• .\rsonilc «f zinc is npparontly iint pntiri'ly satlsfactor.v under .ill conditious. and should 

 not bo used until after niore-expcriniental work has been done. 



