MISCELLANEOUS INSECTICIDE INVESTIGATIONS. 5 



As will be noted, while the triplumbio arsenate of lead was very- 

 effective against the larvae, it was somewhat slower in its killing 

 effect than the diplumbio and the mixture of diplumbic and triplumbic 

 arsenate of lead. This held true in the other experiments that 

 follow. Of the three commercial arsenates of lead, commercial (1), 

 which consisted of the triplumbic form, required a greater length of 

 time to kill the larvae than was required by the other two commercial 

 brands, which consisted mainly of the diplumbic form. 



Arsenate of iron, both chemically pure and homemade, was used 

 at double strength, owing to indications of slow killing effect in 

 previous tests. At this strength it was somewhat slower than 

 many of the other arsenicals. Like results will be noted in later 

 experiments with this material. 



The arsenates of zinc were effective and seemed to be safe to 

 use on the foliage. 



Arsenic sulphid, arsenic tersulphid, arsenic trioxid, arsenite of 

 lime, and the arsenites of zinc were effective, but burned the foliage 

 more or less seriously. 



Mercury bichlorid and zinc chlorid, while effective, were very 

 injurious to the foliage. 



All the other compounds were ineffective. 



Experiment II. 



COMPARISON OF THE KILLING EFFECT OF VARIOUS ARSENICALS AND DOUBTFUL STOMACH 

 POISONS COMBINED WITH LIME-SULPHUR SOLUTION ON LARVAE OF THE FALL WEB- 

 WORM. 



In Table II are given the results of using lime-sulphur at the rate 

 of 1J gallons to 50 gallons of spray in combination with all the 

 materials used. Little difference was noted from the use of these 

 combinations of lime-sulphur with the arsenicals. However, in 

 case of the materials which had no effect on the larvae when used 

 alone a marked difference was evident from the addition of lime- 

 sulphur. In all cases the larvae were killed, the length of time of 

 killing varying considerably with the material used. The difference 

 no doubt was largely due to the difference in chemical reaction 

 between the material and the lime-sulphur. Lime-sulphur alone 

 killed the 20 larvae in 15 days with only 0.73 square inches of foliage 

 consumed. In Table II are shown the results. 



