PROCEEDINGS, 1916. 43 



at once. When one consides the reaction that takes place when arsenate of lead is add- 

 ed to sodium sulphide the cause of the burning is clear. The lead arsenate breaking up 

 in the solution to form lead sulphide results in the formation of a correspond ng quan- 

 tity of arsenate of soda, which, being entirely soluble, is responsible for the burning. 

 When arsenate of lime is added to sodium sulphide no chemical change occurs and the 

 combination is less harmful to foliage than the arsenate of lime used alone. 



On vigorous, strong growing trees whee an abundant supply of nitrogen is avail- 

 able, the sodium sulphide arsenate of lime combination is comparatively harmless even 

 where used three or even four times, but when the trees are not growing very rapidly 

 the continued use of the combination seems to cause the leaves to become poisoned, 

 yellowing the foliage and causing a very slight amount of burning, so that a proportion 

 of the leaves fall to the ground. In all orchards where this combination was used but 

 once during the season the injury was very slight, and the foliage for the most part 

 seemed improved being smoother and darker green in color than when unsprayed or 

 sprayed with other solutions. It would seem possible that in most orchards where in- 

 sect conditions indicated the necessity of a very rapid killer, that the sodium sulphide- 

 arsenate of lime combination could be used with comparative safety at least once in a 

 season, but further work will have to be done before even that can be generally recom- 

 mended. 



FUNGICIDAL VALUE. 



In March, 1915, Prof. W. J. Morse of the Maine Agr. Expt. Station published Bul- 

 Tetin No. 249 "Six Years of Experimental Apple Spraying at Highmoor Farm." In this 

 publica'ion Prof. Morse notes the high fungicidal value of arsenate of lead, the ordinary 

 amount, 1 lb. of dry acid lead arsenate to 50 wine gallons of water, showing marked 

 fungicidal value and double that amount or 2 lbs. to 50 wine gallons being in many in- 

 stances equal in value to some of the recognized fungicides. For years it has been ar- 

 gued by institute speakers etc., that arsenate of lead increased the value of fungicides 

 but from what authority they spoke I have never been able to learn. 



Whether arsenate of lead or arsenate of lime is of greater value as a fungicide in the 

 lime sulphur solution is an open question. On the one hand where we use lead arsenate 

 with lime sulphur we have, when we spray it on the trees, 35 per cent less sulphur in so- 

 lution, most of the arsenic in the form of arsenate of lime, a small quantity of arsenate 

 of lead remaining as such, and a quantity of lead sulphide. On the other hand where 

 we use arsenate of lime with lime sulphur we have no loss of sulphur in solution and 

 the arsenate of lime going on the trees as such. 



In 1915 a few results were obtained but as they were on a comparatively small scale 

 they may be taken as indicative rather than conclusive. 



