126 Maine Agricultural Experiment Station. 1918. 



ARSENATE OF LIME VS. ARSENATE OF LEAD. 



Arsenate of lime was used with the idea that when com- 

 bined with lime-sulphur less injury to the foliage and fruit 

 would result than is the case where arsenate of lead is employed 

 in the same way. As has already been stated the reverse seemed 

 to be the case with regard to foliage injury in 19 16, and no 

 differences could be noted between the effects of the two in 191 7. 



In 1916. a difference of only two per cent in russeting was 

 obtained when the results from the plot where the arsenate of 

 lime and lime-sulphur were compared with those from the check I 

 plot, while this difference where arsenate of lead was used was 

 over 46 per cent. In 191 7 the plots where these two treatments 

 were applied produced less russeted fruit than the unsprayed 

 check and the differences, although in favor of arsenate of lime, 

 were within the limits of experimental error. 



It will be seen that scab control was better on the arsenate 

 of lead plot in 191 6 but in 191 7 the results were quite the re- 

 verse of this Each season the percentage of merchantable ap- 

 ples obtained was decidedly in favor of the arsenate of lime. 

 No data has been obtained relative to the fungicidal value of 

 arsenate of lime used alone. 



SPRAY TREATMENT AS INFLUENCING THE SET OF FRUIT. 



Attention has already been called to the fact that the final 

 set of fruit on plot 4 in 191 7 was far below that of the plots on 

 either side of it. There is nothing in the condition of the trees 

 on these plots which could in any way account for this difference. 

 In the writer's opinion the only explanation for the small crop 

 on this plot is that it was in some way, directly or indirectly, 

 concerned with the failure to make a spray application at the 

 time the blossom buds were showing pink. This was the fifth 

 season that a plot treated in this way had been included in this 

 series of experiments and, with the possible exception of 1913.. 

 nothing of the kind had occurred previously. 



A number of different observers have stated that loss of 

 fruit set may often be traced directly to the fact that the scab 

 disease may occur abundantly on the pedicels and that this 

 causes the blossoms and young fruit to fall. Wallace in 191 3 



