Apple Spraying Experiments in 1916 and 1917. 113 



Effect of the Different Sprays on the Foliage and Fruit 

 During the Summer of 191 7. 



No evidence of scab could be observed on the foliage and 

 fruit on any of the plots at the time of the second application, 

 June 20. The orchard was not visited again till July 9 when 

 the disease was present on the leaves in varying amounts on 

 all plots. The following is a summary of the record on each 

 for the season. 

 Plot 1. "T. P." arsenate of lead alone, double strength. 



Scab became common on the leaves and fruit as the season 

 advanced, but was very plainly less prevalent than on the un- 

 sprayed check. Relatively light leaf-spotting appeared about 

 August 1 and a month later this was fairly common but there 

 was little evidence of burning of the margins of the leaves. 

 Plot 2. Corona acid arsenate of lead alone, double strength. 



The amount of scab was similar to the preceding, but leaf 

 injury was somewhat more common. 



Plot 3. First application stronger lime-sulphur and acid ar- 

 senate of lead ; last two, double strength Corona acid 

 arsenate of lead alone. 



Throughout the season it was plainly evident that scab was 

 more efficiently controlled on this plot than on the two preceding, 

 which were sprayed with the two different forms of arsenate of 

 lead alone. There was also less scab here than on plot 5, which 

 received the standard treatment with combined lime-sulphur 

 and arsenate of lead. Leaf injury was relatively somewhat more 

 common than on the other two plots mentioned. 

 Plot 4. Standard dilution lime-sulphur and acid arsenate of 

 lead ; first application omitted. 



Somewhat more scab was recorded for this plot during the 

 summer than for plot 5. The most striking thing about it was 

 the small set of fruit. As the fruit neared maturity the con- 

 trast shown by the number of apples on the trees on plot 4 as 

 compared with those on plots 3 and 5 on either side was very 

 evident. Unexpectedly, leaf injury was more common than on 

 plot 5. 



Plot 5. Standard dilution lime-sulphur and acid arsenate of 

 lead. 



The conditions observed on this plot throughout the sea- 

 son did not differ materially from those on plot 2. 



