DUSTING AND SPRAYING EXPERIMENTS OF 1918 AND 1919. 21 



In comparing the percentages of scabby fruit on any of the plots it will 

 be well to consider the following facts. In the spring the blossom buds 

 opened slightly, just enough so that the individual buds could be easily 

 distinguished, and remained in this condition for a week or more be- 

 cause of cold weather. During this period conditions were very favor- 

 able for scab development. No dusting or spraying was done until the 

 buds had separated into the cluster stage. 



When the fruit was harvested and counted, there was found on the 

 apples from all plots an early infection of scab. This scab was in small 

 spots which were on or partly on the calyx lobes. On fruit from the 

 dusted plot there was very little scab of any later infection. On fruit 

 from the plot sprayed with lime-sulphur solution there was a small 

 amount of scab on other parts of the apples. In all the dry lime-sulphur 

 and 15. T. S. plots there was much more on other parts of the apples. 

 The later infections had nearly always developed with larger spots. 



This early infection undoubtedly occurred before the first application 

 was made. On the plots treated with sulphur dust and lime-sulphur 

 solution there was very little scab of any later infection. This condi- 

 tion indicates two things: (1) an early or "pre-pink" application would 

 have prevented the early infection of scab and (2) sulphur dust and 

 lime sulphur solution prevented practically all development of later in- 

 fections but the dry lime-sulphur and B. T. S. did not. 



A TEST OF SEVERAL ARSENATES ON APPLES 



A block of mature Stark trees was used for testing several arsenates. 

 This block of Stark trees is part of an orchard of several varieties be- 

 longing to Mr. A. D. O'Brien and is located about three miles west of 

 Grand Rapids. 



Materials. The block of trees was divided into four plots of about 

 nine trees each and each plot was sprayed with a different poison. The 

 materials and the strengths at which they were used are listed here : 



Plot 1. ' Corona calcium arsenate (dry), 1 lb. in 50 gal. with 3 Ibs. 

 hydrated lime added. 



riot 2. Corona lead arsenate (dry), 11/4 Ibs. in 50 gal. 



Plot 8. Dow magnesium arsenate (dry), 114 Ibs. in 50 gal. 



Plot 4. Xiiliexforin lead arsenate (dry), 1% Ibs. in 50 gal. 



Two tiers were left uusprayed as checks. 



Lime-sulphur solution, diluted at the rate of 1 to 40, was used in com- 

 bination with all the poisons, for all applications. Black Leaf 40 was 

 used on all plots for the first application. The arrangement of the trees 

 and plots is shown in Chart VI. 



Applications. Four applications were made according to the regular 

 schedule. 



1st. The pink or cluster application. 



2nd. Immediately after petals had fallen. 



."i'd. Two weeks after second. 



4th. July 30th. 



All spraying was done with a spray gun and with 200 to 225 pounds 

 pressure. 



