SPRAYING EXPERIMENTS AND APPEE DISEASE^. II 



DISCUSSION OE RESUETS. 



The experiments of the present year were designed, in a 

 measure, to supplement the data O'btained in 1912, hence in the 

 discussion of the results obtained this year it is necessary to 

 take into consideration certain of those obtained last year and 

 reported in Bulletin 212. 



Efficiency of the first spray application. It is claimed by 

 some that the spray application made when the buds are show- 

 ing pink is the most effective one in controlling apple scab. 

 That this may be the case was shown in a most striking manner 

 in 1912. Where this spray (lime-sulphur) was omitted only 

 about 50 per cent of perfect apples were obtained and over 

 47 per cent were scabby. Where it was applied nearly 90 per 

 cent of the fruit was sound and perfect and less than 1.5 per 

 cent were scabby. The general conclusion was that, under the 

 climatic conditions which prevailed that season, the two later 

 sprayings paid little more than the cost of application. Atten- 

 tion was called to the fact that while this is important as show- 

 ing the value of the first spraying it should not be taken as 

 implying that the two later sprayings should be omitted. 



The results secured in this part of the 19 13 experiment would 

 seem quite contradictory to those obtained the previous year. It 

 will be noted on reference to the table that While the figures 

 favor the plot where all three applications were m.ade these 

 differences are probably within the limits of experimental error. 

 Plot 4 produced only about 4 per cent less perfect apples and 3 

 per cent more scab than plot 3. 



It is difficult to account for this failure of the omission of 

 the first application of the spray to show greater differences in 

 the line of scab control. Had there been an excessive amount 

 of scab on both plots witli only this amount of difference it 

 would be fair to assume that the period which elapsed between 

 May 8 and the time of the second spraying allowed the disease 

 to become established. As a matter of fact when compared 

 with plot 7, or the unsprayed check which gave nearly 40 per 

 cent of scabby apples, it will be seen that scab control was 

 quite efficient even in the case of plot 4. An explanation o^f the 

 results which seems very probable i; that while the warm period 

 the latter part of x^pril and the first of May was sufficient to 



