5 



likely to occur before that time. Because a prepink application is proved necessary 

 or unnecessary one year, it does not follow that the reverse may not be true the 

 next year. A prepink apphcation made in the absence of information as to the 

 development and condition of the winter spores is to be regarded as insurance. 



Ivrout (2) in 1922 tested the addition of a prepink application to the spray sched- 

 ule. In the first orchard, the addition of the prepink apphcation was not followed 

 by a decrease in the percentage of scab but rather by an increase of 3 per cent. In 

 each of two other orchards the prepink spray apparently reduced the scab 1 per 

 cent. It is evident, therefore, that in 1922 no real benefit from the use of the pre- 

 pink spray was shown, as compared with a schedule wliich included only a pink 

 application before the flowers opened. 



In 1923, spray schedules with and without a prepink apphcation were tested in 

 two orchards. In the Frost orchard trees sprayed with lime-sulfur beginning with 

 the pink application yielded 7.06 per cent scabby fruit and when this material 

 was used beginning with the prepink application, there was only 1.2 per cent scab, 

 a significant reduction. Where Bordeaux mixture was used for the pink apphca- 

 tion, foUowed by hme-sulfur for the later applications, there was 1.7 per cent scabby 

 fruit, and on the plot where this schedule was modified by the addition of a pre- 

 pink apphcation of Bordeaux mixture, only 0.6 per cent scabby fruit was produced. 

 Here again there was a reduction in the percentage of scab, although such a small 

 one as to be probably without significance. 



In the Knights orchard, trees sprayed with dry lime-sulfur 4-50 beginning with 

 the pink application, yielded 1.7 per cent scabby fruit, and where dry lime-sulfur 

 3-50 was applied beginning with the prepink spray, there was 4.8 per cent scabby 

 fruit. Since the strength of the material was difierent the addition of a prepink 

 application was not the only changed factor affecting the control of the disease. 

 When the cost of the material and the cost of the labor for each application are 

 considered, however, it is evident that three apphcations of dr}'' Ume-sulfur 4-50 

 beginning with the pink were a more profitable treatment than four applications 

 of dry lime-suKur 3-50 beginning with the prepink. There. was 1.06 per cent 

 scabb)^ fruit on the trees sprayed with Bordeaux mixture beginning with the pink 

 application and dry lime-sulfur 4-50 for the later applications. As compared mth 

 this there was 4.9 per cent scabby fruit on trees sprayed with Bordeaux mixture 

 for the prepink and pink apphcations followed by liquid lime-sulfur for the later 

 apphcations. Since, as is shown elsewhere in this report, we may regard liquid 

 lime-sulfur as of equal fungicidal efficiency mth dry lime-sulfur 4-50, it is evident 

 that the addition of a prepink application did not reduce the percentage of scab; 

 instead, it was foUowed by an increase of 3.84 per cent. The need of a prepink 

 apphcation is not shown by the data of either 1922 or 1923. 



\Vhen we consider dusting, however, the case may be entirely different. In the 

 two orchards where the dusting schedule began with a prepink apphcation, a good 

 control of scab was secured. In the orchard where only one apphcation, the pink, 

 was made before the flower buds opened a much poorer control resulted. Satis- 

 factory experimental eAddence on this point, however, would necessitate that the 

 two schedules, with and without a prepink application, be used in adjoining parts 

 of the same orchard with one check for the two. 



The Use of Dry Lime-Sulfur. 



Arguments for and against the use of dry hme-sulfur as compared with the liquid 

 form include, of course, considerations of the relative costs, convenience in handling, 

 and effect on the pump. But the first question to consider is, does it control scab? 

 For if it does not, further consideration is needless. In the experiments here de- 

 scribed, trees spraj^ed with dry lime-sulfur 4-50, beginning with the pink applica- 

 tion, produced an average of 1.3 per cent scabby apples as compared with 60.7 

 per cent on the unspraj^ed trees. In the same orchards, on trees sprayed with 

 liquid lime-sulfur, the percentage of scabby apples was 2.7. The conclusion from 

 this is that dry lime-sulfur is fully as dependable for the control of apple scab as is 

 liquid lime-sulfur. 



In two successive years, Kjout (2) secured as good control of apple scab with 

 dry lime-sulfur as with the liquid. Gardner (6) found dry lime-sulfur as effective 



