4 



added to sulfur dust so that the dust mixture would contain 5 per cent calcium 



caseinate. 



The copper dust (used only before the flower buds opened) contained 11 per 

 cent dehydrated copper sulfate. The suKur dust contained 92 per cent sulfur and 

 8 per cent inert ingredients. Wlien it was desired to apply an arsenical also to 

 dusted trees, a dust containing suKur and lead arsenate in the ratio 90:10 or 85:15 

 was used. 



Arsenate of lead and nicotine sulfate (Black Leaf 40) in the usual proportions 

 were added to the sprays for each appUcation, except for the fourth summer spray 

 when nicotine sulfate was omitted. 



The spraying was done with power sprayers with about 200 pounds pressure, 

 using Pilot rods or regular spray rods. 



The dusting was done with power dusters, either Perfect or Niagara. The duster 

 was driven along both sides of each row of trees, so that dust was applied to each 

 tree from opposite sides. Dusting is not a pleasant operation, because of the 

 pain caused by the sulfur getting into the eyes. Goggles, although somewhat of a 

 nuisance, appear to be a necessity when much dusting is to be done. Some difficulty 

 was experienced in thoroughly dusting the tops of tall trees. Krout (2) and Childs 

 (3) both mention this. The tops of taller trees cannot be thoroughly coated with 

 dust when any wind is blowing. The dusting was done early in the morning, be- 

 ginning about five o'clock in most cases. The foliage was not always wet, how- 

 ever. There is no experimental evidence of the necessity of dusting only when 

 the foUage is wet. 



Friez hygro-thermographs and rain gauges were maintained in the Frost and 

 Sabine orchards. The data on rainfall secured in the orchards is not considered 

 complete, and the precipitation data given in this report are from the Concord 

 observer for the United States Weather Bureau as recorded in Chmatological Data 

 for New England. 



Because of the large yield of fruit, it was manifestly impossible to examine every 

 apple in a plot at picking time. For this reason, four representative trees were 

 selected from each plot for examination of the fruit. About 150,000 apples were 

 examined. Since much of the infection was late, most of the scabby apples even 

 on the check plots were marketable. Apples designated as scabby in the data 

 include both marketable-scabby, and unmarketable scabby. 



Effect of the Addition of a Prepink Application to the Schedule. 



The delayed dormant appUcation is made just as the buds are breaking or when 

 the first tips of green show. The pink apphcation is usually understood to mean 

 that which is applied as soon as the blossom buds separate in the clusters, while 

 they show pink, but before they begin to open. Any appUcation of a summer- 

 strength fungicide made between the delayed dormant and the pink applications 

 may be spoken of as a prepink application. The interval between the prepink 

 and pink applications, which wiU depend upon the weather and consequent rapidity 

 of growth, is bound to be short. In the case of large orchards, there is Ukely to 

 be no interval, so that an appUcation begun as a prepink wiU end as a pink, as 

 regards the development of the flower buds. The first summer application, either 

 prepink or pink, should be made when the tree is first in danger of infection, that 

 is, before the first discharge of winter spores from the dead leaves beneath the tree. 

 It is probable that many of the failures to control apple scab in Massachusetts 

 have occurred because this first summer spray was too long delayed. The prepink 

 •cannot be regarded as a substitute for the pink appUcation. If a prepink appUca- 

 tion is necessary, a pink is none the less so, because new growth has exposed new 

 and unprotected leaf surface to the danger of infection. 



The beginning of the period when the tree is in danger of infection can be deter- 

 mined only by "trapping" the winter spores on adhesive-coated glass slides in- 

 verted over the dead leaves and microscopic examination of the slides, after the 

 method described by Wallace (4) and Childs (5). In some years, winter spores are 

 mature and ready to be discharged, if the dead leaves containing thern are wet, 

 while the apple buds are only beginning to swell. In such years, it is evident that 

 if the first application is deferred until the flower buds show pink, some infection is 



