FIFTY-FIRST ANNUAL REPORT. 65 



reduced the yield and lowered the quality of the fruit. I have recently 

 found one report of similar trouble on sweet cherries where it was found 

 that strongly alkaline sprays reduced the size of the fruit by causing 

 in some way a serious loss of water from the fruit, with the resulting 

 decrease in size. This trouble seems worthy of further study as it may 

 be of considerable importance under some conditions. 



It may be well to compare this years results with those gotten last 

 year in the same orchard. In 1920 the weather was more favorable to 

 leaf spot development and nuicli of it developed by July 1st. Bordeaux- 

 gave best control, lime-sulphur second, and the dusts ranked somewhat 

 lower but the Bordeaux trees lost much foliage in midsummer as the 

 result of Bordeaux injury. The results, then, for the two seasons show 

 that the liquid sprays gave best control of leaf spot the first year but 

 with considerable Bordeaux injury to the foliage and the second year 

 all materials gave equally good control of leaf spot; but the physical 

 condition of the dusted foliage was better and there was the added 

 trouble of stunted fruit on the Bordeaux trees. One factor which may 

 have had some influence on the better results with dust this year was 

 that all dusting was done under very favorable conditions and further, 

 it must be stated that weather conditions were much less severe than 

 in 1920. 



PRE-PINK SPRAYING OF APPLES. 



The control of apple scab has not been as successful in many instances 

 as was desired. It was not known whether the trouble was that the 

 sprajdng schedule was wrong or whether it was simply faulty application. 

 Those of you who are familiar with the life history of apple scab know that it 

 is carried through the winter on the leaves on the ground. It goes 

 through certain changes and after it has reached a certain stage further 

 development is dependent upon proper conditions of temperature and 

 moisture. When the right conditions prevail, the scab spores are dis- 

 charged and carried to the trees. It has always been thought in Michi- 

 gan that the regular pink or cluster application is early enough to pre- 

 vent the first or primary scab infection but the results in several of my 

 spraying experiments have indicated very strongly to me that if weather 

 conditions are right, this infection occurs earlier than the pink stage of 

 our earliest blooming varieties. I discussed this matter with Dr. Coons 

 who became interested in the problem and with the result that Mr. 

 Bennett of the Botanical Department made studies to determine just 

 how early the first infection might occur. Leaves were collected daily 

 from the Duchess orchard of Mr. J. C. Maynard, near the Graham Ex- 

 periment Station, by Mr. Hootman and were sent to the college for 

 examination by Mr. Bennett. I do not care to discuss in detail the 

 results of these studies but will say that they showed the scab spores 

 were mature and ready to discharge this year long before the Duchess 

 blossoms were in the pink or cluster stage. This work will be continued 

 next year. 



In this same orchard I arranged a spraying experiment so as to get 

 accurate information in this way. The orchard was divided into three 

 plots and treated as follows : 



1. Check plot. No treatment. 



2. Regular schedule beginning with the pink or cluster application. 



3. Special schedule with a pre-pink application. 



