14 BITTER PIT INVESTIGATION. 



WATERING APPLE TREES WITH COPPER SULPHATE SOLUTION. 



The experiments were carried out at Burnley with Mr. McAlpine's co-operation. 

 Four varieties of apple trees were selected by Mr. McAlpine, all being susceptible to Pit, and with 

 bad reputations from previous years. They were " Gravenstein," " Williams' Favourite," " Charles 

 Ross," and " Jonathan" one tree of each variety. The strength of copper sulphate solution used 

 throughout was one in 100,000. 



This strength was based upon a publication by Ewart in the Proceedings of the Royal Society of 

 Victoria, Vol. XXVI. (1913), page 12, on the toxic limit for the growth of apple seedlings.* 

 Each tree received the following waterings : 



27th November 20 gallons between the four trees, 

 llth December 40 gallons between the four trees. 

 24th December 40 gallons between the four trees. 



8th January 40 gallons between the four trees. 

 22nd January 20 gallons between the four trees. 



The results are : 



Picked Yield Pitted Picked Yield Pitted 



"Gravenstein" ..18th Jan. 100 8 " Charles Ross" 25th Jan. 48 10 



" Williams' Favourite" 8th Jan. 10 " Jonathan" 13th Feb. 164 16 



Mr. McAlpine kindly supplied these figures. The " Charles Ross" were sent to me and kept 

 under observation for several weeks. No further pitting occurred. 



SUMMARY. 



It appears that the question as to whether apples are to Pit or remain clean is for the most 

 part decided before their starch is converted to sugar, that is, when for the most part they are still 

 on the tree. 



Laboratory experiments indicate some possible influence of the after treatment of picked 

 apples on the incidence of Pit, but the work requires to be greatly extended, with material which can 

 now be better recognised as suitable. 



Microchemical methods of detecting early Pit (before the browning stage) have not yet given 

 any special results, but the methods which may be suitably employed are discussed. 



No further evidence has been obtained to support the posioning theory of Pit. 



Experiments conducted with a view to producing Pit in apples by the absorption of poisons 

 in solution by the natural channels were negative in the laboratory, and inconclusive in the orchard. 



The orchard experiments require repeating on trees of Pit-susceptible variety, but with pre- 

 viously clean history. 



*Ewart places the toxic limit between 1 in 100,000 and 1 in 500,000. The strongest solution, 1 in 100,000, 

 was selected as it would be diluted by the water present in the soil. 



