62 BITTER PIT INVESTIGATION. 



Experiments on a limited scale show that the yield was increased and the amount of Pit consider- 

 ably reduced when sulphate of iron was applied at the rate of one to two pounds per tree. 



There are two series of experiments which were initiated at the commencement of this investiga- 

 tion, and which may be found to help considerably in reducing the Pit, but from their very nature 

 require a considerable time to yield reliable results. 



I refer to the experiments with stocks and the pruning experiments, combined with thinning of 

 the fruit. 



The stock experiments are being conducted at the School of Horticulture, Burnley, and the trees 

 are enclosed in a bird-proof screen, so that the fruit is not interfered with by birds nor other animals. 



The trees are now coming into bearing, being five years old from planting, and with the crop 

 carefully gathered and the percentage of Pit determined for at least five seasons, the effect of the stock 

 on the development of Pit will be demonstrated. 



Through the courtesy of the Director of the Royal Gardens, Kew, England, I have received a 

 supply of pips and cuttings of the Wild Crab apple of Britain, and these will also be tested as stocks 

 with different varieties of marketable apples. There is a possibility that the stock might affect the 

 scion in such a way as to render the variety comparatively immune to the disease. 



A valuable series of stock experiments are also being carried out by Mr. Quinn at the Government 

 Experiment Orchard, South Australia. These trees are of various ages, and some of them are now 

 beginning to produce a fair crop. The thinning experiments carried out by Mr. Quinn may also 

 prove of commercial value. Early thinning may aid in the setting of fruit-buds for the following season, 

 and thus ensure a fair crop every season in the case of varieties that tend to bear alternate years. 

 In order to minimize Bitter Pit in a variety subject to it, it is desirable to encourage regular bearing, 

 and with regular thinning there is a possibility of inducing the habit of annual bearing, instead of having 

 an "off" season. Experiments such as these can only be undertaken in connection with institutions 

 which are likely to continue in existence for a long series of years. A beginning has been made in the 

 Government institutions of the School of Horticulture, Burnley, and the Experiment Orchard, South 

 Australia, and it lies with those in authority to see that the work is carried .to a successful issue. 



We have already shown, in an experimental way, that the apple attains its full size at least a 

 fortnight before it has fully matured ; that by means of light pruning the amount of Pit is considerably 

 reduced ; that under irrigation conditions the least Pit occurs when the trees are lightly watered 

 throughout the season, and the greatest amount of Pit when water is too liberally applied late in the 

 season ; and that in cold storage a uniform and constant temperature of 30-32 degrees Fahr. retards 

 the development of Pit and arrests the ripening process. Bailey, in his Principles of Fruit Growing, 

 recommends that "in the case of apples, it is generally best to pick them, if they are to be stored or 

 exported, j ust as they have arrived at their full size and when they have attained only a part of their 

 full colour. Apples which are picked slightly green, however, generally continue to keep well after 

 being taken from cold storage." 



From these experiments we are fully justified in recommending 



(1) For export purposes, to pick the fruit when it has reached its full size, but before it is 



fully ripe. 



(2) With Pit-liable trees at least, to prune as lightly as possible when the bearing stage is 



reached, having regard to the bearing capacity of the tree, the vigour of its growth, and 

 the symmetrical development of its laterals. 



(3) When irrigation is practised, to water lightly throughout the season, according to require- 



ments and in order to keep the trees steadily going. 



(4) In oversea shipments it is necessary to maintain a constant and uniform temperature of 



30-32 degrees Fahr. The most successful shipment of apples from Australia was carried 

 out on this principle. At the bottom of the hold there was a layer of six inches of saw- 

 dust, and the sides were lined with vegetable matting as a good non-conductor of heat. 





