92 



BITTER PIT INVESTIGATION. 



B. — PRUNING EXPERIMENTS. 



While Bitter Pit may occur on both pruned and unpruned trees, it is nevertheless desirable 

 to test the relative effects of severe, light, and leader pruning, as well as no pruning at all, on this 

 disease. In the experiments hitherto carried out in Victoria, the Principal of the Burnley School 

 of Horticulture has kindly pruned the trees, so that in the different experiment orchards there is 

 a regular gradation observed between those trees of the same variety severely pruned and those left 

 without pruning. 



In South Australia, Mr. Quinn is testing the influence on this disease of winter and summer 

 pruning, with and without the thinning of fruit, as compared with trees never pruned and fruit not 

 thinned. 



Root pruning will also be attended to, although in our variable climate, in cases where the 

 orchard is dependent upon the natural rainfall, there is a danger of such trees suffering, at a critical 

 period of their growth, from a diminished water supply. 



The tree chosen for this experiment is of the Prince Bismarck variety, eleven years old, and 

 very liable to Pit. It was rooted out on 19th June to show the nature and spread of the 

 root-system (Fig. 133), and replaced after cutting back the roots to within 3 feet of the trunk. 

 Fresh sandy soil was supplied, with the addition of 4 lb. of blood manure and bonedust around 

 where the roots were pruned, and about 1 cwt. of well-rotted stable manure mixed with the 

 soil. 



This tree was dug out by the roots to show the relation between the shoot-system and the 

 root-system. The soil is loamy for 15 inches, with a stiff clay subsoil. The tree was about 10 feet 

 high, with a spread of 5J feet each way. There was no tap-root, and the longest roots extended for 

 12 to 14 feet, and passed through the stiff clay. 



If a scientific system of pruning could be adopted, combined with judicious thinning, so as 

 to prevent the regular recurrence of heavy and light yields, and give a regular, even, steady growth 

 of fruit from season to season, it would tend in the direction of lessening the Pit. 



5. At Burnley Horticultural Gardens. 



These gardens are only about 3 miles from Melbourne, and are very conveniently 

 situated for experimental work. They are 50 feet above sea-level, and about 3| miles distant 

 from the sea. They owe their origin to the Royal Horticultural Society of Victoria, which was 

 established in 1849, and one permanent result of the efforts of its members was the 

 experimental gardens, now associated with a School of Horticulture, under the Department of 

 Agriculture. 



They contain a large and valuable collection of fruit trees, and of apples alone there are 

 672 varieties under observation. Such a collection, accurately named, and with the history of 

 most of the trees known, is of inestimable value in connexion with the investigation of Bitter 

 Pit, more particularly as this disease is more or less prevalent every year. I am also 

 fortunate in that the Principal, Mr. E. E. Pescott, has taken a lively interest in the progress of 

 this investigation, has cordially co-operated with me in every line of experiment, and has carried 

 out the work in connexion with pruning and stocks as far as the resources of the gardens would 

 allow. 



Manurial experiments have not been carried out here, since from the very object of the gardens 

 being to have a standard collection of fruit trees, there is no single variety largely represented by 

 numbers. The majority of the apple trees are on the dwarf system, because it was found necessary 

 to economize space, in order to make provision for the existing collection, as well as the addition of 

 new varieties. The Paradise stock is considered the most suitable for dwarfing purposes, but, owing 

 to its liability to Woolly Blight, a system of double grafting has been tried. In season 1888-9 it 



