EXPERIMENTS CONDUCTED WITH A VIEW TO CONTROLLING DISEASE. 37 



In the typical experiments carried out at Deepdene, near Melbourne, on the principle of a regular 

 gradation from no pruning, through leader and light, to severe pruning, the pruning was done each 

 succeeding year by Mr. E. E. Pescott, F.L.S., and therefore there was uniformity throughout the 

 operations. 



Since the striking results obtained in the checking of Bitter Pit by a particular type of pruning 

 has created widespread interest, I am giving full details of the experiments, together with illustrations 

 of the two contrasted systems of light and severe pruning. 



The description of the methods pursued by Mr. Pescott is given in his own words : 



"Mr. Me Alpine decided to include pruning within the scope of his enquiry and experi- 

 ments, it having been stated for years that if the apple tree were allowed to pursue its natural 

 growth unchecked by the force of pruning, little or no Bitter Pit would result in the fruit. 



"Further, it had been stated by some growers that there was less Bitter Pit in the fruit 

 on trees which had been allowed to retain an extensive lateral system, and that both Pit and 

 'crinkle' were very prevalent in such varieties that were pruned so as to produce spurs on 

 the leaders and sub-leaders, e.g., the London Pippin. 



"Hence it was decided to select a row of London Pippin apple trees which were growing 

 in the Burnley Horticultural Gardens, and submit them to an exhaustive comparative 

 pruning test. The trees had been allowed to develop a good lateral system throughout in 

 the season previous. In designing the experiment, commercial pruning, or rather pruning 

 these London Pippin trees according to the system in vogue in most orchards, viz., pruning 

 off all laterals and filling the leaders and sub-leaders with spur systems, was not considered. 

 Indeed it was necessary to have a good lateral system on each tree for comparative purposes, 

 and also to consider the suggestion previously referred to, that less Pit developed upon the 

 laterals than upon the spur systems. 



"The trees were separated into four sections, and three types of pruning in regard to 

 the lateral system were designed : 



(1) The laterals and leaders were all to be severely pruned, leaving short spurred 



laterals. 



(2) The laterals were to be lightly pruned and left considerably longer and more 



extensive than in the first section. 



(3) The laterals were to be left entirely unpruned, pruning and thinning out the 



terminals of the leaders and sub-leaders, so as to retain their strength of 

 character and to stimulate their growth. 



(4) To provide a check on the three sections, a fourth section was left quite 



unpruned during the whole course of the experiment. 



''From the Figs. 59 and 60 the comparison between the severe and light systems of 

 pruning will be readily noted. 



"In Fig. 60, illustrating severe pruning, the laterals have all been pruned and repruned 

 back, so that very few of them are more than nine or ten inches in length. In addition, 

 several have been entirely removed from the leader. 



"In Fig. 59, illustrating light pruning, the laterals have been left considerably longer, 

 averaging from one foot to two feet in length, and even longer in some cases. 



"The comparison, therefore, is that in one the laterals are severely cut back, and in the 

 other they are much less interfered with." 



This contrast between light and severe pruning of the London Pippin might also be put to the 

 test by means of pot experiments. 



6. AT BURNLEY HORTICULTURAL GARDENS, VICTORIA. 



This is the fifth consecutive year in which the London Pippin has been pruned on a definite system. 

 There was a good average crop in all the plots, but on account of the small size of the fruit there was 

 not sufficient Pit to discriminate between the different systems. 



The trees are now about/ 14 years old, on Northern Spy stocks, and were pruned on 31st August, 

 1915, The fruit was picked on 21st March, 1916, with the result shown in the following table : 



