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BITTER PIT INVESTIGATION. 



APPENDIX II. 



BITTER PIT INVESTIGATION. 



Circular No. 2. 



I. — MANURING. 



Experiments to be conducted with trees of the same variety, similar in age and size, all in bearing, and liable to 

 Bitter Pit. S 



The object of these manurial experiments is primarily to test the effect of different manures on the development of 

 Bitter Pit, but, incidentally, they will show what manure gives the best yield. 



Experiments in the manuring of fruit trees have hitherto been comparatively neglected in Australia, and, if carried 

 out properly in the different States for three or four seasons at least, they should yield valuable results. A well-balanced 

 ration is just as necessary for the healthy growth of the plant as for that of the animal, and, where an excess of nitrogen is 

 applied, the Bitter Pit is found to be more prevalent. On the other hand, in applying bone dust alone, as is often done, 

 some of the essential plant foods are omitted. 



The manures should be well worked into the soil, so as to bring them within reach of the feeding roots of the tree, 

 and, in well established trees, the fertilizer should be equally distributed, starting about 3 or 4 feet from the trunk and 

 extending beyond the spread of the branches. They should be applied before the stored up food in the tree is exhausted, 

 and in my experiments hitherto, July and August were the months chosen. 



In calculating quantities per tree from the number of trees per acre, it will only be necessary to work them out to 

 the nearest lb., or fraction of a lb., not less than J. At least eight or ten trees should be used for each plot, and the necessary 

 number of packets can be made up, containing the manure to be applied to each tree. 



The proportions of the different manures used are for trees in full bearing, and, while the particular quantities best 

 suited to the needs of any particular soil can only be determined by special experiments, the comparative results obtained 

 by adopting a general formula for average soils will indicate the effect of the different combinations on the disease. 



The best relative proportion of each ingredient cannot be definitely stated, but from the well-known effect of nitrogen 

 on this disease, and the singular deficiency of phosphoric acid in our soils, in the complete manure here used, the former 

 is reduced and the latter well supplied. 



In the following experiments to be carried out there are nine variously treated plots, with a check plot on each side 

 acting as a guard, so that there are altogether 10 plots, and, if 8 trees are allowed for each, the total is 152 trees. Of course 

 if such a block cannot be found fulfilling all the requirements, then as many plots as possible should be tried. Special 

 manures, such as sulphate of iron, could be tested separately. 



II. PRUNING. 



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

 effects of severe pruning, light pruning, and no pruning at all on this disease. 



A variety in full bearing and liable to Bitter Pit should be chosen, and at least ten to twelve trees experimented on 

 for each style of pruning. 



For our purpose, a row of Five Crowns about ten years old was selected and treated as follows on 8th August : — 



1. Severe Pruning. — The head pruned well back, the laterals considerably shortened, and all fruit spurs thinned. 



2. Light Pruning. — Shortening back the leaders, removing unnecessary laterals, and leaving the rem ining laterals 

 untouched. 



3. Leader Pruning. — The leaders and main limbs lightly tipped. 



4. No Pruning. — The entire tree untouched. 



III. — STOCKS. 



The reciprocal influence of stock on scion, as far as this disease is concerned, will be dealt with in an experimental 

 way. The generally used blight-proof stock — Northern Spy — is known to be a variety very liable to Bitter Pit, and, 

 while certain apples grown on other stocks are not free from the disease, still, it will be instructive to test the effect of 

 various stocks on the varieties worked on them. 



Owing to the limited period of the investigation, these experiments cannot be carried very far, but it is believed 

 that, after a couple of seasons of fruit bearing, there is likely to be some evidence of the effect of the particular stock on 

 the development of the disease. It is only from experiments already begun in this direction that immediate results can 

 be expected, and I understand that Mr. Quinn, of South Australia, has some such experiments under way. Mr. Pescott, 

 Principal of the School of Horticulture, Burnley, Victoria, has also begun preparing various stocks for experimental purposes, 

 and he has kindly placed them at my disposal. By utilizing these stocks, some practical results may be obtained bearing 

 on the problem, even within a limited period of time. 



Experiments have now been commenced with the following : — 



1. Stocks grafted and planted. 



2. Stocks budded for planting out next year. 



3. In addition to this, half-a-dozen different stocks have been selected for experiment, and, by working the same, 

 liable varieties on each, it will be seen in course of time how the fruit grown from each is affected. 



The stocks are Northern Spy, Winter Majetin, French Paradise, Duchess d'Oldenburg, Lord Wolseley, Crab or Free 

 Apple stock. On each of these stocks the following four varieties have been cleft-grafted respectively, viz. : — Annie 

 Elizabeth, Cleopatra, Cox's Orange Pippin, and Prince Bismarck, which are chosen on account of their being the worst in 

 the orchard for Bitter Pit. 



