INTRODUCTION. 



INTRODUCTION. 



The investigation has now reached a stage where much that was formerly obscure is now cleared 

 up, and where the conditions under which the disease occurs are so well known as to suggest measures 

 for directing and controlling them. 



Owing to the exceptionally dry season of 1914-15, many of the experiments were barren of results. 

 But where the apple crop was a failure during that season, as in the pruning experiments at Decpdenc, 

 the manurial experiments at Box Hill, and the experiments generally at Blackwood, the succeeding 

 crop promised remarkably well and turned out the best of the whole series. Hence it became necessary 

 to continue the experiments, since they form the basis from which practical conclusions are drawn, 

 and to allow for the variations of the seasons, which often interfere with the continuity of the work. 



It has already been pointed out that everything which concerns the life of the tree has a possible 

 bearing upon Bitter Pit. But we have to select those factors which are most important for our pur- 

 pose and which promise the most immediate practical results. I have therefore paid special attention 

 to pruning in an experimental way, since it can divert the nourishment into proper channels, and 

 distribute it where most wanted, so that the fruit is well and evenly developed and less liable to those 

 fluctuations which encourage Bitter Pit. The blossom- or fruit-buds are also specially studied, since 

 they are the foundation of fruit bearing, and on them depend the quality and the quantity of the fruit. 

 The past season with its prolific crop and generally under-sized fruit where irrigation had not been 

 practised, might have been expected to offer the most favourable conditions for resisting the disease. 

 But Bitter Pit has been very prevalent in some districts notwithstanding. The dry conditions which 

 prevailed during the late spring and early summer, which is the critical season for the proper growth 

 of the apple, followed in Victoria by the heavy rains in February, supplied those conditions which 

 are most favourable to the development of Pit, especially where the trees were heavily pruned. The 

 sudden change from dry to wet conditions induced an abnormal flow of sap, and the over-pressure 

 exerted in the conducting vessels of the fruit and the adjoining pulp-cells, brought about a rupture 

 and collapse in the latter, the well-known symptoms of Bitter Pit. 



The bio-chemical researches on Bitter Pit have not been continued, owing to the lamented death 

 of Dr. Rothera, which occurred in August of last year. He rendered me valuable assistance in the 

 investigation, as may be seen from his last contribution in Report IV. He had intended following 

 up various lines of investigation, particularly the early detection of Pit by micro-chemical methods, 

 before the browning stage has been reached. By the death of Dr. Rothera, bio-chemical science has 

 lost one of its most promising workers, and I have been deprived of the wise counsel and co-operation 

 of a highly esteemed colleague. 



In a recent review of my previous Reports in Phytopathology, the official organ of the American 

 Phytopathological Society, it is stated that : "The series of publications furnished by far the most 

 elaborate treatment ever given this subject, and is probably the most voluminous report that has ever 

 been made upon any single plant disease." 



As a justification for this exhaustive treatment, I have pointed out from the very inception of 

 this investigation, that it involves not merely the fruit, which is the final outcome of all the vital 

 activities of the tree, but the conditions and results of the functional activity of every organ, at least 

 during the fruit-bearing stage. It therefore concerns itself with the proper action of the roots in supply- 

 ing the necessary nutriment from the soil, with the conducting tissues of the stem in conveying the 



