58 BITTER PIT INVESTIGATION. 



E. IRRIGATION EXPERIMENTS. 



Experiments have been conducted in Mr. Cowan's orchard, Bacchus Marsh, since 1911 with Sturmer 

 Pippin. There was no crop on this variety in 1914-15, as a result of drought, heat, and Thrips. In 

 1915-16 there was a very heavy crop, but the fruit was smaller than usual, and not a sign of Pit. 



These experiments were only of a preliminary character, as the conditions were not suitable for 

 extended operations and were merely intended to show the effect on Bitter Pit of applying irrigation 

 water at different seasons of the year. 



The Sturmer Pippin variety of apple was chosen, since it was consistently badly pitted year 

 after year, and one-half of the row was irrigated once, while the other half was irrigated twice. There 

 was nothing very definite in the way of results, except that there was a slight difference in favour of 

 the trees receiving two irrigations, as compared with those receiving only one. 



In isolated cases it was observed that Stunner Pippins, which had been heavily watered at the 

 ripening period, were very badly pitted, and a single Cleopatra tree which was lightly and constantly 

 watered throughout the season bore no pitted fruit. In another part of the orchard Cleopatra trees 

 which had been irrigated only once towards the end of November showed a moderate amount of pitted 

 fruit. 



In the United States of America Professor C. Brooks (3) carried out irrigation experiments in 

 1915, which show very decidedly for one season, that when apple trees are heavily watered, and 

 particularly late in the season, there is a much higher percentage of Pit present than when medium or 

 light watering is applied. The variety chosen was Grimes, five years old, and a susceptible variety at a 

 susceptible age. 



The following table gives the results : 



TABLE XX XIV. 

 PERCENTAGE OF BITTER PIT IN HEAVILY, MEDIUM, AND LIGHTLY WATERED TREES. 



12 Days after After 6 Weeks in 



Irrigation. Picking. Cellar Storage. 



Per cent. Per cent. 



Heavily watered throughout season . . . . . . . . . . 43 73 



Medium supply of water throughout season . . . . . . . . 17 54 



Medium supply of water until 1st August (February in Australia) 



then heavily watered . . . . . . . . . . . . 49 81 



Lightly watered throughout season . . . . . . . . . . 14 40 



It will be observed that when water was applied liberally late in the season there was absolutely 

 the highest percentage of Pit, while the least occurred in those trees lightly watered throughout 

 the season. 



In order to reduce Pit, therefore, where irrigation water is used, it should be applied in such 

 quantities and at such times as to enable the tree to make a steady, as opposed to a spasmodic, growth. 



Excessive watering, especially late in the season, should be avoided, and a uniform supply of 

 water maintained. 



F. COLD STORAGE EXPERIMENT. 



This experiment was continued with apples grown at the Yanco Government Farm under 

 irrigation conditions, as it is considered by many that such apples are more liable to Bitter Pit than 

 those grown with the natural rainfall. The trees are comparatively young, being between seven and 

 eight years old, and the apples were picked on the green side, when they had reached their full size, but 

 not yet perfectly mature. They were wrapped and packed as for export, so that the conditions were 

 exactly similar to those adopted for the oversea market. 



