164 Journal of Agriculture, Victoria. [10 March, 1919. 



the trees due to the want of the natural shelter afforded by the foliage 

 to the root areas. 



Preventive Measures and Remedial Treatment. 

 It is becoming generally recognised that the early appearance of 

 black spot is due to the ripe ascospores finding a lodgment on the young 

 leaves and fruit. It is also conceded that the most practicable and 

 effective preventive measure is to plough in the old leaves as soon as 

 they have fallen, and thus obviate the production of the ascospores by 

 the rotting of the leaves in the soil during winter. A cover crop of field 

 peas for green manure sown about the time of plon>>liing in the leaves 

 also assists in suppressing the disease. In seasons favorable to its deve- 

 lopment, the spot begins to appear at the fruit-setting. In order that 

 the soil may not be disturbed just prior to or at this period, the time 

 of sowing should be arranged so as to enable the peas to arrive at the 

 full-bloom stage, and be fit to plough under after the fruit has set. 



Plate 192 — Jonathan leaves showing development, etc. 



The conservation of soil moisture by the maintenance of a fine sur- 

 face, earth mulch, particularly where irrigation is not practised, is essen- 

 tial to the growth of the trees. Mr. H. M. Nicholls, Vegetable Patho- 

 logist, Tasmania, advocates leaving the ground undisturbed from the 

 beginning of October to the middle of November at least, and, in the 

 opinion of the writer, he supports this principle with sound scientific 

 deductions. It should be understood, however, that, while the cooler 

 weather experienced in the island State permits of a cessation of culti- 

 vation, the warmer climatic conditions prevailing on the mainland often 

 necessitate intensive cultural operations at this time. This remark has 

 special reference to orchards <,u light soils, and occupying ex]>osed 

 positions. 



Bordeaux Mixture. 



When as many as possible of the winter spores have been destroyed 

 in the manner described and consistent with the principles involved, the 

 remedial treatment of spraying with fungicides to arrest the develop- 

 ment of germinating spores, which survive the preventive measures, 

 should receive consideration. When the weather is comparatively dry 



