358 Agricultural Journal of Victoria. 



First Appearance of Black Spot. 



Some orchardists about to give spraying a trials aud who lia\'e 

 acquainted tliemselves \\\i\\ the composition of Bordeaux mixture, 

 fondly imagine that there is some fixed date which is the best time for 

 spraying ; but if they considered for a moment what they spray for, 

 then they would see that there is no such thing. The main object of 

 spraying, as I take it, is either to prevent the si)ores of the fungus 

 rfrom germinating, or to nip them in the bud, just as they are putting 

 forth their delicate germ-tubes, and seeking to penetrate the young' 

 and growing tissues. The time at which the germination of the spore 

 happens is- largely dependent on the nature of the season, which 

 hastens or retards the development of the fungus, just as it does that 

 of the tree itself. Now, if the seasons were perfectly regular, and the 

 development of fruit trees in different localities uniform, it might be 

 possible to give a definite date, but with the varying seasons and 

 conditions, the most that can be done is to indicate the best time for 

 preventing the development of the fungus. It therefore becomes 

 important for the perfect success of our spraying operations, not only 

 that the Bordeaux mixture is properly prepared, and the ingredients 

 in the right projjortions, but that it is applied at the best time for 

 reaching the fungus before it has penetrated the tissues, and gained a- 

 footing inside the plant. 



Some observations made at Killara on the first appearance of the 

 black spot, in the spring of 1902, will be of interest in this connection. 

 The season there was distinctly unfavourable for the develop- 

 ment of the fungus on apples, owing to a dry period in October. At 

 picking time the disease was almost entirely absent from the leaves of 

 nearly all the trees, sprayed and unsprayed alike, only a fcAv spotted 

 leaves being observed, and these were the last to be formed towards 

 the close of the growing season. This attack most probably occurred 

 after the heavy rains of November and December. 



The black spot of the pear begins its work earlier in the season, 

 since as a rule the pear is some weeks in advance of the apple. 

 Hence the greater chance of moist weather about the blooming and 

 setting time of this fruit doubtless accounts for the greater difficulty 

 in controlling the disease. 



As regards apples, some Ribston Pip])ius were sprayed on 

 23rd September, 1902, when the first buds were bursting-, l)nt some 

 time before any blossoms had fully appeared, and when examined on 

 15th October the ])etals were more than half-fallen, and the fruit 

 mostly set. The black spot was met with on a few leaves enclosing 

 the blossoms, and a photograjih of one of these leaves, natural size, is 

 shown on one of the plates. 



When spraying at Doncaster. on 2nd October, ll»Oo, when the 

 trees were coming into flower, and about five or six days before full 

 bloom, there was abundance of black spot on the young leaves and 

 fruit-stalks. Many clusters of fiowers with not a single blossom 

 expanded bore a plentiful cro]) of black s])<)t on the stalks and calyx. 



