Black Spot Experiments, 1903-4. 761 



BLACK SPOT EXPERIMENTS, 1903-4. 



By D. McAlpine. 



From the valuable report on the rainfall of the year 1903 in the 

 May Journal, by Mr, Baracchi, it will be seen what an exceptional 

 season it was, and how unequally the rain was distributed over the 

 several months. For the preceding- seven years, from 1895 to 1902, 

 the drought was more or less general, not only in Australia, but also 

 in India, East and South Afinca, and elsewhere, and in the 

 opinion of the late Director of the Indian Meteorological Department 

 it was parallelled, " so far as we are aware, only by the seven years of 

 famine in Egypt of Biblical history." 



The season, while generally favorable for growth, was particularly 

 suitable for the development of fungus diseases such as black spot, 

 and not only so, but in many instances, the attacks of this fungus 

 were continued unusually late, even till the fruit was almost fully 

 formed. 



Late Development of Spot- 

 In a large number of orchards there was a second infection of the 

 black spot, and the fungus appeared on apples and pears during-^ 

 December and January, although previously quite clean. This sudden 

 appearance, as it seemed to the fruit-grower, was easily accounted for 

 by the unusual weather conditions prevailing at that time — plenty of 

 moisture and thunderstorms between the showers supplying the best 

 possible conditions for the development of the fungus spores lying- 

 latent and ready to burst into activity, whenever the necessary heat 

 and moisture were provided. The soft and succulent nature of the 

 growth also favored the entrance into the tissues of the germ tubes 

 of the fungus, and the result was, where proper spraying at the right 

 season had not destroyed the germinating power of the spores or 

 formed a protective coating to the young growth, that the crop of 

 apples and pears was much reduced and seriously affected. 



While visiting Pakenham district in January of this year, in 

 order to observe the effects of this late development on dilferent 

 varieties, I found how peculiar the weather had been. During 

 December 4"23 inches of rain fell, occurring on 11 days, so that it 

 was both excessive and continuous, and in the first three weeks of 

 January 2'47 inches were recorded, falling on six days. This 

 constant drizzle, with thunderstorms between, gave the fungus a 

 fresh opportunity of which it was not slow to take advantage. These 

 exceptional conditions, combined with the late attack and the 

 susceptible character of the fruit, gave rise to various complications 

 which puzzled even experienced orchardists. Thus, in some apples 

 the bitter pit and black spot appeared together, producing large 

 black depressed blotches which rendered the fruit unsightly. A 

 similar development has taken place in previous years, but it was not 

 so general or so noticeable as the recent one. 



