412 



Journal of Agriculture, Victoria. [10 July, 1917. 



This is entirely borne out by our experience in this State during 

 the past few years. Though the abnormally wet spring was primarily 

 responsible for the unusual virulence of the disease in situations suit- 

 able for it, Black Spot has for several years past been on the increase. 

 At Mildura, for example, though there have been no severe visitations 

 for about 20 years, complaints have been received from several growers 

 within the past two or three years, and each season the manifestation 

 has become more alarming. Influence of situation has here been very 

 marked; only in de,pressions and parts of blocks where moisture was 

 abundant has the disease shown up sufficiently to attract attention, and 

 the arrival of normal, hot, dry weather nipped outbreaks in the bud. 

 Nevertheless, the number of scars steadily increased, and in these, a& 



Fig. 9. 

 Magnified cross section through a deep scar, penetrating nearly to 

 the pith, on a ripened cane. Scl, selerotia. Fp. fibre bundles of 

 bark. The blacker portions are tissues disorganized by the fungus; 

 they contain closed cavities, m, in which selerotia are also found. 



Prom the irregular nature of the interior of the scar the need for 

 very thorough swabbing, to reach all exposed selerotia, will be re- 

 alized. After Gouirand and Bergeron. 



will be shown presently, the fungus passes the winter. Centres, or 

 foci, capable of acting as starting points for an invasion, were more 

 plentiful than usual, greatly favouring the spread of the fungus which, 

 but for these numerous starting points, would not have been severely 

 felt in spite of the unusually suitable season. 



That this is so is proved by the fact that at Merbein, a comparatively 

 new settlement, though only a few miles from Mildura, Black Spot 

 was markedly less prevalent last season than at the much older Mildura 

 settlement; at Merbein the disease had not succeeded in establishing 

 itself. Likewise at Nyah, also a new settlement. Black Spot was so 

 little in evidence last spring that few of the newer settlers know the 



