464 Agricultural Journal of Victoria. 



EARLY BLIGHT OF THE POTATO. 



{Alternaria solani (E. &> M:) Jones &> Grout.) 



By D. McAljpine. 



Nature and Symptoms of the Disease. 



Potatoes are subject to a number of diseases, but fortunately the 

 potato disease which is so destructive in other countries has not been 

 found in Australia. This disease, which affects all parts of the plant, 

 leaf, stem, and tubers, is often known as the Late Blight, because it 

 does not usually appear until comparatively late in the season. 



But there is another known as the Early Blight, on account of its 

 appearing just when the tubers begin to form, or even earlier, if the 

 conditions are unfavourable to healthy growth, and it only occurs 

 upon the leaves and stems, not causing the ])otatoes to rot as in the 

 other. 



It first came under my ncjtice in April, 18*J(J, at Leongatha, and 

 since then at other parts of South Gippsland; but although not 

 very generally observed as yet, this is probably owing to its being 

 unrecognized. The accompanying reproductions of photographs will 

 enable any potato-grower to make sure of its presence and thus to 

 take action in getting rid of it. This disease causes serious loss in 

 the United States, where it was first definitely determined in 1891, 

 and it is widely distributed in Europe, as well as in New Zealand, and 

 has recently been discovered in India, where, however, only a few 

 fields were found affected. There is no mistaking this disease when 

 fully developed, although it might possibly be confounded with early 

 maturity and thus escape notice. The stems are hard and woody and 

 of an unhealthy hue, while the leaves are brown and withered, some- 

 what of the colour of tobacco. Owing to this the entire plant finally 

 withers and dies before its proper season, thus causing the tubers to 

 be small, only one-half or one-third their usual size. The tubers, 

 however, are sound, although undersized and immature, and the 

 fungus evidently has no direct affect upon them, as is the case with 

 the Late Blight. 



While closely investigating the disease at Leongatha I found that 

 every kind of potato was affected, whether grown in virgin land or 

 not, and irrespective of being ^rown in any of the three classes of 

 soil found in the district — chocolate, grey loam or black loam, the 

 latter being situated near the creeks and rivers. The average rainfall 

 is about 40 inches, so that there is abundance of moisture, and it was 

 noticeable that the diseased plants produced no fruit, or plums as 

 they are called. When the disease is followed from its earliest stages 

 it is found that the leaves have dark-brown, well-defined, rather 

 irregular spots, which increase in number and size until they overrun 

 the entire leaf and destroy it. (Figs. 1 and 2). If the irregular spots 



