1 Jury, 1899.] QUEENSLAND AGRICULTURAL JOURNAL. 57 
Plant Pathology. 
POTATO DISEASE. 
By HENRY TRYON, 
Government Entomologist. 
The following popular account relating to the nature and treatment of a special potato 
affection occurring in the portion of the Moreton Bay district mentioned having been regarded 
as possibly having an interest for others besides those resident therein, in response to whose 
representations it was prepared, has been accordingly submitted by the Department for inclusion 
in the Journal. It has, however, been prefaced by an excerpt, descriptive of symptoms, from the 
earlier Report (1894), alluded to in order to render it suitable for this further purpose :— 
INTRODUCTORY, 
Tue potato affection brought under notice of the Department as occurring 
in the Gramzow and Alberton district of Beenleigh is identical with the new 
disease of this plant whose nature and cause were first made known by the 
writer in May, 1894, in a “ Preliminary Report on a New Potato Disease 
prevalent in Southern Queensland,” and that has been designated, in this 
colony, ‘‘Tryon’s Potato Disease,” and elsewhere “A Bacterial Disease of the 
Tomato, Egg-plant, and Irish Potato” (Brwin F. Smith). 
This disease was probably brought into the Beenleigh district some years 
since in seed-potatoes. Its existence therein was apparently at first a matter of 
no comment; but of recent years it has become of more and more general 
occurrence, until now, to quote Mr. I. W. Peek, “it is very prevalent . . 5 
the English varieties are greatly affected in the Alberton and Gramzow district, 
and slightly so in the Waterford district,” and is inflicting very serious damage. 
Prior to its discovery in Queensland in May, 1894, it existed—as there are 
good grounds for concluding—unrecognised both in the mother colony of New 
South Wales and in the United States of America. With regard to the latter 
territory, it has since the above event been positively identified, by comparison 
with the details of a comprehensive technical description prepared as the 
outcome of patient research by Dr. Erwin F. Smith, of the U.S. Department of 
Agriculture, and published in August, 1896, with a potato affection that had 
long occurred there greatly to the detriment of the potato-growing industry, but 
whose nature had not then been definitely ascertained. ; 
SYMPTOMS. 
[The following are the characteristic features presented by the plant when 
diseased :—When the potato-plant is in process of vigorous growth, and exhibits 
every evidence of health, it suddenly commences to droop as if lacking moisture; 
it becomes after a few hours generally flaccid, its branches bend downwards, © 
and its leaves have their edges turned inwards so as to expose their under- 
surfaces. These events happen in a few hours, without any premonitory 
symptom whatsoever. The plant thus smitten never revives, but gradually — 
succumbs, the lower foilage eventually withering and becoming discoloured. 
On examining the roots and tubers of a plant thus recently affected, it will 
be found that these are to all appearances perfectly sound. An attentive 
observer may, however, notice that the faint line—henceforth referred to as the 
‘ying’—which is seen on section of a healthy tuber at a short distance within’ 
and parallel to the surface, is more evident than usual from having become 
slightly translucent or even somewhat darkened in colour. At a later period 
an opaque, white, thick, tenacious fluid exudes in minute quantity from some of 
the eyes of the tuber; and it is this that, when the potato is removed from the 
soil and its surface permitted to dry, causes the earth to strongly adhere at 
these points, leaving behind—on being detached—a glossy film. If kept 
perfectly dry the tuber usually undergoes no destructive changes, but when 
remaining in the soil, or surrounded by a damp atmosphere, such supervene. 
The exudation from the eyes now becomes more copious, and, as judged by the 
presence of froth, issues with effervescence ; the skin in their vicinity assumes 
