70 BACTERIA IN RELATION TO PLANT DISEASES. 



rather soft. As a rule, also, the immune canes are fibrous and the susceptible ones other- 

 wise. Susceptible canes such as Rappoe, Meera, and Djioenig-Djioenig are very intolerant 

 of wet and cold. Resistant canes such as Black Tanna, Green Tanna, or Malabar, and 

 China withstand cold weather and wet soils very well. 



In dealing with cultivation and its influence on the occurrence and virulence of the gumming dis- 

 ease considerable stress is laid on the question of drainage, it being shown that the disease arises spon- 

 taneously (generally, if not exclusively) on ill-drained areas. This proposition, therefore, gains sup- 

 port from the experience that those canes which can tolerate wet land are not subject to the disease, 

 whilst it especially prevails amongst varieties which are not endowed with this character (Tryon). 



According to Tryon soils, as such, exert no influence on this disease. It is equally 

 prevalent on rocky, stony, stone-free, sandy, and clay lands. Lack of drainage, however, 

 has a marked influence. When not directly traceable to affected sets, the disease is almost 

 always most prevalent in low places or flat wet lands. This was observed by Tryon so 

 often that it seems established beyond reasonable doubt. I may quote a few lines from his 

 report : 



Proceeding again from the Bingera estate proper toward Kolan, patches of affected cane were 

 here and there found, and in every instance their occurrence marked the site of areas of surface depres- 

 sion and the convergence of watersheds, and the presence of a wet soil and subsoil. Again, in almost 

 every other case where the disease was met with, both in the Wide Bay and Burnett districts, it was 

 decidedly more pronounced on flats and hollows and where the ground was wet and undrained, a con- 

 clusion not only founded on extended personal observation on my part, but also agreeing with the 

 general experience of the planters themselves. 



This applies of course only to spontaneous outbreaks, not to infection due to planting 

 diseased canes. 



To recapitulate: Select cuttings only from perfectly sound canes; discard supersensitive 

 varieties; and on soils already much infected plant only very resistant varieties. 



PECUNIARY LOSSES. 



In countries where this disease has gained a foothold it is very destructive. The heavi- 

 est losses have been reported by Cobb and Tryon in Australia, and by Dranert in Brazil. 

 In many cases the crops have been almost entirely destroyed. Cobb said in 1893 that there 

 was scarcely a farm on the Lower Clarence, in New South Wales, where the gumming was 

 not abundant. In 1895, Tryon also regarded it as avery serious disease in Queensland, plots 

 containing scores of acres being rendered valueless. Dranert speaks in similar terms of the 

 Brazilian disease. It had been destructive in Bahia for 6 years. The Argentine disease 

 suspected by me to be this malady is also serious (see page 85). 



According to Mr. Clark, a former cane-inspector of Queensland, thoroughly familiar 

 with the disease as it occurs in Australia, and now an inspector in Fiji, this disease occurs in 

 the Fiji Islands to a serious extent. It has been present some years. At first the planters 

 did not know what it was, but now they are familiar with it and are taking restrictive meas- 

 ures. I have this information through Dr. Cobb, who says another man from Fiji told him 

 the same thing. 



If the disease is identical with Sereh, as the writer suspects, then the losses from it in 

 Java alone are to be reckoned in hundreds of thousands of dollars, Sereh having at one time 

 nearly put an end to the sugar industry of that great island. 



Enough has been said to show that the disease is a dangerous one, and planters should 

 avoid the introduction of canes from affected districts even when they are guaranteed to be 

 sound, lest they inadvertently introduce the disease on some of the canes. It is much easier 

 to keep out this disease, as they are now endeavoring to do in the Sandwich Islands, than 

 to fight it when it has gained a foothold. Planters in Louisiana and in Cuba, Porto Rico, 

 and other West Indian islands should in particular be on guard against its introduction. As 

 Cobb remarks, it is a disease peculiarly liable to be transmitted from one country to another 

 in cane-cuttings. 



