YAM TARO, MALANGA, ETC. 239 



YAM 



Leaf Spot. A leaf spot due to Gloeosporium pestis, 

 Massee, attacks the yams in Fiji, causing numerous 

 black spots on the upper surface of the leaves. It is 

 very severe, and the cause of considerable injury, 

 especially in wet seasons. 



TARO, MALANGA, ETC. 1 



These plants appear to be comparatively free from 

 diseases. Barrett 2 says that "all parts of the yautia 

 excepting the parenchyma of the leaf are filled with a 

 thick juice, which protects the plant against the attacks 

 of insects, fungi, and bacteria. A tuber cut nearly in 

 two transversely was recently received from Central 

 Guatemala, without a trace of decay having spread 

 from the wound, the cells at a distance of 1 millimetre 

 from the cut surface being perfectly healthy upon 

 arrival. The juice undoubtedly has great germicidal 

 power." 



The most important diseases are as follows : 

 Rot. This disease has been reported as severe on 

 the lowland or irrigated taro of Hawaii. T. F. Sedgwick 

 says that " the disease appears to be of two forms, one 

 of which is due to soil conditions and lack of drainage. 

 The other is of a fungus or bacterial nature, and is due 

 in part at least to the planting of diseased bulbs." The 

 disease usually starts when the plants are about two 

 months old, and is most likely to attack plants which 

 are weak from other causes. It starts at the lower 

 end and works upward, causing the root to become 

 hollow or to rot. The upper part of the plant appears 

 stunted, the leaves curled, yellowish, and spotted, and 

 a cross-section shows a blackening of the fibro-vascular 

 bundles. If the disease attacks the plants when very 



1 This plant (Colacaisa esculenta, Schott) is also known as cocoes, tayas, 

 yautia, tanias, tanniers, and eddoes. 



2 Barrett, O. W., Porto Rico, Agri. Exp. t Station, BuL 6 (1905). 



