224 



PLANT SANITATION. 



Mycological Notes. 



By T. Petch. 

 (Illustrated.) 



THREAD BLIGHT. 



This blight has been known to Indian tea planters for along time, and 

 has done serious injury in many districts in that country. It is said to be 

 found in the jungle on many trees, in fact, "it is a question to what extent 

 any jungle plant can be considered absolutely free." 



In Ceylon it has grown for several years on nutmeg trees together with 

 Horsehair Blight (Marasmius rotalis), and one instance of its occurrence on tea 

 has been reported. 



It has also been recently observed on cacao in St. Lucia and Trinidad, 

 where the trees are attacked by the same combination of Thread Blight and 

 Horsehair Blight as occurs on the nutmegs at Peradeniya. 



The fungus makes its appearance on branches and stems as a white thread 

 which is somewhat woolly and adheres closely to the stem. It branches over 

 the stem in various directions, but chiefly upwards, and spreads over all the 

 smaller twigs. When it reaches a leaf it spreads over the lower surface in a 

 series of veins, each with a thinner fiat border. In India it is said to cover 

 the whole under surface with a white felted layer ; I have not observed this in 

 Ceylon. Where two leaves touch one another it spreads from one to the oth er 

 forming a thickened cushion at the point of contact. The leaves then turn 

 brown and die, but instead of falling to the ground, they remain attached to 

 one another and to the stem by the fungus threads so that a tuft of decayed 

 leaves is suspended from the branch. 



The above refers to its effect on nutmeg, and on tea in India. It has 

 not yet been seen on the leaves of tea in Ceylon. 



Watt and Mann state that wherever the threads go, there is an internal 

 mycelium just under the bark, and the branches are ultimately killed by the 

 choking of the vessels in the exterior of the "cambium zone" by the mycelium 

 of the fungus. Massee supposes that the mycelium travels underground, and 

 first attacks the root, afterwards passing up the stem either externally or 

 internally, always finally coming to the surface. Cases of underground infection 

 have been recorded, but experiments in this direction have given negative results. 

 It is difficult to see how such could account for its occurrence at the ends of 

 overhanging nutmeg branches 10 feet from the ground when the tree is in all 

 other parts quite healthy. 



Though at first considered harmless, it is now regarded as a serious blight 

 in the Indian tea districts. In Ceylon where it is unaccountably restricted to 

 the stems of tea bushes, its effect is negligible as far as is known, but, in view 

 of the possibility of its spread to the leaves, it should be carefully looked for 

 and immediately eradicated when found. 



The Indian Thread Blight has been referred to Stilbum nanum, a minute 

 fungus resembling a small pin, which has been found on decaying twigs after 

 they have fallen to the ground. The identification is, however, considered 



