Institute and college, pusa, for 1911-12. 55 



4. Plant disease investigations, (a) Paddy diseases. — 

 Considerable time has been given to the investigation of a 

 disease of inundated paddy, locally known as ufra, in the 

 deltaic districts of Eastern Bengal. The disease is said 

 by the cultivators to have existed for at least a generation, 

 but it appears to have greatly increased in virulence in 

 recent years, and has been under the observation of the 

 Eastern Bengal Department of Agriculture since 1908. It 

 was attributed by different observers to insects, fungi and 

 unsatisfactory soil conditions. A conjoint Entomological 

 and Mycological investigation was undertaken last 

 December, when Mr. Fletcher, Officiating Imperial Ento- 

 mologist, and myself visited Noakhali District. The 

 result was to exclude insects as the direct cause and to 

 throw suspicion on a worm of the Nematode class, always 

 found living on diseased plants. This worm, a Tylenclius, 

 member of a genus whose species are already known to cause 

 several serious diseases of cereals (of which " ear-cockle " 

 ill wheat is perhaps the most familiar), is exceedingly 

 minute, practically invisible to the naked eye; it is found in 

 clusters, often containing many individuals, on the surface 

 of diseased parts. The anterior end is provided with a 

 sharp spine and a sucking apparatus, by which the juice of 

 the living cells of the plant is made use of as nourishment. 

 At least two, probably more, complete life cycles occur in 

 a year and, as the female lays a large number of eggs, in- 

 crease is rapid. On diseased plants the worms are found, in 

 the early stages, occupying small brown patches on the leaves 

 and culm. As the crop approaches maturity larger numbers 

 ol worms occur on the peduncle of the ear and just above 

 the next lower node. At these points the stem is deep 

 brown in colour and shrunken to little more than the thick- 

 ness of a thread. Still later, worms are found within the 

 empty glumes of the lower flowers and the ears generally 

 bear no grain. A frequent condition is the failure of the 

 ear to emerge from its enclosing sheath and to this the name 

 thor (or swollen) ufra is applied, from the swollen appear- 

 ance of the head of the plant. In fucca ufra the ears 



