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Butler (E. J.). The Rice Worm {Tylenchus angustus) and its Control. 



— Memoirs Dept. Agric. India {Agric. Research Institute, Pusa), 

 Bot. Ser,, X, no. 1, January 1919, 37 pp., 4 figs. 



A very serious disease of rice, locally called " ufra," is widely 

 distributed throughout the great rice-growing tract at the head of the 

 Bay of Bengal. It is probable that no other plant disease hitherto 

 observed in India, except the cereal rusts that periodically damage 

 wheat, possesses such potentialities for harm. A map shows roughly 

 the limits of the disease as at present known, but its presence is very 

 difficult to detect, as it occurs while the fields are submerged and 

 is at its earliest stage in the winter crop during the time that boat 

 traffic is possible, while the harvest is over when the ground is dry 

 enough to walk on. This disease was discovered in 1912 to be due 

 to a Nematode, Tylenchus angustus, which has some similarity of 

 habits with T. ribes that causes a serious disease of black currants 

 in England. T. angustus apparently feeds exclusively upon living 

 rice. Under normal conditions the worms are active on the plants 

 from June to November in the southern part of the infested tract 

 and rather later in the northern, reproduction being vigorous and all 

 stages of the worm occurring on the plant. The length of the larval 

 stag^ has not been worked out, nor the rate of reproduction determined 

 but it is undoubtedly high. In swampy ground, where a second 

 growth takes place from the stubble after harvest, this period may 

 be extended to February. In the majority of cases, the host-plant 

 dries up when ripe in late November or early December ; the worms 

 then cease feeding, coil up and pass into a resting condition. The 

 influences of such factors as moisture, temperature and light on the 

 longevity and motility of the worms are discussed. Early studies 

 of T. angustus led to the conclusion that free liquid was necessary to 

 enable it to wander, but it has now been proved that the worms 

 can move slowly for considerable distances in a saturated or very 

 damp atmosphere. 



Observations and experiments have shown that at whatever time 

 rice is sown at Pusa between the beginning of December and the end 

 of March, infestation develops from worms left in the stubble from 

 the previous crop only when the air humidity rises after the rains 

 break in June. When sown early, there is little growth before March 

 or April in Pusa, but the worm is not able to affect appreciably even 

 small plants until the air humidity rises enough to allow it to climb 

 up to the parts above-ground. There is evidently no mherent 

 inability in the worms to attack rice during this period, since infestation 

 has been secured in the laboratory by keeping the plants covered 

 with a bell-jar. It is practically certain that the worms occur in the 

 water of low-lying areas in the eariy months of the year and probably 

 a number of them reach the growing spring paddy and get carried 

 up or climb up above the water during the heavy night-dews of 

 January and February. Those that do not leave the water are prob- 

 ably all dead a month or two after the fields are flooded. While in 

 the water they do not multiply, and after they leave it multiplication, 

 can probably only proceed to a limited extent before the air becomes 

 too dry to allow of pairing. After February or March no further 

 migration of T. angustus is possible and the spring paddy, though 



