20 THE RICE WORM (tYLENCHUS ANGUSTUS) AND ITS CONTROL 



vnth adults within infected leaf buda and around the young ear. The length 

 of the larval stages and the time that elapses from egg to adult has not yet been 

 worked out either for the rice worm or for the allied Tylenchus rihes, so that 

 there is no guide as to the rate of multiplication, but it is undoubtedly great. 

 Some of the inoculation experiments carried out at Pusa since the previous 

 paper may now be described. Some of the earlier failures (I and III) are given 

 as they led to the discovery of the close relation between atmospheric tumidity 

 and infection. 



I. 28-3-' 13, sowed paddy in 6 pots. 12-4-'I3, .seedlings numerous, about 6 inches 



high. Water was kept standing about an inch deep on the surface of the soil, 

 which was puddled clay. Inoculated 2 pots by inserting pieces of infested peduncles 

 and internodes bearing many worms under a leaf sheath. The material used had 

 been desiccated for 5^ months in the laboratory. Inoculated 2 other pots by 

 placing some of the same material in the water at the base of the plants. The 

 remaining pots were kept as controls. During the following month dissected 

 several of the plants in the inoculated pots and found in those inoculated through 

 the water a few worms resembling Tylenchus angustus, some at the base and 

 others within the shoot bud higher up. No ufra symptoms developed and the 

 plants grew to maturity and headed out normally, giving 15 to 20 good ears in 

 each pot in November. The plants were kept on a dry verandah, not covered, 

 and the failure to develop an attack of afra was doubtless due to this. The 

 average of the 8 A.M. relative humidity recorded at Pusa during the two months 

 after inoculation was 82-9 per cent. 



II. 27-5-' 15, sowed paddy in 24 pots. 28-7-' 15, inoculated 12 of these with freshly 



collected (4 days old) aus paddy from Noakhali severely infested with Tylenchus 

 angustus by placing pieces of diseased stems and ears in the water at the base of 

 the plants. 10-8-'15, one of the inoculated pots showed definite symptoms of 

 ufra. 14-9-'15, ufra distinct in 9 of the 12 pots and minor symptoms visible in 

 the other 3. Tylenchus angustus present in quantity on the diseased plants. No 

 symptoms and no worms in the 12 control pots. The plants were kept out of doors, 

 and the success is to be attributed to the monsoon conditions to which they were 

 exposed after inoculation. The average of the 8 a.m. relative humidity recorded 

 at Pusa during the two months after inoculation was 86- 1 per cent. 



III. 30-12-'13, sowed paddy in 4 small pots (about 3x2 inches) and thinned to 1 plant 



each. Kept in incubator at 30°C., lighted through glass door. After about a 

 week (when the seedlings were 2 inches high) inoculated 3 of the pots with motile 

 worms, 2 being done with worms that had been swimming in water for a month, 

 the third with worms freshly taken from a growing plant attacked by ufra. No 

 infection resulted and not a single worm could be f oimd to have ascended 2 of the 

 plants which were dissected a week later. The third (one of those done with free- 

 swimming worms) equally showed no signs of infection but was not dissected. The 

 plants were kept in the incubator, the air inside which was dry except for the 

 small amount of evaporation from the smiace of the pots. Similar results were 

 obtained when germinated seedlings were placed on 7-l-']4 in a glass capsule in 

 the incubator with a few c.c. distilled water to which were added .some 20 or 30 

 motile worms fresh from the diseased plant. Only I worm succeeded in climbing 

 up a short distance up one of the shoots. Other experiments in which adults and 

 eggs were used to inoculate seedlings in 6 of the small pots equally failed. They 

 were kept uncovered, remaining indoors untij the plants were too big for the pots 



