18 THE RICE WORM (tYLENCHUS ANGUSTUS) AND ITS CONTROL 



in January-February, climb up above the water. That they can do so is evident 

 from the attacks observed during this period on second growth aman paddy, 

 though in Dacca, one of the chief boro areas, these have not been observed 

 after Januarv. There is even some evidence, as mentioned on p. 7, that 

 January attacks have been seen on boro at Gobindapur. Those that do not 

 leave the water are probably 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 copulation. They can feed for a time on the young inrolled leaves 

 of the shoot bud, but when the leaf tissues mature feeding becomes impossible, 

 as explained in the next section. The attack on the second growth from swamp 

 aman paddy can be readily detected, as the shoots that spring from the old 

 stubble very soon produce dwarf ears, and the worms congregate in and at the 

 base of these and cause in them the same easily recognizable symptoms as in 

 the main crop as it matures. But in the boro plants only the obscure symp- 

 toms of the early attack could be expected, and these are readily overlooked. 

 From February or March on, no further migration would be possible, and the 

 boro plants, though, they may possibly bear desiccated worms in their lower 

 parts, escape the injury to the ears and upper part of the stem that causes 

 such losses in the later crops. They are harvested before the break of the 

 rains would allow of further infection. In the same way, the aus paddy does 

 not become severely attacked until June (the infection probably takes place 

 in May), though worms must be present in the water of the lower-lying tracts 

 from the first flooding of the fields. The aman is doubtless attacked at the 

 same time but the attack escapes notice as the crop is still very immature. 

 Worms have been found in the inrolled leaf buds of aman at the end of July, 

 causing little external signs of disease as compared with what they cause in 

 the ripe aus at the same period or in the aman later on ; and there can be no 

 doubt that the invasion of both crops takes place at about the same time. 

 That the damage to the aman is so much greater than to the aus is probably 

 due to copulation only being possible after the rains break. Multiplication 

 has not time to proceed far before the aus is harvested, but can continue for 

 several months during the maturing of the aman. 



Parasitic life of Tyknchus angustus. 



The rice worm can only feed on certain parts of the plants. To those 

 mentioned in the previous paper,* viz., the young ear, the peduncle, the part 



*." Diseases of Rice," p., 15. 



