Parasitization of rice yellow stem borer, Scirpophaga incertulas (Walker) egg masses.

摘要

The studies were carried out on the egg mass parasitism and composition of egg parasitoids of Scirpophaga incertulas (YSB) revealed that egg parasitoids played an important role in population regulation of YSB by parasitising 95% of the egg masses and preventing the hatching of stem borer eggs. Ninety % of the egg masses were completely parasitised and the parasitoids recorded were Tetrastichus schoenobii, Telenomus dignus and Trichogramma japonicum and 77% of egg masses were parasitised by single genus and Tetrastichus schoenobii was the dominant species parasitising 89% of egg masses followed by Telenomus which parasitised 9% egg masses and 23% egg masses were parasitised by 2 or more of the parasitoids. Out of these, 76% egg masses were by Tetrastichus+Telenomus together, whereas 10.4% egg masses were by Tetrastichus+Trichogramma and only 10% egg masses were by Tetrastichus+Telenomus+Trichogramma and 3% by Teleomus+Trichogramma. T. schoenobii was prevalent during all the months (September to November) but Telenomus and Trichogramma were present in the months of September and October when the temperature was more but their activities were not present as the season advanced (2nd week of November).