Field Evaluation of Egg Parasitoids, Trichogramma japonicum Ashmead and Trichogramma chilonis Ishii, against Rice Yellow Stem Borer and Leaf Folder
Field evaluation of two egg parasitoids, Trichogramma japonicum Ashmead against rice stem borer, Scirpophaga incertulas (Walker), and Trichogramma chilonis Ishii against leaf folder, Cnaphalocrocis medinalis (Guenee), was carried out in farmers' fields in three locations at Karakkad village, Palakkad district, Kerala, during three seasons in 2003 and 2004 in comparison with insecticide application. Release of T. japonicum @ 100000/ha followed by application of azadirachtin 1 per cent against yellow stem borer reduced dead hearts from 12.21 to 91.02 per cent and from 27.4 to 58.2 per cent over insecticide application during kharif and rabi seasons, respectively. Incidence of white ears was reduced by 72.41 to 92.86 per cent. T. chilonis reduced leaf folder damage by 41.68-98.60 per cent over conventional insecticide application. Release of egg parasitoids in rice resulted in an increase of yield by 25.79-45.13 per cent over insecticide treated plots, with a mean cost-benefit ratio of 1:2.6 and 1:1.9 in parasitoid released and insecticide applied plots, respectively.
Cnaphulacrocis medinalis, Rice, Scirpophaga incertulas, Trichogramma chilonis, Trichogramma japonicum.
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