The acute toxicity tests were carried out on fourth instar Cnaphalocrocis medinalis (Guene) larvae from Tamil Nadu Agricultural University culture and field collected population from different parts of Tamil Nadu with monocrotophos, quinalphos, chlorpyriphos and phosphamidon by topical assay and tentative discriminating dose screen was calculated. The insecticide resistance in C. medinalis population was below 25 per rent.
Insecticide resistance, Cnaphalocrocis medinalis, discriminating doseo
