In a field experiment in 1988-91 at Bijapur, Karnataka, sunflowers cv. Morden was defoliated by 0, 25, 50, 75 or 100% on 25, 50 or 75 days after sowing (DAS) to simulate attack by Spilosoma obliqua [Spilarctia obliqua] and Plusia orichalcea [Thysanoplusia orichalcea]. Mean seed yield was reduced by 14.78, 28.21 and 15.67% when the plants were defoliated on 25, 50 or 75 DAS, respectively. Defoliations of 25, 50, 75 or 100% decreased seed yields by 6,57, 15.67, 27.16 and 58.06%, respectively.