A comparative laboratory study on population parameters of Spodoptera frugiperda (Smith) (Lep.: Noctuidae) fed on corn (Zea mays L.) and two of the most predominant grasses in Tucuman (Argentina) Guineagrass (Panicum maximum Jacq.) and Bermudagrass (Cynodon dactylon (L.) Pers.) was carried out. The diets used determined changes in diverse parameters such as duration of life cycle, number of larval instars, sex ratio, life expectancy, fertility and/or fecundity. Regarding to the life cycle duration, significant differences among host plants were recorded for the different developmental stages. Females fed on a corn diet showed a fertility of 92.1%, while those breeding on a diet based on Guineagrass showed 96.4% and 99.8% on Bermudagrass. Mean daily egg production ranged within 99.4 (fed on Bermudagrass) and 187.8 (fed on Guineagrass). Total mean egg production also varied with larval diet; maximum value was recorded for females fed on Guineagrass leaves (0 1282.7 ± 38.6 eggs/females). Results suggest that individuals bred on this grasses during final winter could play an important role in FAW population dynamic performance affecting corn crops in Argentina's Norther Region.
