Lagartas de Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) foram criadas em laboratório, alimentadas com folhas de arroz (Oryza sativa) e capim-arroz (Echinocloa sp.) a 25±2 ºC; 70±10% RH e fotofase de 14 h. Maiores diferenças foram observadas quanto à duração da fase larval (22,0 dias em arroz e 18,6 dias em capim-arroz), viabilidade de lagartas (78% em arroz e 83,0% em capim-arroz) e pupas (71,4% em arroz e 87,8% em capim-arroz) bem como na fecundidade (773 e 1017 ovos/fêmea provenientes de lagartas alimentadas em arroz e capim-arroz, respectivamente). Insetos criados em capim-arroz desenvolveram-se mais rapidamente, apresentando maior viabilidade e fecundidade. O capim-arroz foi preferido pelas lagartas de S. frugiperda.

Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) larvae were reared in laboratory on leaves of rice (Oryza sativa) and barnyardgrass (Echinochloa sp.) at 25±2 ºC; 70±10% RH and photofase of 14 h. Differences were observed in duration of larval stage (22.0 d in rice and 18.6 d in barnyardgrass), viability of larvae (78% in rice and 83% in barnyardgrass) and pupae (71.4% in rice and 87.8% in barnyardgrass), as well as adult fecundity (773 and 1017 eggs/female obtained from those fed rice and barnyardgrass, respectively). Insects reared on barnyardgrass showed a faster development, higher viability and fecundity than those reared on rice. Barnyardgrass was greatly prefered by S. frugiperda larvae than rice.

A new methodology to evaluate the effect of insecticides on Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) in flooded rice (Oryza saliva) was tested. Artificial infestations with fall armyworm larvae (3rd -4th instars) on rice field plots, fenced by metallic cages was used. Larval mortality was evaluated 48 hours after insecticide application by flooding the rice field and counting the floating surviving insects. Lambdacyalothrin CE (7.5 g/ha) and permethrin CE (25 g/ha) provided high larval control (> 95 %). Cifluthrin CE (7.5 g/ha) and deltamethrin CE (2.0 and 2.5 g/ha) caused less mortality (< 70%). The advantages of this new methodology are discussed.