Abstract Two experiments were conducted to compare control of RWW larvae (Experiment 1) or adults (Experiment 2) among insecticide treatments. Both tests were performed at the California Rice Experiment Station, Biggs, in 1990. Each experiment was a RCBD with 3 replications of 3 insecticide treatments and an untreated control. Treatments were applied to 0.94-m diam circular plots, each bounded by a 0.7-m tall aluminum sheet pushed 3-4 cm into the soil. Plots were established on Stockton adobe clay soil and were water-seeded at a rate of 140 kg/ha on 6 May. Stands were thinned to 50 plants per ring on 22 May. Water depth in the plots was maintained at 10 cm during the experiments. Insecticides were applied by hand-held granule dispenser. Furadan 5G was applied 2 d before seeding plots and lightly incorporated by rake into the soil. UAP 308 2G was applied on 1 Jun (Experiment 2) or 7 Jun (Experiment 1). Plots were infested naturally by RWW adults and by adding 25 field-collected parthenogenic adults per ring on 25 May (Experiment 1) or 1 Jun (Experiment 2). The 2 youngest unfurled leaves on each of 20 plants per plot were examined on 24 and 31 May (Experiment 1) and on 31 May and 4 and 7 June (Experiment 2) for scarring caused by adult RWW feeding. Ten 10-cm diam soil cores per plot (1 plant per core) were removed on 26-28 Jun (1 replication per experiment per day). Soil was washed from the roots and the number of immature RWW (larvae plus pupae) per core was recorded.