Abstract: Two ben1.oylphenyl urcas (diflubenzuron and triflumufon) were evaluated at different rates and times of application in a 3 year field study to detennine effectiveness in controlling natural populations of the nce water weevil, Lissorhoptnls ol)'Zophilus Kuschel. Application timing was based on the number of days beyond ca. 50% mean rice emergence from the water surface in a continuously flooded field (ca. 10 em depth). The chemicals were applied as single applications at 4, 5. and 7 days and as double applications at. 4 and 10 days, and 7 and 14 days post rice emergence respectively. Three ratcs were tested: 0.14, 0.28, and 0.42 kg (AI)/ha. Both compounds caused significant redudion in immature weevil populations when applied Ill. 0.28 kg (AIl/ha, 4 to 5 days following rice emergence in a continuously nooded field,