The efficacy of sustained release Altosid sand granules to control adult Aedes taeniorhynchus and Culex quinquefasciatus emergence was investigated. Sand granules applied at a 7-day preflood application rate of 5.6 kg/ha controlled 99% of the Ae. taeniorhynchus emergence in saltwater plots for 44 days posttreatment and 35% of Cx. quinquefasciatus in freshwater plots. A 5.6 kg/ha rate controlled 100% of the Ae. taeniorhynchus emergence for 30 days posttreatment in semi-permanent saltwater plots. Altosid pellets were used at the label rate for comparison. Sand granules applied at 11.2, 16.8 and 22.4 kg/ha against Cx. quinquefasciatus in freshwater plots gave 98% emergence inhibition at the 22.4 kg/ha rate 37 days posttreatment, 93% at 16.8 kg/ha for 22 days, and 100% at 11.2 kg/ha rate for 16 days.