The effects of cultural practices on mosquitoes breeding in the rice fields of 3 agroecosystems in north, central and south Louisiana were determined. Larvae of Anopheles crucians Wiedemann, An. quadrimaculatus Say, Culex erraticus (Dyar and Knab), Cx. salinarius Coquillett, Psorophora columbiae (Dyar and Knab), and Uranotaenia sapphirina (Osten-Sacken) were collected from producing rice fields. Mosquito breeding occurred in the rice fields from the end of May through September although rice planting and initial irrigation occurred approximately 1 month earlier in the southern and middle rice-growing regions than in the northern region of the state. Mosquito breeding increased substantially in the field that was reflooded with irrigation water to produce a second crop of rice. Molinate applied to 2 fields at the registered rate of 6.72 kg Ai/ha, 4.42 ppm in 15.24 cm of rice field floodwater, to control aquatic weeds completely eliminated mosquito breeding for 2-3 weeks. Laboratory data indicated that the LD50 of Molinate to 4th instar Cx. pipiens quinquefasciatus Say larvae was 1.0 ppm and the LD90 was 2.4 ppm. For Ps. columbiae, the LD50 was 1.2 ppm and the LD90 was 3.8 ppm. Early season applications of carbofuran to control the rice water weevil, Lissorhoptrus oryzophilus Kushel, in 3 rice fields aided in preventing mosquito breeding, while late season application of methyl parathion to control the rice stink bug aided in preventing the reestablishment of permanent water species in the field. Late season application of insecticides to crops in adjacent fields could have had a detrimental effect on adult female mosquitoes attempting to utilize the rice field as breeding habitat. The population density of Ps. columbiae increased with the introduction of cattle into the harvested fields, which provided both host animals and hoofprint oviposition sites. Harvest equipment tracks partially filled with rice plant debris provided additional ovipositional sites for Ps. columbiae and Cx. salinarius.