40 WSPs: convenient, pre-measured 1 pouch / 50 sq. feet Dionne Larvae Halt II is an ideal larvicide to control disease carrying mosquitoes, before they become mosquitoes! Dionne Larvae Halt II is for the control of mosquito larvae living in organically polluted waters such as storm drains, catch basins, ditches, estuaries, salt marshes, mangroves, seepage ponds, lakes, ponds, rivers, dormant rice fields, sewage lagoons.