THE LETHAL EFFECTS OF CYPERUS-IRIA ON AEDES-AEGYPTI

The sedge Cyperus iria, a common weed in rice, contains large amounts of the insect hormone (10R) juvenile hormone III (JH III). Given its w idespread distribution in Asia and Africa, we examined the possibility that C. iria could be used as a safe, inexpensive, and readily availa ble mosquito larvicide. Plants of varying ages were harvested and leav es tested for lethal effects on larvae of the yellow fever mosquito, A edes aegypti. The median lethal doses (LD(50)s) for frozen leaves from 1- and 2-month-old plants were 267 and 427 mg/100 mi of water, respec tively. Leaves from 1-month-old C. iria contained 193 mu g JH III/g fr esh weight, whereas leaves from 2-month-old plants contained 143 mu g JH III/g fresh weight. Larval sensitivity to the plant differed with a ge; 4-day-old larvae displayed the greatest mortality followed in decr easing sensitivity by larvae 5, 6, 3, and 2 days old. Six Cyperus spec ies (C. albostriatus, C, alternifolius, C. esculentus, C. iria, C. mil iifolius, and C. papyrus) of similar developmental stage were assayed for JH III content. Only C. iria was found to contain significant leve ls of JH III.