A bioassay for natural insect repellents

A practical bioassay for natural product insect repellents was developed and validated. The Asian tiger mosquito ( Aedes albopictus) was used in this study. Djulis ( Chenopodium spp.), an indigenous plant from Taiwan, provided better insect repellency than neem tree ( Azadirachta indica) oil, a well-known insect repellent. The % repellency of each test material was converted to 50% effective dosage (ED 50) by probit analysis for better comparison between test materials. The ED 50 for insect repellency in descending order was djulis leave extract (0.532%), neem oil (0.579%); djulis seed extract (0.930%) and sea lily ( Crinoid spp.) (1.022%).