The use of garlic (Allium sativa) and lemon peel (Citrus limon) extracts as Culex Pipiens larvacides: Persistence and interaction with an organophosphate resistance mechanism.

There is a growing interest in the use of botanical pesticides to reduce th e use of chemical pesticides and also to avoid problems with insecticide re sistance. We present here data from bioassays on Culex pipiens mosquito lar vae using raw garlic and lemon peel extracts made by simply crushing materi al in water. Both garlic and lemon were toxic to mosquitoes. Garlic was mor e persistent than lemon, with no significant differences in kill between fr esh and approximately 4.5 day old treatments. The addition of food to the b ioassays increased toxicity to both lemon and garlic and represent the situ ation in the field more closely, where food will be available to the larva. A mosquito strain resistant to organophosphate insecticides was significan tly less susceptible to the lemon extract which suggests that using natural extracts as larvacides will not necessarily side-step problems posed by so me existing mechanisms of resistance to synthetic compounds. (C) 1999 Elsev ier Science Ltd. All rights reserved.