Larvicidal efficacy of essential oil of betel leaf ( Piper betle ) on the larvae of the old World screwworm fly, Chrysomya bezziana in vitro

Larvae of Chrysomya bezziana are the commonest cause of wound myiasis in some parts of the world. This obligatory parasite is important in humans and in commercial livestock. Kumarasinghe et al have reported that essential oil of betel leaf (EOBL) is larvicidal to C. megacephala but there are no publications on its effect on C. bezziana . This study was done to evaluate the efficacy of essential oil of betel leaf ( Piper betle ) against the larvae of C. bezziana in vitro . EOBL was prepared at the Industrial Technology Institute Colombo, Sri Lanka, according to a standard protocol. The experiment on larvae was carried out at the Research Institute for Veterinary Sciences in Bogor, Indonesia. EOBL concentrations of 2%, 3% and 4% were prepared with Tween 80. Two ml of 4%, 3% and 2% EOBL in 1% Tween 80 (v/v/aq) were poured into separate Petri dishes. Ten 1st and 2nd instar larvae were placed in each Petri dish. Asuntol (Chaumaphos) 1% was used as positive control and distilled water with 1% tween 80 was the negative control. Larval mortality was assessed half-hourly. The experiment was repeated five times and averages were compared. Sustained immobility of the larvae, after exposure to the relevant substances was considered as death. The efficacy of EOBL depended on, the stages of C. bezziana larvae and the concentration. With 4% EOBL, all first instar larvae were killed within two hours and the second instar larvae were killed by four hours. The positive control showed no mortality until four hours but all larvae were weak, from the first 30 minutes. In the negative control, larvae were mobile and active. EOBL 3% killed all the first instar larvae by 150 minutes and 74% of the second instar at four hours. By 210 minutes, 2% preparation had killed 100% of the first instars. EOBL is an effective larvicidal for C. bezziana first and second instar larvae in vitro . This natural product has a great potential to be developed as a novel larvicide against this parasite.