A fly in the ointment: evaluation of traditional use of plants to repel and kill blowfly larvae in fermented fish.
BACKGROUND
In rural areas in Laos, fly larvae infestations are common in fermenting fish. Blowflies (Chrysomya megacephala, Diptera: Calliphoridae) are attracted to oviposit (and/or larviposit) onto fermenting fish which results in infestations with fly larvae. Knowledge of traditional use of plants to repel larvae during the production of fermented fish is common and widespread in Lao PDR.


OBJECTIVE
How effective are the most salient species in repelling, and killing fly larvae in fermenting fish?


METHODS
The three plant species most frequently reported to repel fly larvae during an ethnobotanical survey throughout Lao PDR were tested for repellence and larvicidal activity of fly larvae infesting fermented fish. The lethality and repellence of Tadehagi triquetrum (L.) H. Ohashi (Fabaceae), Uraria crinita (L.) Desv. ex DC. (Fabaceae) and Bambusa multiplex (Lour.) Raeusch. ex Schult. & Schult. f. (Poaceae) were tested in an experimental design using fermenting fish in Vientiane, Lao PDR.


RESULTS
The repellent effect of fresh material of T. triquetrum and U. crinita, and the larvicidal effect of fresh B. multiplex, is significantly more effective than that of dried material of the same species, and the total effect (repellence and larvicidal effect combined) for each of the three species was significantly more effective for fresh than for dry material. Fresh material of T. triquetrum, U. crinita, or B. multiplex added on top of the fermenting fish repelled 50%, 54%, 37%, and killed 22%, 28%, and 40% of fly larvae. The total effect was not significantly different per species at 72%, 82%, and 77%, respectively.


CONCLUSIONS
The three most salient species are effective in repelling and killing fly larvae in the production of fermented fish, and may be essential to augment food safety during traditional fermentation in open jars.
Department of Systematic Biology, Evolutionary Biology Centre, Uppsala University, Uppsala, Sweden.
Hugo J de
HJ
Boer
Chanda
C
Vongsombath
Jos
J
Käfer
D000818:Animals; D004175:Diptera / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D005260:Female; D005285:Fermentation; D005399:Fishes; D057141:Food, Preserved; D007302:Insect Repellents / Q000494:pharmacology*; D007306:Insecticides; D007814:Larva / Q000187:drug effects; D019684:Magnoliopsida / Q000737:chemistry*; D010936:Plant Extracts / Q000494:pharmacology*; D013045:Species Specificity
D007302:Insect Repellents; D007306:Insecticides; D010936:Plant Extracts