Evaluation of semiochemical toxicity to houseflies and stable flies (Diptera: Muscidae)

Abstract

The housefly, Musca domestica L., and stable fly, Stomoxys calcitrans (L.) are cosmopolitan pests of both farm and home environments. Houseflies have been shown to be resistant to a variety of insecticides, and new chemistries are slow to emerge on the market. Toxicities of selected semiochemicals with molecular structures indicative of insecticidal activity were determined against adults from an insecticide-susceptible laboratory strain of houseflies. The three most active semiochemicals were also evaluated against recently colonized housefly and stable fly strains. Nineteen semiochemicals classified as aliphatic alcohols, terpenoids, ketones and carboxylic esters showed toxicity to houseflies and stable flies. Rosalva (LC(50) = 25.98 microg cm(-2)) followed by geranyl acetone and citronellol (LC(50) = 49.97 and 50.02 microg cm(-2)) were identified as the most toxic compounds to houseflies. Permethrin was up to 144-fold more toxic than rosalva on the susceptible strain. However, it was only 35-fold more toxic to the insecticide-tolerant field strain. The compounds generated high toxicity to stable flies, with LC(50) values ranging from 16.30 to 40.41 microg cm(-2). Quantification of LC(50) values of rosalva, citronellol and geranyl acetone against susceptible housefly and field-collected housefly and stable fly strains showed that semiochemicals could serve as potent insecticides for fly control programs.