Abstract:
The efficacy of a 15% (w/w) mixture of octanoic, nonanoic and decanoic acids in light mineral
oil to repel Culicoides biting midges (Diptera; Ceratopogonidae) was determined in
three replicates of a 4
×
4 Latin square design under South African field conditions. The
fatty acids were applied to
±0.07 m2 polyester meshes with a mesh size 2–3 mm fitted to
220 V 8 W Onderstepoort downdraught light traps. To reduce the relatively strong attraction
of the light trap, the black light tubes in the Onderstepoort trap were replaced with
8 W 23 cm white light tubes. The traps were operating overnight next to cattle. Two traps
treated with the mixture of fatty acids collected 1.7 times fewer midges than two untreated
traps. Although this mixture of fatty acids had shown a repellent effect against a number of
blood-feeding insects this is the first indication that it also has a significant repellent effect
against Culicoides species and especially Culicoides (Avaritia) imicola Kieffer when applied
to polyester mesh.
