The influence of carbon dioxide on the numbers of Culicoides midges collected with suction light traps in South Africa

To implement risk management against diseases transmitted by Culicoides species Latreille, 1809 (Diptera: Ceratopogonidae) it will be essential to identify all potential vectors. Light traps are the most commonly used tool for the collection of Culicoides midges. Taking into account the indiscriminative artificial attraction of light, these traps will collect all night flying insects and not only livestock associated Culicoides midges. Factors that could increase the efficacy of these traps for especially livestock associated Culicoides midges need to be investigated. In the present study, results obtained with CDCand Onderstepoort light traps baited with CO2 were compared to those of unbaited traps. Comparisons were done in two replicates of a 4 x 4 randomized Latin square design. With both traps, the mean numbers of Culicoides midges collected in 16 baited collections were higher than those in 16 un-baited collections. Despite exceptionally low numbers collected with the CDC traps, the increase in the numbers and frequency of collection of Culicoides imicola Kieffer, 1913 was more pronounced in the CDC compared to that in the Onderstepoort trap. These results indicate that the addition of CO2 could increase the efficiency of these traps for the collection of C. imicola, and other livestock associated Culicoides species.