The effect of ambient temperature fluctuations onCulicoidesbiting midges population dynamics and activity in dairy farms: a longitudinal study

The effect of climatic factors on the presence ofCulicoidesLatreille (Diptera: Ceratopogonidae) was previously studied. Nevertheless, lack of laboratory rearing data hampers species-specific prediction of weather fluctuations effect on population size. To determine fluctuations in population size in the field, we recordedCulicoidesand other Nematocerans in seven Israeli dairy farms over two-years (2011-2012) and analysed the association of their dynamics with fluctuations in ambient temperature and total rainfall. In six farms, the most abundant species wereCulicoides imicolaKieffer andCulicoides schultzei(Enderlein) gp., primarily composed of parous females, and in one farmCulicoides obsoletus(Meigen) gp., mostly nulliparous females, were dominant. While the total number of insects was similar in both years,Culicoidesnumbers were significantly higher in 2012, but appeared later in the season and reached a higher peak. A multi-variable linear regression model demonstrated positive association ofC. imicolaandC. schultzeinumbers with the monthly multi-annual ambient temperature and its specific deviation, but not with monthly rainfall.C. obsoletuspopulations peaked at spring and sharply decreased when temperature exceeded 20 degrees C, and were best modelled by adding quadratic terms. Weather-specific estimation of population size under field conditions may enable to predict outbreaks intensity ofCulicoides-borne viruses.

Automated summary

The study recorded fluctuations in population size of Culicoides and other Nematocerans in seven Israeli dairy farms over two years, finding associations with ambient temperature and rainfall fluctuations. C. imicola and C. schultzei numbers were positively associated with temperature, while C. obsoletus populations peaked in spring and sharply decreased with temperature increase.