5. Insecticide-impregnated screens used under ‘multi-target method’ for haematophagous fly control in cattle: a proof of concept

Livestock are seasonally subjected to the nuisance of haematophagous flies, such as tabanids and stomoxyine flies. Topical application of insecticides has short term efficacy (a week or so), is expensive, and generates pesticide residues in animal products and environment. Attractive insecticide-impregnated blue fabrics are used for tsetse fly control in Africa; however, they are expensive and were never evaluated for other haematophagous flies. In previous works, we defined specifications of a white and blue screen specifically attracting haematophagous flies, particularly Stomoxys spp. In the present study, an assay was carried out in Kantchanaburi Province, Thailand, with around 30 of such screen prototypes, made of a multilayer polyethylene film incorporated with deltamethrin. Screens (also called 'targets') were deployed in 12 test farms, to evaluate the efficacy of a so-called 'multi-target method' (MTM); four control farms were also enrolled. A Vavoua trap was deployed one day/week in each farm to follow-up the density of insects. In the test-farms, during the 4 months post treatment, the mean density of haematophagous flies was significantly and consistently reduced by 63-73% compared to the control group. Laboratory tests indicated that insecticidal activity of these screen prototypes lasted around 3-4 months. However, in the field, significant reduction of fly densities was observed in all test farms up to 7 months after screen deployment, possibly as a consequence of the early impact of the screens on fly population dynamics. The significant effects obtained in test farms provided evidence for the proof of concept that MTM is effective for on-farm control of haematophagous and common flies. Durability of the screens will be increased in the next prototype generation. This innovative control method will be evaluated more extensively and in other livestock and poultry farms.