[Pilot study to evaluate the efficiency of insecticide-treated mosquito net fences for the protection of horses against nuisance insects in northern Brandenburg].

A fence of black mosquito netting of 100 cm height, pre-treated with 80 mg/m2 of deltamethrin and UV-protected, was used to shelter horses from nuisance and biting insects on pasture in northern Brandenburg. The netting material was attached to the surrounding poles of the existing fences at a height of 15 cm above ground. Three trial groups were selected grazing in spatially separated areas with comparable densities of insect populations. One paddock was completely fenced apart from a wall of 170 cm height and 70 m length. The second pasture had only partial protection with 126 m (13.4%) of fence out of a total perimeter of 942 m. The third pasture served as control. Trap catches outside the fully or partially protected pasture were by at least 60% lower than those recorded for the control pasture. Digital pictures from five different anatomical regions indicated fewer flies on horses kept at the completely or partially protected areas as compared to the control area. The average attack rate in the protected areas amounted to 4.4 and 7.6 flies per horse at the completely or partially protected areas, respectively, as opposed to horses on the control pasture with 172.1 flies. In comparison to the control pasture the horses grazing on the protected areas showed fewer defensive movements, grazing in an undisturbed manner.