Abundance of the tick Dermacentor reticulatus in an ecosystem of abandoned meadows: Experimental intervention and the critical importance of mowing.

The effect of agricultural activities on the environment has been falling in many areas of Europe in recent years and the associated abandonment of crop fields, meadows and pastures may enable an increase in tick densities. In the present study we assessed whether regular mowing would have a negative effect on Dermacentor reticulatus populations and whether the cessation of regular mowing would cause an increase in abundance of D. reticulatus ticks. Two field experiments were conducted during a five-year period (2012-2016) in the Mazowieckie (Mazovia) region of Central Poland. Experiment 1: The long-term effect of mowing on tick population was tested in the meadow ecosystem of Stoski, an old fallow land plot that was mowed three times a year. Experiment 2: Neglecting the cultivation by abandonment of arable land was evaluated in Kury village. Four areas (2 experimental 'fallow lands', 2 control meadows) were selected. The first fallow land plot was a fenced off area comprising mostly of a horse pasture and the second fallow land plot was designated in an old abandoned orchard. At each site, ticks were collected in consecutive springs and autumns by dragging at least twice during each season from experimental and control areas. Altogether 1452 D. reticulatus ticks were collected and their densities were compared by multifactorial ANOVA. In the end of the first experiment, a significant decrease (6 times) in tick abundance was observed in the mowed area in comparison to old fallow land. In the end of the second experiment, tick abundance was three times higher in the experimental fallow lands in comparison to the control meadows. In conclusion it was found that regular mowing significantly reduced the density of questing D. reticulatus ticks in open areas. Cessation of mowing may enhance the number of ticks and the associated risk of acquiring tick-borne diseases.