Grazed pastures are complex ecosystems, and their functionality depends on interactions between plants, animals, soils, manure, and the people that manage them. Invertebrates in these ecosystems fulfill various ecological roles, such as decomposition, predation, and pollination, that we depend on for the productivity of our land and livestock. Management decisions aimed at controlling one aspect of an ecosystem are likely to affect the other components in complicated ways.
Research led by Postdoctoral Fellow Bryony Sands investigated the interactions between management practices, pests, parasites, beneficial insects, and soil health on Vermont dairy pastures. The team worked with 29 grazing dairy farms across the state to investigate how pest and parasite management strategies are impacting livestock health, insect biodiversity, and soil health. Some of the strategies that farmers used included rotational grazing, conventional pesticides, biological control (natural enemies), and alternative treatments such as essential oils.
The results show that rotational grazing strategies can control internal parasites of cattle without the need for chemical pesticides. Natural enemies such as parasitoid wasps and dung beetles can suppress pest fly populations on pastures. Tunneling dung beetle abundance on pastures was correlated with improved soil health outcomes, and soil health outcomes were higher on pastures that were managed under rotational grazing compared to continuously grazed pastures. Beneficial insect populations were negatively affected by chemical pesticides, and species of dung beetle were impacted differently by various grazing strategies.
The work also included the first dung beetle survey of Vermont, and the team found 20 different species of dung beetle across the state. These ranged from tiny ‘dwelling’ beetles that live and breed in the cow patties, to large, brightly colored ‘tunneling’ dung beetles that dig down into the soil, dragging dung below ground into their tunnels. View all of the species that were found in this fact sheet (PDF).
Dung beetles are highly important for the efficient recycling of manure on pastures, and have been shown to improve soil health through bioturbation and nutrient cycling, as well as reducing the habitat for livestock pests and parasites to breed.
The research was published in Agriculture, Ecosystems, and Environment, and can be access through this link. The results highlight that integrated pest and parasite management (IPM) can improve outcomes for cattle, insect biodiversity, and soil health, but that optimal management strategies will be context dependent.