Scientists at the University of Bristol have been studying how the long-term use of parasite medication in cattle (used either internally or externally) effects the number of dung beetles on farms.
The research paper reveals that the abundance of certain dung beetle species is reduced on farms where the cattle had been treated with different types of pesticides. Even when ingested, the pesticides can pass through the cow and still be active in their dung.
Dung beetles are vital for farms for recycling dung pats, bringing nutrients back into the soil, ensuring that pastures are fertile and minimising disease transmission between cattle.
“Damage to dung beetle populations is therefore concerning, and could result in economic loss for farmers,” says Dr Bryony Sands, lead author of the paper.
“It is now clear that long-term use of these pesticides could cause declines in beetle biodiversity on a large scale,” she says.
As well as finding the overall damage to dung beetle populations on these farms, the research found that different species were affected by the different types of pesticides.
The two types of pesticides used for treating parasites in cattle are macrocyclic lactones (MLs) and synthetic pyrethroids (SPs).
The study found that farms which used SPs were less damaging to dung dwelling beetles (endocoprids) than farms using MLs.
“Although these chemicals do appear to be less damaging, farms that used them still had a smaller proportion of certain dung beetles, which are very important in removing dung from pastures by burying it,” adds Dr Sands.
Both SPs and MLs affected the populations of tunnelling dung beetles (paracoprids).
The residue of pesticides in the cattle dung was found to be potentially lethal for dung beetles approximately 30 years ago by the co-author of the study, Professor Richard Wall.
The new research is the first landscape-scale study on the impact of long-term use of pesticides on dung beetles.
“Team DUMP is delighted that new research is being done on British dung beetle populations and pesticides,” says Sally-Ann Spence, an entomologist, farmer and member of The Dung beetle UK Mapping Project (Team DUMP).
“To date, very little information has been available to farmers as to which pesticides are the best ones to use for managing animal welfare without threatening dung beetles – farmers definitely need both as they want the highest animal welfare standards and they want their dung beetles. We look forward to more research being done in this area.”