Putting excrement to work
What is less than two centimetres long, loves to work during winter, has a hunger for animal poo and could be handy for grape growers?
Dung beetles provide many ecosystem services: decreasing the amount of pasture smothered by faeces (pasture fouling), increasing pasture growth, nutrient cycling, improving soil structure and killing pests and diseases.
Hence, NZ authorities have allowed the importing of dung beetles, now being mass reared here.
I believe that if we can further establish dung beetles in NZ, possibly in the long term millions of these critters will be chewing and burying dung from pastoral animals, with many benefits.
While dung decomposes naturally, intensive farming means large quantities are dropped, and the nutrients and pathogens move into waterways. Pasture production can also be reduced because of fouling.
However, dung beetles search out the faeces of animals which they use for food and reproduction. Most adult dung beetles make tunnels in soil beneath faeces then lay their eggs there.
Other species make balls of the faeces which they roll away and bury deep in the soil before adding an egg.
As the eggs hatch the grubs feed on the dung so they break it down and eventually turn it into a sawdust-like material that adds to the fertility of the soil structure; and the surface dung goes.
The first intentional introduction of a pastoral dung beetle was in 1956 when the Mexican dung beetle took hold at Whangarei; beetles were introduced into South Kaipara in 1994.
But because dung dropping goes on year-round, one species of dung beetle alone is incapable of achieving suitable control.
Widespread use of dung beetles can help improve soil health, reduce runoff, and increase aeration and water penetration into the soil through beetle tunnels; beetles can reduce urine and liquid dung runoff, and reduce microbial contamination, leachate pollution and eutrophication of waterways.
Beetles also help reduce nitrous oxide emissions as 80% of the nitrogen content of dung ‘flashes off’ (is lost by volatilisation) when dung remains on the pasture surface, versus only 10% when beetles bury dung.
Greater pasture productivity is another benefit, as stock will not graze around dung pats, reducing pasture productivity. Burial of nutritious material by dung beetles enhances grass growth, reducing reliance on fertiliser.
Nuisance flies breed in dung but are beaten to resources by fast-burying dung beetles.
Dung beetles could also reduce infection of animals by parasitic worms because dung burial removes the infective stages of the worms; stock drenching could diminish.
Some concerns have been raised that tunnels in the soil created by dung beetles could lead to more leaching of nutrients and E.coli. NZ research shows this is not so because while beetles create tunnels they pack these with their brood balls, sealing them off.
Dung beetles spread only slowly after introduction and research is under way to find better ways to increase their distribution in pasture.
Plenty of information on dung beetles in NZ appears on https://dungbeetle.org.nz/ and describes research done overseas and more recently here.
• Bala Tikisetty is a sustainable agriculture advisor at Waikato Regional Council, phone 0800 800 401.
