Dung Beetle Update

Dr Shaun Forgie and co-founding business partner at Dung Beetle Innovations, Andrew Barber, are dedicated to rebalancing New Zealand’s pastoral farming systems – improving water quality and soil health – through leadership, education, and the establishment of dung beetles as a sustainable farm management practice.   

More than 900 colonies of introduced dung beetles have been released in New Zealand in the past decade – the result of years of visionary research. Dr Forgie is a world specialist in all things dung beetle with a Masters Honours and PhD on the topic - and all because he was convinced New Zealand would benefit from the services provided by dung beetles which were lacking in its livestock pastures. Historically, large grazing animals were introduced to New Zealand without the agents that evolved in their places of origin to process their dung.  

Forgie and Barber breed tunnelling dung beetles, which dig tunnels beneath a fresh dung pat and ‘bulldoze’ the dung underground, making dung balls in which they lay eggs. The beetles have a lot of material to work with. The country has 6.5 million dairy cows, each producing on average 27 kilograms of dung a day. By the time you add in more than 3 million cattle and 27 million sheep that is over 100,000,000 tonnes of dung each year, Forgie estimates.  

Forgie says beetle tunnelling and relocating manure beneath the pasture surface can result in many benefits including increased aeration of the soil allowing water to penetrate better. “Dung beetle activity, therefore, leads to reduced run-off of rainfall and better retention of dung and urine in the soil. This, in turn, results in reduced microbial contamination in run-off, less leachate pollution and reduced eutrophication,” he says.  

Tunnelling and dung burial also result in increased forage root growth and biological activity in soils under and adjacent to dung pats. Manure left on the surface is a forage foul and leaves a repugnant zone of grazing avoidance 5x the size of the manure pile.  

As a result, reduced pasture productivity just from avoidance can be substantial. However, if manure is buried within a few days of it landing on the pasture surface, it becomes a sustainable, free goldmine of fertiliser and carbon in the soil. This is extraordinarily important, given New Zealand is one of the biggest losers of topsoil through surface erosion in the OECD.   And given that we are now one of the least productive countries in the OECD, we need all the help we can get to improve soil fertility and pastoral productivity and help get this country back on track, Forgie says.  

Beetles therefore encourage greater pasture productivity. Dung burial by the beetles enhances grass growth through nutrient recycling, and increases the amount of pasture available, improving long-term sustainable productivity.  

Dung beetle activity also reduces reinfection of livestock by parasitic worms. The beetles directly or indirectly kill eggs and young larvae of the parasitic worms. They do this in several ways:  Firstly, the dung pat dries out faster as it is broken up by dung beetles – killing parasite eggs and larvae faster than in dung pats without beetles. Secondly, the processing of dung into brood balls by the adult beetles and direct feeding by dung beetles and their larvae kill parasite eggs and larvae. Thirdly, deep burial of dung reduces vertical migration by parasite larvae back up to the soil surface. As a result, reinfection of the infective stages of these parasites is reduced by at least 76%, thus lessening reliance on drenches.  

Faster burial of dung also reduces the incidence of nuisance flies, Forgie says. “Blowflies associated with sheep flystrike do not breed in animal waste, but females use it as a nutrient resource for maturing eggs. In New Zealand, other nuisance flies such as biting stable flies, house flies, and flesh flies are known to breed in livestock dung. When dung burying beetles and dung breeding flies compete in dung, the beetles win.”  

Forgie says survivorship of fly eggs and larvae is significantly reduced by rapid conversion of the dung resource and mechanical damage during dung manipulation by the beetles. Many laboratory and field experiments confirm significant reductions in the numbers of dung breeding pest flies because of dung beetles, he says. Australia introduced exotic dung beetles mainly to combat the fly problem, and forage foul. Dung breeding fly numbers dropped by 87% and recently the West Australian Government estimated dung beetles contribute $1billion to its economy each year, largely due the direct and knock-on effects of fly control.  

The beetles are also doing the country a service in response to climate change. The burial of animal waste and improved infiltration of urine into upper soils will likely reduce methane, Phosphates and to a lesser extent nitrous oxide, and is therefore likely to decrease the emission of greenhouse gases associated with animal waste, Forgie says.  

While quantification of the influence of dung beetle activity on nitrogen emissions remains to be done, some studies show dung beetle activity creates aerobic conditions, altering microorganism fauna in dung pats, brood balls, and soils to reduce methane production. “And when compared to unburied dung, the speed at which freshly deposited dung is buried by moderate to high numbers of dung beetles is also likely to reduce methane production.”  

Forgie says there’s economic benefit from dung beetle activity through enhanced forage palatability, nutrient recycling, and a reduction in pasture pests.  

Farmers can order beetles through Dung Beetle Innovations. Their facility is based on a 3.2 Ha site in Whenuapai and, says Forgie, currently the world’s largest mass rearing facility for insects. Eight varieties of dung beetles are mass produced at the facility. Forgie says there are different varieties for different seasons and differing annual rainfalls. Commercial packages provide release colonies with four kinds of dung beetle, suitable for all regions in New Zealand for year-round self-sustainable control of manure.  

Customers can order online at www.dungbeetles.co.nz  and complete an order form. The beetle innovations team get in touch with their recommendations, and beetles are sent out when each species is at its peak abundance. New season orders generally start being sent from December and progressively after that as new species emerge up to April.  

See also: 

https://www.ruraldelivery.net.nz/posts/Dung-Beetles-for-Cleaning-Pasture