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?
Among their many benefits they can cut nematode reinfection rates by 76% and cut reliance on chemical drenches, he says. His research in New Zealand supports this, as does extensive overseas research, he told a Warkworth seminar the use of dung beetles onfarm.
“Because of what they do ecologically, for us they are the most highly studied of all insects. So if I go on about their benefit it’s not because of hoo-ha…. It’s based on studies done comprehensively all over the world.”
Some drenches will affect dung beetles – slowing them down or even killing them, he told the farmer workshop. “But there are ways around that and establishing dung beetles can knock the heads of the nematodes you are drenching for. Your reliance on chemicals will drop through the floor and you won’t rely so much on that process.” But there are also dung beetle-friendly drenches.
Beetles will fly to wherever they smell fresh dung: smell is the key, he said. They are remarkable at tracking down where fresh dung is. “They will fly to wherever that smell is whether it’s a kilometre or several but [they prefer not] to fly that far because that uses lots of energy.” Rotation should be adjusted to bring fresh dung within range with every rotation, when establishing dung beetles on a property. You can also establish a “fresh dung island” to ensure there’s always a supply.
In answer to a question, Forgie says the ability of dung beetles to use cowshed effluent had not been studied properly but could be part of future study. But if the effluent was laid on pasture dung beetles would consume it. “I have seen liquid dung come out of a cow and as soon as it hits the ground the beetles are flying in.”
Untouched dung can sit on a paddock for four-eight weeks, contributing to compaction which reduces soil health and causes problems of surface runoff.
And production is lost because of forage fouling: the animals do not want to eat around a cowpat – the ‘zone of repugnance’ around a pat, about five times its size. If a cow excretes about 11 times a day and each pat takes four-eight weeks to break down, the cows avoid that area, wasting the productiveness of a lot of land area.
Break feeding may deal with forage avoidance but it is not good for the animals because of increased transmission of nematodes and other pests and disease, Forgie says. Cowpats also eventually reach waterways and contribute to soil degradation. Dung beetles can consume a cowpat in 24-48 hours.
As for farming’s reliance on the $700m chemical drench industry – and chemical dependency because of resistance problems – Forgie says many studies support killing nematodes naturally using dung beetles. “If we take an integrated approach, with drenches used a bit more wisely, and dung beetles and pasture rotation, you’ll break the back of dependency on chemicals.”
Dung beetles will increase levels of plant nutrients because dung is full of phosphates and nitrates. Studies show that the nutrient levels under one cowpat worked on by dung beetles last two years or longer. Their work reduces compaction, brings subsoils to the surface, increases organic matter in soil, cycles nutrients and brings a five-fold increase in earthworms.
They also improve water infiltration into the soil, reducing ponding and helping inputs enter the upper soil level, so reducing the contaminants in the waterways. The studies have shown increases in root biomass, plant height, protein levels in the grass, nitrogen content and grain production.
Forgie referred to his own studies and to significant documentation overseas of up to 76% reductions in reinfection of animals with nematodes because of the action of one species of dung beetle.
An 84-day experiment Forgie did in New Zealand supported the results of overseas studies which showed a significant reduction in nematode third-stage larvae in untreated cowpats using dung beetles as compared to cow pats from animals treated with drenches.
They believe the dung beetles act in three ways that affect nematodes in cowpats: aerating and dessicating the eggs; physically damaging the eggs as the dung is moved; and burying or accidentially eating them. Adults suck up nutrients including eggs, and dung beetle larvae chew them. Dung beetles also bury the dung too deep for the nematodes to survive.
The Environmental Risk Management Authority (now the Environmental Protection Authority) in February 2011 approved the importation and release of 11 species. Risks were rigorously assessed as negligible, Forgie says.
Eleven species of beetles have been brought in to cater for different conditions such as soil and climate. The project has been working with four of those reared at Landcare Research. This is expandable to commercial scale with hundreds of thousands of beetles. Dung beetles supporters are said to include Bruce Wills, Beef + Lamb NZ and Landcorp.
Forgie likens the situation with dung beetles to that of the car industry – resistant to looking at other technologies until public pressure forced the industry to develop electric cars. Farmer pressure will underpin a move to dung beetles and within 50 years they will be on most farms in New Zealand.
He told Dairy News dung beetles are not the only solution to problems facing the dairy industry, but they are one important solution. Significant effects have been shown on nematodes, for example. “It is one of the things that could help you; it is not the overall solution but it is one of the better solutions you could use.”
