Natural insecticide to fight black beetle closer to fruition

Research into the product, that is infused with the naturally occurring bacteria Yersinia entomophaga (Ye), will soon begin its second stage which includes investigating the optimum application rate and production scale-up.

AgResearch senior scientist Dr Mark Hurst says that if successful the product would have a significant impact on black beetle populations which cannot be effectively controlled by insecticides in established pasture. 

It’s a great example of an effective biopesticide, AgResearch says: a natural pesticide based on micro-organisms or their bioactives, targeted and safe for the environment and humans and helping to solve many insect pest and disease problems. 

Black beetle (Heteronychus arator) is found in warm areas of the North Island, where root feeding larvae are capable of severe pasture damage. Dry summers and autumns for three years have contributed to a population explosion.

The product is based on the Ye bacterium discovered in 1996 in a grass grub corpse during a search for alternatives to chemical pesticides such as organophosphates, which are being phased out. Ye releases toxins that ‘burst open the gut’ of the insect and cause rapid death, says Hurst, who led the research team.

“The biopesticide is good at killing a large variety of insects, especially beetles and moths. But it doesn’t harm earthworms, honeybees or other beneficial organisms.”

Senior scientist Michael Wilson says trials carried out in autumn and spring last year gave encouraging results and suggested that spring might be the optimum time to utilise the product.

“In spring you kill the adults before they lay eggs so you get fewer larvae hatching and it’s actually the larvae that do most of the damage. It’s difficult to target larvae directly with a biopesticide because they are underground, so hitting the adults in spring is probably the way to go.”

Hurst says that now the product has been proven to work, they will explore the best methods for manufacture and application in existing farm machinery.

Meanwhile, entomologist Sarah Mansfield is investigating the movement and feeding behaviour of black beetles for the most effective delivery technique for the product.

Research into biopesticides is ongoing in the Next Generation Biopesticides Programme (NGBP), an initiative of AgResearch, the Bio-Protection Research Centre (Lincoln University) and Plant and Food Research. 

NGBP leader Dr Maureen O’Callaghan says all the research points to a user-friendly biopesticide product being much closer. “The very promising results achieved in the field trials are the result of excellent collaboration between researchers, industry partners and farmers.”

Development of the product has been supported by Ballance Agri-Nutrients and MPI via their PGP programme, and DairyNZ.

Waikato farmers have hosted field trials as part of several Sustainable Farming Fund projects focussed on controlling pests, O’Callaghan says.

The biopesticide product can be used with other techniques to control black beetle., such as sowing insecticide-coated seed to kill black beetle adults when the grass is germinating.

Farmers can also use ryegrass cultivars containing the endophyte AR37.