AgResearch develops unique biopesticide

AgResearch scientists are working on a chemical-free biopesticide that kills the pasture-munching caterpillars that emerge in huge numbers in spring and summer. It also kills the notoriously damaging grass grub and a major apple orchard pest, the bronze beetle.

The biopesticide is a naturally-occurring bacterium, Yersinia entomophaga (or Ye). It was discovered in a grass grub corpse during a search for alternatives to chemical pesticides such as organophosphates, which are being phased out.

When eaten by pest insects, Ye releases toxins that "burst open the gut" and cause rapid death, says Dr Mark Hurst of AgResearch's Innovative Farm Systems group, who led the research team.

"The bacterium is very good at killing a large variety of insects, especially beetles and moths. It doesn't, however, harm earthworms, honeybees or other beneficial organisms that we've checked," says Dr Hurst. "Plus it does not persist in soil, which is important for any control agent if it is to be clean and green."

A common worry with pesticides is target pests will develop resistance. This happens with the biopesticide Bt (Bacillus thuringiensis). However, because Ye uses different methods to kill insects, Dr Hurst believes it is unlikely that insects could become resistant.

A novel biopesticide product based on Ye is being explored with industry partner Ballance Agri-Nutrients, with the cooperative providing investment and offering some commercial disciplines to the development process.

"The project is linked with our Primary Growth Partnership research in terms of looking at biological tools that improve on-farm productivity and sustainability," says Ballance research and development manager, Warwick Catto.
"While it's early stage research, there's no doubt the development of new biologically-based solutions for pasture pest control has considerable economic and production potential."

Ongoing research is yielding detailed knowledge of Ye and how it interacts with target insects, some of which was published in prestigious international journals in the past year. Last December a Proceedings of the National Academy of Sciences paper described the structure of Ye's toxic weaponry, which is the only toxin of its kind known to include enzymes that dissolve insects' skeletal structure. In July a paper in Applied and Environmental Microbiology described how Ye disintegrates the insect gut.

Dr Hurst says such knowledge will improve the effectiveness of a Ye-based commercial product and allow tailor-made formulations. It is also vital to the product gaining registration as a pesticide with New Zealand's food safety and environmental protection regulators, a process that is underway and generally takes several years.
Ye also kills other globally problematic crop pests including the diamondback moth, white butterfly, Japanese beetle and locusts.

Biopesticides such as Ye are being developed by AgResearch to help New Zealand producers meet increasing international demand for products such meat, dairy and fruit with no pesticide residue. They are also expected to improve productivity and reduce the environmental footprint of pastoral farming.

Research into Ye has been funded by the Ministry of Business, Innovation and Employment, and two Ministry for Primary Industries programmes, the Primary Growth Partnership Fund, through which Ballance Agri Nutrients has invested in it, and the Sustainable Farming Fund.

Other scientists involved with this research are from AgResearch's Innovative Farm Systems group, Plant & Food Research and the Universities of Auckland and Queensland.