Biopesticides at AgResearch

Biopesticides at AgResearch

The New Zealand pastoral sector is suffering losses caused by endemic pests such as grass grub, manuka beetle, porina, plantain moth and invasive species such as black beetle. Damage caused by these pests is increasing in response to intensification of farming and climate change. Relying on conventional, broad-acting pesticides will soon not be an option for many. 

Scientists at AgResearch, Lincoln are developing pesticides that are toxic only to the target pest, have little or no impact on non-target species, and fewer associated environmental hazards.

Bio-pesticides are natural pesticides made from microorganisms (such as bacteria, viruses, fungi, protozoa and nematodes) or their products. Effective bio-pesticides are needed to control existing pests and diseases, and those emerging as a result of land-use change, farming intensification, climate change and biosecurity breaches.

Global pressure for nil residue produce has led to international withdrawals of many chemical insecticides widely used by New Zealand farmers. The gradual withdrawal of chemical pesticides will leave growers with few or no alternatives to control pests and diseases that can cause major production losses.

The Next-Generation Biopesticides programme is a joint initiative between AgResearch, the Bio-Protection Research Centre and Plant & Food Research, funded by MBIE. It is aiming to develop prototype biopesticides that are capable of rapid knockdown of pests and have multiple modes of action to target pest complexes and prevent development of resistance.

The programme spans fundamental and applied research, and the team is using the latest analytical techniques to discover novel bio pesticides, and develop the best formulation and delivery systems for maintaining their viability.

They are targeting a range of financially damaging pests and diseases including pasture pests such as black beetle, grass grub, porina moth, plantain moth and a range of forage and vegetable pests.

Mark Hurst is a senior scientist at AgResearch, Lincoln. His research is focused on isolation and characterisation of insect pathogens, defining their virulence attributes and making sure they are amenable to processes such as cultivation and formulation. Isolates are assessed for their mode of action, environmental persistence and properties such as non-target effects against beneficial organisms.

Work has focused on turning a naturally occurring bacteria Yersinia entomophaga into a biological pesticide that kills black beetle adults and also other pest species such as porina. The product developed in the lab was similar to slug bait and when spread out onto a paddock beetles were killed within a few days.

The second bacteria called Serratia proteamaculans has high activity against two New Zealand pasture pests: grass grub and manuka beetle. Trials have shown the bacteria to have similar efficacy as the chemical alternatives.

To apply these technologies, the biopesticides need to be cultured and processed into one of several forms tailored to fit with a particular landscape and/or insect type, these include biopolymers, seed coat, baits and granules, that are able to be either sprayed, broadcast or drilled across paddocks.

Sarah Mansfield is an entomologist at AgResearch with a research focus on biological control and is part of the team working on bio pesticides. Among her particular areas of interest are black beetle, grass grubs and manuka beetle.

Grass grub is New Zealand’s most damaging native pasture pest. Adult grass grub beetles fly at dusk in spring and early summer. They are often attracted to light. The beetles live for a few weeks and mate – with the females laying eggs 100- 150mm under the soil. As they grow the grubs attack the roots of the pasture during late summer through to autumn.

Manuka beetle is generally considered to be a minor pest – but in the right conditions it can cause damage similar to grass grub. They can lay their eggs in soil up to a depth of 10cm. The grubs are similar to grass grub although smaller in size and often mistaken for them.

Another pest on the radar for a bio pesticide is black beetle. It is a pasture pest in the upper north island and found also in the Waikato, Bay of Plenty, Taranaki and Hawkes Bay. Larvae damage the roots of grass in summer while adults can cause damage in autumn and spring. Black beetle grubs are sometimes confused with grass grubs. Black beetle grubs grow up to 2.5cm and are not present in winter, whereas grass grub are smaller, around 1cm long in February, and only grow large in late autumn.

Bio pesticides offer different modes of action from conventional pesticides so using them efficiently requires specific user knowledge on the agent and the target pest. This also means farmers need to know when to use it, what the rates should be, and the time between applications.

Use also requires an exact identification of the pest and an understanding that they may not work as quickly on a pest as a chemical will. Efficacy may also be affected by the overall health of the soil. As well, farmers need to be aware that they are dealing with a live organism, so correct storage (for example in a cool environment) will have an impact on the life on the bio-pesticide.