Published on 25/09/2025
It’s now been just over 12 months since AgResearch, working with Midlands Holdings and Grasslanz Technology, filed the paperwork with ACVM to register a novel biological agent called AGR96X.
In the interim, despite chlorpyrifos being under scrutiny by the Environmental Protection Authority for the past four years, the ACVM approved a new generic liquid formulation for use in NZ as recently as May 2025.
An identical product was registered the same time last year.
As of July, farmers and growers using chlorpyrifos for grass grub have 18 months to phase it out, while those using it for a wide range of other crop pests like aphids, cutworm, Argentine grass grub, leaf roller, springtails and thrips have six months.
Few submitters at the EPA reassessment hearing in April argued against the phaseout itself. But there was widespread concern about the timeline, lack of alternatives for grass grub, and potential costs for farmers and growers after chlorpyrifos and diazinon are gone.
Industry sources point out the estimated financial losses currently caused by grass grub - up to $380 million on dairy farms and $205 million on sheep and beef every year – are based on research done six years ago; show the damage that occurs even with chlorpyrifos still available, and do not represent what might occur when chlorpyrifos cannot be used at all.
They also note the native NZ grass grub is not present in other countries that have banned or strictly limited the chemical, meaning our producers are uniquely challenged.
Federated Farmers says it would be ‘disastrous’ for food production and NZ agricultural exports if farmers are left high and dry for any period without an effective control method for this pest.
AgResearch says AGR96X, a strain of the highly virulent Serratia proteamaculans bacterium, holds promise as a biocontrol for killing larvae of both the NZ grass grub and the NZ manuka beetle.
“Through more than 20 field trials located throughout NZ and assessing different crop types, AGR96X has been shown to be as effective as synthetic products.”
But even if it does get the tick from ACVM, observers say serious time and money would still be required before it could be deployed commercially at scale.
NZ-based BioStart, which developed and markets BioShield Grass Grub, says it is currently developing a second generation biopesticide targeting NZ grass grub larvae in both pastures and annual crops.
This work has been underway for the past three to four years, and has now moved from the lab to field trials.
BioShield is based on Serratia entomophila, a naturally occurring bacterium that causes amber disease, which kills grass grub larvae without harming other animals, beneficial insects, and soil ecology.