Alternative Grass Grub Weapon Now Urgent

Scoop

15-07-2025

Federated Farmers says urgent action is needed to plug a looming gap in treatments to fight native grass grub, which costs the agricultural sector hundreds of millions of dollars each year.
"This is our biggest agricultural pest by a country mile, yet there's a real risk farmers' arsenal to fight it will soon be empty," Feds biosecurity spokesperson David Birkett says.
"It's pleasing that manufacturers have work developing new chemicals underway.
"We also need the Environmental Protection Authority to prioritise and fast-track their assessment of any new options."
Costelytra giveni is a scourge for pasture and lawn, and also a risk to horticulture and native plant root systems.
The two most effective chemicals to control the grub - chlorpyrifos and Diazanon - are both being phased out after decisions by the EPA to ban them.
Chlorpyrifos, a broad-spectrum organophosphate insecticide, is banned in the European Union and Canada, and its use is heavily restricted in Australia.
It is in the process of being phased out internationally via the Stockholm Convention, of which New Zealand is a signatory.
The EPA recently consulted on banning chlorpyrifos here. After considering new information, and holding a public hearing, a decision-making committee found risks to people and the environment - especially to those spraying it - outweighed the benefits.
"We're pleased the EPA listened carefully to our submission, and decided that for the agricultural sector, the ban would come at the end of an 18-month phase-out period," Birkett says.
"However, stocks of chlorpyrifos are already very limited and in the face of bans, manufacturers are taking it out of production."
The other potent weapon for combating grass grub, Diazanon, will also be banned from 2028.
Federated Farmers understands AgResearch and ag chem companies are well underway with developing a new tool for combatting grass grub.
"We'd really like to see them accelerate that development work. It would be disastrous for food production and our agricultural exports if our farmers are left high and dry for any period without an effective control method," Birkett says.
A 2018 study said native scarab grass grub causes losses of up to $380 million on dairy farms and $205 million on sheep and beef farmers every year - and that was with access to chlorpyrifos.
Birkett says the EPA also needs to play its role swiftly.
"Federated Farmers has been critical of the EPA's failure to get on top of a backlog of assessment applications for agri-chemicals and animal health treatments.
"We've welcomed Government announcements on new measures aimed at streamlining assessment processes, particularly in cases where chemicals are already being used safety in other countries.
"But the the EPA also needs to adjust its priorities and not focus on assessing generic chemicals that are already available," Birkett says.
"Their work stream needs to take better account of how far off approvals are for effective replacement products, including biosecurity and pest increase issues, and how much delays would cost the country.
"The new chemicals that offer the greatest economic benefits should get priority in the queue - and I would put any new treatment for grass grub in that category," Birkett says.