Chlorpyrifos ban in New Zealand sparks concerns over grass grub control

The Environmental Protection Authority (EPA) is banning chlorpyrifos, after reassessing the chemical. The ban will come into effect progressively during an 18-month phase-out period.

Chlorpyrifos is a broad-spectrum organophosphate insecticide used to control pests in pasture and grain corps such as wheat and for biosecurity treatment of pests.

The chemical 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.

As part of the reassessment, the EPA considered new information, called for submissions, and held a public hearing. A decision-making committee found that risks to people and the environment from using the insecticide outweighed the benefits.

"Operators spraying the insecticide and bystanders are most at risk from immediate and long-term health issues," says Dr Shaun Presow, hazardous substances reassessments manager.

New evidence shows that even full personal and respiratory protective equipment doesn't fully mitigate the health risks.

"The health risks for children exposed to chlorpyrifos in particular are concerning, which is why we have put in place an immediate ban on using the chemical in public places," says Presow.

"Chlorpyrifos also has harmful effects on plants and animals on land and in waterways."

However, farmers warn that the ban means there's a real risk farmers' arsenal to fight grass grub will soon be empty.

Feds biosecurity spokesperson David Birkett says Costelytra given (grass grub) is the biggest agricultural pest by a country mile.

He says it's a scourge for pasture and lawn, and 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.

"It's pleasing that manufacturers have work underway developing new chemicals. We also need the EPA to prioritise and fast-track their assessment of any new options."

Birkett is pleased that the EPA listened carefully to its submission and decided that, for the agricultural sector, the ban would come at the end of an 18-month phase-out period.

"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.

New Tools in the Pipeline

Federated Farmers understands AgResearch and agrichemical companies are well underway with developing a new tool for combating 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," David 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 safely in other countries.

"But 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.