The NSW government announced they had secured 5000 litres of the anti-coagulant bromadiolone which can treat 95 tonnes of grain.

Chris Brooks, who owns a property between Mulwala and Barooga, said government action on giving farmers access to the chemical is too little too late.

"The government limited the amount of bromadiolone they can put on treated grain to a half rate, so it doesn't kill all the mice and the ones that survive are resistant to it," he said.

"The chemical isn't effective. We've created a monster because they won't eat it and even if they do they're resistant to it."

The government rollout of bromadiolone has also been criticised as being an insufficient amount to correctly tackle the problem.

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Mr Brooks said other farmers he had spoken to have used treated grain up to four times and that the effect is more like creating a "feedlot".

"Farmers are just not accustomed to laying down and dying, so what they'll do is take matters into their own hands," he said.

"They start buying pallets of Coca Cola because it's sweet and attracts the mice and they'll mix it with 24D or really volatile concoctions which they all have in their sheds and they'll wipe out the whole environment.

"Blokes will and are making alternative arrangements and mixing up their own cocktails which will have a massive detrimental effect on the environment.

"We need to get the right chemicals, the right treated grain at the right rate and the right price, to the right people to get on top of this."

Mr Brooks is seeing three mice holes per square metre on his property.

A mice burrow can house anywhere between one and four mice but could potentially hold 40.

Deniliquin-based agronomist Matt Barker said rice and maize farmers are already seeing crop losses from the mice.

"Some reports are coming back to one tonne to the hectare around the first few laps of the rice, when the rest of the paddock was going for four tonnes," Mr Barker said.

"That's a 10 tonne loss, which is considerable damage."

Rice currently markets for $640 a tonne, making the losses around $6000.

Finley dairy farmer Peter Middlebrook has noticed a significant mice presence around his property, particularly near silage.

"Out where the silage is they're starting to worry me, they're starting to burrow in through the plastic," he said.

"You see on the TV the damage they do to bags and a lot of people around here have bags."

Mr Middlebrook said that on his property spreading bait is a complicated issue, particularly around his stored grains he uses to feed cows.

"We can't put chemicals anywhere cows could get at it because if the cows eat it, it gets into the milk and we can't sell it," he said.