Farmers battling mice plagues in W-A, South Australia, and Queensland now have a new tool in their arsenal to deal with the pest.

The Australian Pesticides and Veterinary Medicines Authority has approved Grand Producers Australia's emergency application for access to double-strength zinc phosphide mouse bait.

Grain Producers Australia Research Development and Extension Spokesperson Andrew Weidemann spoke about what the new poison will mean for farmers dealing with the plagues.