Zinc Phosphide - New emergency use permits

By Callen Thompson – Mixed Farming Officer, Central West Local Land Services

While the NSW Government’s emergency application for the use of bromadiolone to control mice is still being assessed by the APVMA, there are range of other already approved permits that can help Central West farmers manage mice.

Recent work by CSIRO, with investment from the Grains Research and Development Corporation (GRDC), has led to emergency permits being approved by the Australian Pesticides and Veterinary Medicines Authority (APVMA). These permits will help producers manage mice in their farming systems. However, it is important that users follow the label and the permit directions to ensure they apply the product in a safe manner.

Over the last eight months, zinc phosphide coated grain has been used throughout the Central West for crop and grain storage protection against mice. Mice are particularly damaging to crops at sowing, so producers have been controlling them in fallows and just after planting.

Recent research by CSIRO has indicated that zinc phosphide treated grain at the current concentration (25g/kg of grain), was not always lethal to all mice in laboratory conditions. The CSIRO research indicates that higher concentrations can increase the effectiveness of baiting. Grain producers Australia has applied to the APVMA for an emergency permit which will allow bait producers to increase the concentration to 50g/kg, which will greatly increase effectiveness.

The APVMA has also approved two other emergency permits relating to zinc phosphide. One permit submitted by The NSW Department of Primary Industries allows producers to spread the 25g/kg concentration product at 1kg/ha to bare ground prior to planting. The other permit allows for the 25g/kg concentration product to be spread at rates of 3-5kg/ha as long as it is in stubble or thick ground cover.

Before producers apply zinc phosphide treated grain, they should read the label and read the permit. There are constraints on use, buffer zones and timelines that must be adhered to. Zinc phosphide treated grain is a valuable tool for protecting crops against mice, but it can be very dangerous to the user, to stock and to the environment if not used correctly.

It is also worth remembering that baiting is less effective if there are other food sources around. At sowing, baiting is often most effective if done within 24 hours after sowing. The following GRDC factsheet has some great advice: https://grdc.com.au/resources-and-publications/resources/mouse-control

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