New risk-based zoning approach endorsed

10 Sep 2023

NSW Department of Primary Industries (NSW DPI) will undertake a new risk-based approach to all new emergency zoning in the ongoing fight against the destructive Varroa mite.

NSW DPI Deputy Director General - Biosecurity and Food Safety, John Tracey said the National Management Group has endorsed a proposal from NSW that zoning distances could be different depending on the individual risk of each infestation.

“The Response has 14 months of experience understanding levels of risk for Varroa mite spread, and as we have recently demonstrated in the almond pollination sites in southern NSW, a different approach can be effective,” he said.

“Where infested hives have been recently moved, have low mite levels and a clear link to an older Eradication zone, the risk profile is actually very low, whereas in situations where infested hives have been present for a long time, have high mite loads or unclear tracing links, the risk is high.

“Using this risk-based approach will reduce the impact of the response on industry and applies a scientific approach to decision making which will also be cost beneficial and help manage the resources we are utilising in Australia's biggest ever plant pest emergency.”

This risk-based approach proposes assessing new regional outlier infestations based on a combination of factors including mite load, length of time hives have been present and tracing linkages to assess the risk profile of a zone and determine appropriate zone sizes.

Where zones meet the acceptable level of protection, a reduction in zone size could be considered. Where zones do not meet this level of protection a larger zone, or the standard 10km/25km zones should be maintained.

Dr Tracey said the standard zoning strategy remains essential for larger eradication emergency (red) zones such as Newcastle, Central Coast and Kempsey.

"It has also been important during the delimitation of the Newcastle and Central Coast outbreaks due to the high number of infested premises, risk of natural spread of mites and length of time the infestation has been present.

“This system was also implemented prior to the response thorough understanding and mapping of epidemiological networks, the strict movement restrictions being put in place, and very significant levels of surveillance being completed.”

NSW DPI is the lead agency in the National Varroa mite response, which is a collaborative approach developed by the Consultative Committee on Emergency Plant Pests (CCEPP), governed by the National Management Group (NMG).

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