TIA warns of Varroa mite risk to Tasmania

Tasmania’s fruit, berry and seed crops are at risk if Varroa mite infiltrates the state, due to a reliance on feral honey bees for pollination.

Apple production in the Huon Valley would be particularly impacted, according to a study by the Tasmanian Institute of Agriculture (TIA).

Managed honey bee colonies can be monitored and treated for Varroa by beekeepers, but feral honey bee colonies are unmanaged and likely to be at greater risk if Varroa becomes prevalent in Tasmania.

TIA entomologist Dr Jonathan Finch said many agricultural crops in Tasmania rely on feral honey bee colonies for pollination.

“International experience suggests that Varroa can reduce feral honey bee populations by more than 90 per cent within several years of establishment. A major decline in feral honey bees could reduce pollination services currently supporting Tasmanian crops, including fruit, berry and seed crops,” Dr Finch said.

“Apple production, particularly in the Huon Valley, showed the strongest evidence of reliance on background pollination services, including feral honey bees.

“If feral honey bee populations decline due to Varroa, apple growers who currently use few or no managed hives may need to review their pollination plans.”

The study found vegetable seed production was highly dependent on managed hives.

“If Varroa increases the cost and complexity of maintaining strong hives, that could have implications for seed growers as well as fruit and berry growers,” he said.

Tasmania is currently Varroa-free but if it were to enter the state the impacts to agricultural industries would be significant.

The study examined extensive grower and industry survey data. Growers also provided valuable information about how many managed honey bee hives they place in crops during flowering.

“Managed and feral honey bees cannot be distinguished by eye in the field, so directly measuring the contribution of feral bees is difficult,” Dr Finchsaid.

“By comparing grower-reported hive use with published benchmark rates, we can identify crops where managed hive use appears lower than expected. That does not prove all the remaining pollination is coming from feral honey bees, but it does indicate where background pollination services may be important.”