The plight of bees could have a hefty impact on the New Zealand economy, a University of Canterbury ecologist says.
Ecology professor Jason Tylianakis said New Zealand exported 80 per cent of its food production, and crops such as kiwifruit, clover, apples, canola and honey could suffer as the bee population decreased.
"An agricultural economy like ours depends strongly on pollination, and between 60 and 75 per cent of all food crops require animal pollination," Tylianakis said.
"Wild (feral) honey bees have basically all been eliminated by the varroa mite.
"Beekeepers are still able to keep hives alive by chemically eliminating varroa. But if it involves defence (which insects and mites tend to do when sprays impose a large selection pressure) then managed hives could be threatened.
"Wild native and exotic bees (apart from honeybees) are in decline worldwide, including New Zealand."
Tylianakis understood the real value of honey bees working about 430,000 hives was $5 billion a year to the economy.
"We need to manage our agriculture in a way that protects native bees and pollinating flies. We need to reduce the use of insecticides and provide some areas of unsprayed, uncultivated habitat with food and nesting sites in agricultural landscapes."
Australia was considered a major biosecurity threat for New Zealand beekeepers, largely because of the transport between both countries. However, in terms of countries with a similar climate, New Zealand could receive invasive species from a lot of places. Australia had the troublesome Asian honeybee.
"The Asian honeybee is a very aggressive invader and can no longer be feasibly eradicated there," he said. "Although it is named a honeybee, it is aggressive and almost unfarmable ... If it came here to New Zealand it would be an environmental catastrophe."
New Zealand was recently invaded by the wool carder bee but it didn't form large colonies. Tylianakis said it remained to be seen what impact it would have on native bees and plants.
"In contrast, the Asian honeybee forms colonies which can move up to 10km from their nest sites. They aggressively protect their nest sites, so could compete with bees. They're also a host of varroa, so they could serve as a vector for the mite."
However, it was a mainly tropical species, so hopefully it wouldn't do well here.