New Zealand's agriculture-based economy is at risk from falling bee numbers and the threat of exotic bee species, an ecology expert warned Tuesday.

University of Canterbury Professor Jason Tylianakis said New Zealand exported 80 percent of its food production and crops such as kiwifruit, clover, apples, canola and honey could suffer.

Between 60 percent and 75 percent of all food crops required animal pollination, he said in a statement.

New Zealand's wild honey bees had basically been eliminated by the invasive varroa mite, which beekeepers kept at bay with chemicals, he said.

But if the mite developed a defense, then the country's 430,000 managed hives, which were worth about 5 billion NZ dollars (4.18 billion US dollars) a year to the economy, could be threatened.

"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," said Tylianakis.

New Zealand was also vulnerable to invasive bee species, such as the Asian honeybee, which had taken root in Australia and would be an "environmental catastrophe" if it reached New Zealand.

"The Asian honeybee is a very aggressive invader and can no longer be feasibly eradicated there. Although it is named a honeybee, it is aggressive and almost unfarmable," he said.

"We recently received the wool carder bee here in New Zealand, but this doesn't form large colonies so it's not so problematic yet. It remains to be seen what impact it will have on our native bees and plants," said Tylianakis.

"In contrast the Asian honeybee forms colonies which can move up to 10 km 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, they're a primarily tropical species, so hopefully they wouldn't do so well here, unless climate change warms us up."