Shiitake mushroom lovers are being warned that some of the mushrooms labelled as New Zealand grown may actually be imported from China.
An increasing number of shiitake mushroom growers have switched to using imported Chinese growing 'logs' on which the fungi is grown, because it is cheaper than using New Zealand-made logs, reported RNZ.
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The logs are plastic bags filled with sawdust and water, inoculated with shiitake spawn and shipped to New Zealand.
Hillcroft Mushrooms co-owner Bruce Mackinnon told RNZ that the mushrooms, harvested just a few weeks after arrival, are often then sold as being New Zealand-grown.
However, he said the substrate and none of the inputs were from New Zealand.
"The whole thing is done in China and imported here. New Zealand customers are getting hoodwinked," he told RNZ
Mackinnon said his shiitake sales had fallen "around 80 percent over the last two years" as his competitors switched to cheaper imported growing logs.
The country's largest mushroom grower, Meadow Mushrooms, launched its "New Zealand grown" shiitake mushrooms earlier this month which it said were all grown from Chinese logs.
Meadow Mushrooms marketing manager Melanie Rushton told RNZ that the packaging complied with Australian and New Zealand standards.
"Because effectively we are producing the mushrooms here to New Zealand safety standards in a controlled environment, and they're being grown here using our resource and our expertise, water and all of our facilities.
"We didn't want to mislead anybody, so checked with Australian and New Zealand standards to make sure we were okay to be able to say that."
There's concern that there could be health issues with the imported mushrooms, given China's poor environmental record.
Samples from mushrooms grown on New Zealand and Chinese logs had been tested at Massey University showing detectable" amounts of arsenic lead on the Chinese ones.
A Commerce Commission spokesperson told RNZ that was "no hard and fast rules" to determine whether a product was New Zealand made or grown.
It said it was aware of the imported mushroom issue, but it was not investigating.