Australian customs officials destroyed two irreplaceable plant specimens that were being loaned to scientists by international institutions, prompting one of the institutions to suspend all transfers to Australian scientists.

The Department of Agriculture has conceded that missteps occurred while enforcing strict quarantine laws, when it accidentally incinerated the lichen specimens.

Lichen and moss grow on the trunks of chestnut trees at Nutwood Farm at Mount Irvine. Credit:Wolter Peeters

France's National Museum of Natural History and New Zealand's Landcare Research Allan Herbarium had sent the samples, which dated back to the 19th century, to help with Australian research, but they were intercepted by customs officers due to inaccurate paperwork.

A department spokesman said the packages did not give any indication of the intrinsic value of the samples, and the customs officers held onto them for longer than they were required before deciding they posed a potential biosecurity threat and incinerating them.