Dahlia bulbs could be hard to come by next season because of concern about a viroid which affects potatoes and tomatoes.

Most imported dahlia bulbs come from the Netherlands, and the Ministry for Primary Industries says the Netherlands can no longer provide Pest Free Area (PFA) certification for the potato spindle tuber viroid (PSTVd).

Biosecurity New Zealand animal and plant health acting director Lisa Winthrop says this exotic pest is a threat to New Zealand's potato, tomato and avocado industries, and is known to be present on dahlia bulbs overseas.

Biosecurity New Zealand has been working with the Netherlands to provide a solution to allow the import of Dahlia bulbs, says Winthrop.

Kings Plant Barn general manager Chris Hall says previously, importers only needed to get one field tested for the whole nursery to be approved, but now they may need to test the numerous varieties individually.

"The cost is now prohibitive for the grower to do this," Hall says, "because New Zealand is the only country demanding this, so they have decided to probably not bother and sell them elsewhere. Because the demand for dahlias worldwide is huge at the moment."

There were a few local backyard growers of dahlias in New Zealand, but Netherlands was the main supplier of dahlia bulbs, he says.

The removal of the PFA for PSTVd by the Netherlands also affects plants from the chrysanthemum, diascia, persea, petunia, and solanum genera - none of which have been imported since 2020.

-RNZ.