The cost of annual produce was set to increase following cyclone Gabrielle, agricultural minister said.
Areas rural of Northland are still struggling with flooding, power outages and slips days after the cyclone hit the area.
Following the announcement of $4m to help farmers and rural communities, minister Damien O'Connor said they will need additional funding.
"Producers, farmers and growers are very resilient and this has hit some of them very very hard, there will be some shortages in some areas," O'Connor said.
"It will impact on their ability to get the crops off to harvest and the ability to get a lot of that produce into the New Zealand markets.
"There will be some shortages in some areas and that probably will affect prices, but at this stage it's hard to know when and where those impacts might be felt."
He said up to 50 percent of kūmara crops had been destroyed in Northland.
"Yesterday I visited growers in Northland in kūmara-growing areas where the impacts on the annual crops will be quite severe.
"The cyclone caused up to a 50 percent reduction in kumara availability in the New Zealand markets - that will have great impacts there," he said.
The Government is providing an initial $4 million to help farmers, growers, whenua Māori owners and rural communities mobilise and co-ordinate recovery efforts from Cyclone Gabrielle.
The breadth of this storm's impact is unprecedented, with milk collection disrupted, orchards inundated and livestock losses across much of the North Island.
In a statement, the government said this was a dynamic situation and they would respond accordingly to help the rural sector to respond with this initial funding of $4 million.
Speaking to RNZ today, O'Connor said there would be more support needed as they uncovered the true extent of damage.
"There will be additional funding and government has already announced that through MSD, there is direct support for those people who need it," O'Connor said.
Geoff Crawford of Crawford Farms near Whangārei, said the cyclone wreaked havoc in the Hikurangi Swamp.
"We farm about 500 hectares of land on the Hikurangi Swamps, 450 hectares of it is under water at the moment.
"The Hikurangi Swamps is around 5200 hectares, probably 4500 hectares is under water" said Crawford.
Up to 90 percent of kūmara crops have been destroyed, he said.
"It's quite significant, it's going to be a major blow to the New Zealand economy.
"There's not going to be any kūmara from us this year."
Northland Federated Farmers chief executive John Blackwell said he had been disconnected from civilisation.
"I think a lot of people are still stunned, it's hard to believe that we've had so many weather events in New Zealand this year - and we're only in the second month," Blackwell said.
Much of the kūmara supply comes from the Kaipara district, but this year there would be a shortage.