Their comments follow the release of a survey of 75 growers by the Green Party yesterday, which found supermarkets were adding mark-ups of up to 500% while growers were often forced to sell produce at less than cost.
The survey found 15% of growers reported their businesses ran at a profit, while 87% were forced at times to sell produce at less than cost, and 75% thought supermarket mark-ups on fresh produce were far too high.
One Dunedin grower contacted yesterday - who would not be named for fear of repercussions - said he was not surprised by the survey's findings.
It was not uncommon for a single head of broccoli sold by the grower for 50c to end up on sale in a supermarket for $2 or $2.50, the grower said.
"From what I have observed, it [the mark-up] is probably about 100%, at least ... 200% sometimes, and sometimes it could be a lot more."
The grower was one of a dwindling number inside the city's limits, and sold to a wholesaler who on-sold the produce to supermarkets.
The grower could refuse to sell to the wholesaler if the price on offer was too low, but "nine times out of 10 you have got to accept it".
"Where else are you going to go?"The wholesaler, in turn, faced pressure to keep its prices low to secure a sale to the supermarkets, who could afford to "shop around" to get the best prices, the grower said.
"The supermarkets wield the big stick.
We just do what they say.
They say `jump' and we say `how high?'."
Another Dunedin market gardener, Ray Goddard of Sawyers Bay, stopped selling to supermarkets nearly a decade ago, after voicing concerns about the downward pressure on prices.
Contacted yesterday, he said he now only sold to the Otago Farmers Market, but believed "ridiculous" supermarket prices were to blame for a dramatic decline in the number of market gardeners in Dunedin.
"Most of the local growers have gone out of business in Dunedin.
"We have gone from about 35 growers down to about five.
"They have made growing produce so unprofitable there's just so few growers left now," he said.
Crystal Gardens owner Erika Colby, of Queenstown, said her business catered to local restaurants through a wholesaler, rather than selling to supermarkets.
Even so, the prices they received were constantly under pressure, as the wholesaler competed with cheaper supermarket produce.
"Our margins are constantly squeezed," she said.
The number of growers in the region was "dropping all the time", as many selling to supermarkets found themselves "over a barrel", she said.
"The future could be quite bleak for a lot of growers."
Green Party food spokes-woman Sue Kedgley said pricing practices should be investigated and a Supermarket Code of Conduct drawn up, as "unfair" behaviour by some supermarkets was "decimating" growers and putting their industry at risk.
It appeared the two main supermarket chains - Foodstuffs and Progressive Enterprises - were using their duopoly position to drive prices down to unsustainable levels, she said.
Tony Carter, managing director of Foodstuffs (which owns Four Square, New World and Pak'n Save), told the Sunday Star Times it was "simply incorrect" to say mark-ups were 100%-500%, but would not say what they were because it was "commercially sensitive".
Peter Smith, managing director of Progressive Enterprises (Foodtown, Woolworths, and Countdown), said pricing information was "market-sensitive and varies on a daily basis".
