Without EU workers, Britain's horticulture industry would collapse, experts have warned.
Thousands of people travel to the UK each year to pick fruit and vegetables, allowing home-grown businesses to flourish, employers said, but they fear possible changes to freedom of movement for EU nationals could have a devastating effect.
People from elsewhere in the EU currently make up 7% - 2.15 million - of the UK workforce, according to the latest figures from the Office for National Statistics.
Both seasonal workers, who come to the UK when crops are ready to be picked but return home out of season, and those who have graduated into permanent management positions within horticulture make a huge contribution, Dr Chris Hartfield of the NFU said.
He told the Press Association: "They underpin the entire fruit and vegetable production in the UK so I would say that is a massively positive contribution.
"Without them we simply wouldn't have an industry.
"And without them consumers would struggle to find British-grown fruit and veg on supermarket shelves."
Dr Hartfield, chief adviser on Horticulture and Potatoes, said he believes there is a lack of understanding among the British public about how the industry works, and how fruit and vegetables make it onto the kitchen table.
He said: "We need to help them understand actually there are some realities about the production of that and one of the realities is that the production of that fruit and veg is hugely reliant on hand labour and the majority of that hand labour is non-British citizens from elsewhere in Europe."
In the 12 months to March 2016, 630,000 EU citizens became newly eligible to work in the UK, figures from the Department for Work and Pensions show.
Following the UK's vote to leave the EU some workers have said they no longer feel wanted here.
Nick Ottewell of salad and cereals producer Laurence J Betts Ltd, based near West Malling, Kent, a firm heavily dependent on seasonal workers, said his employees have been approached while shopping at the supermarket and told "You're not welcome any more".
He said: "They don't feel the love at the moment. They feel that they are in a country where they are not wanted."
Dr Hartfield said growers do try to recruit from within the UK but described it as a "massive challenge" because typically British workers want permanent jobs and do not want to do that kind of work.
"Their preference is elsewhere," he said.
An online campaign has been launched to highlight the contribution made by EU workers in the UK.
Known as #blEUmonday, the so-called workplace protest is encouraging people to wear blue and spread the message that workers from other EU states have a positive impact in Britain.
Within the industry, berries account for more than one pound in every five spent on fruit, chairman of British Summer Fruits Laurence Olins said.
"We know the consumer wants to buy locally produced food, that's a given," he said.
Without EU funding, which has allowed horticulturists to erect polytunnels and packhouses, and EU labour, Mr Olins said the industry faces a bleak future.
"Our industry would be dead, in the water dead (without EU workers). No farmer is going to grow a crop he can't pick."
He added: "Our industry is a success because of EU labour and EU funding."
He called for a scheme to be set up to allow for the required numbers - in the berry industry alone as many as 50,000 people each year - to come to the UK, but said even that will cause hassle for employers who will probably have to contend with red tape.
He said: "There will be a cost, maybe because it's going to be limited it will be done by official authorised labour providers, agencies, whereas now a grower, and many do, set up their recruiting offices in eastern Europe and do it themselves. That probably will not be allowed - I am jumping ahead now. But all I can say is it is incredibly easy now; it will be harder (to bring people over)."
He said that, despite promises from those within the Leave campaign about permit schemes in the event of Brexit, he had heard "nothing from any of the candidates to date about anything to do with this".
He added: "I would suspect it is way down on their list of priorities hence the reason why we are putting it way up on our list of priorities."