Berry Gardens managing director Nick Marston, speaking at Fruit Focus, held at East Malling Research in Kent last week, said growers' returns were suffering from the hard winter this year and the reduced pack size being sold by two large retailers.
The smaller pack size means that Berry Gardens is producing more packs for the same amount of fruit - an extra cost that is affecting growers' returns.
Marston said: "It's been a tough market during these past two-and-a-half weeks. After a hard winter the season started, on average, a week later. As a result we have sold seven per cent fewer strawberries to the week ending 10 July than in 2009.
"The average direct sale price achieved by Berry Gardens over the same period has moved upward slightly. But the move by two large retailers into 400g pack weights this year compared to the 454g packs sold last year - a reduction of just under 12 per cent has increased supply chain unit costs resulting in deflation of the net return to growers."
He added: "The number of packs sold was up on last year through June and early July but the move to a 400g pack weight has reduced the overall tonnage sold by some retailers. A combination of this and increased production caused by the late season followed by very hot weather has created a level of oversupply across the industry over the past two weeks with the need to sell fruit in considerably larger volumes than in 2009, which will have further lowered the net average returns for growers. How do we manage that? More early production."
Marston explained that Berry Gardens growers had reduced their production area by around seven per cent. But their switch to more intensive cultivation techniques such as tabletop strawberries should result in a similar volume being produced to 2009 by the end of this season.
He also said there had been great support from retailers for British strawberries with television advertising, newspaper adverts and magazine recipes - including those from Delia Smith and Heston Blumenthal - all of which helped to overcome the effect of the short-lived World Cup.
Retailers are also selling more premium lines, sales of which suffered last year because of the recession.
Berry Gardens Growers chair of Marion Regan said: "Retailer focus has returned and moved away from discount lines. Driscoll Jubilee has now established itself as the premium strawberry - and we now have a 90 per cent share of the market of premium strawberry sales."
Marston added: "Overall we expect to increase the amount of Driscoll Jubilee sold by around 35 per cent by the end of 2010 compared to last season."
The hard winter has delayed this year's raspberry season by two weeks but Berry Gardens still expects to sell 20 per cent more in 2010 than in 2009.
The company said it also expects to modestly increase the amount of blackberries it sells by the end of the year.
Chair Marion Regan said: "We are trying to increase our production of better eating blackberry varieties and we are very pleased that Marks & Spencer is offering its customers a 100 per cent best eating varieties offer, which includes Karaka Black, Driscoll and Driscoll Cowles.
"The packs are labelled with clear consumer messaging that these are sweet eating dessert blackberries, which will help build demand for the fruit and our blackberry business in future."