Young onions ready for planting out. Photo Plantuitjes.nl

Seven onion growers have been fined a total of over €4m by the Dutch competition authority NMa for forming a cartel to keep prices high.

The NMa says the seven firms reached a deal in 2009 to destroy part of their onion fields in order to reduce supply. This, they hoped, would keep up the price of onions.

The seven firms control some 80% of the country’s onion nurseries.

The investigation was started following a tip-off, the NMa said on its website.

Last June, the NMa fined silverskin onion growers for making agreements to limit production between 1998 and 2010 in an effort to drive up prices. The five companies were responsible for some 70% of European silverskin onion production.