DEFENDING champion Thomas Pieters has been forced to withdraw from the KLM Open in Holland after he suffered an allergic reaction to a bee sting.

The Belgian, who was named as Darren Clarke's final Ryder Cup wildcard pick last month, was stung during a challenge match on Monday.

He wrote on his Instagram account: "The very unfortunate worst case scenario just happened.... One bee sting on Monday during the golf challenge against @joostluitengolfer led to a major allergic reaction with flu symptoms, and forced me to pull out of my favourite tournament of the year #KLMOpen.

"Very sorry to all the fans that are on their way to support me and to the organisation @tgsport. I owe it to you guys to defend my title next year."

There is no indication that the allergic reaction will affect Pieters's participation in the Ryder Cup, which starts at the Hazeltine course in Minnesota on September 30.

European Ryder Cup skipper Clarke said he sees signs of potential greatness in Pieters's game when announcing him as his final wildcard pick ahead of Russell Knox.

''I said all along I would not pick a rookie, I would be reticent to do so,'' Clarke said last month. ''But he [Pieters] just brings something special. He hits it so far and his short game is fantastic.

''I've been on tour for a long time and I've seen massive talent come along. I played with Tiger [Woods] when he was an amateur at the 1996 Open. I've seen Rory [McIlroy] up close since he's been a very, very young kid. Thomas Pieters impresses me in the same league as those guys. He has that amount of talent.''