ZANDVOORT, Netherlands (Reuters) - While Bernhard Langer showed he can still challenge strongly when nearly 50 years old, his 17-year-old son Stefan plummeted to a 28-over 98 in yesterday's Dutch Open first round.

Amateur Stefan, making his European Tour debut, finished 31 strokes behind his father, whose 67 left him only three strokes off Japanese Taichi Teshima's early lead.

The young plus-one handicapper's card included a seven-over 12 on the second, his 11th, where he lost two balls and then found himself unplayable. He also shot two triple-bogeys and four double-bogeys.

While he was some distance away from Briton Mark James's all-time high of 111 in the 1978 Italian Open at Pevero in Sardinia, Stefan's was the third-worst return on the European Tour.

Bernhard, who turns 50 on Monday and will then be eligible for seniors' tours, has been European number one twice and claimed 42 European Tour titles.

The double US Masters champion said his son had been playing much better when the pair committed to the tournament six months ago, before they and their coach Willi Hoffmann began wholesale swing changes.

"When you can't do the old swing or the new, you're caught in between and scoring mounts up rapidly then," Bernhard told reporters.

"The changes are pretty severe but he has to move forward if he wants to become a good player."

As far as his son's potential as a professional is concerned, Langer added: "He's got six years schooling to come, hopefully he will get on a college team and then we'll see how he measures up. I'm not going to push him, though."

Bernhard made his European Tour debut as a 16-year-old amateur in the 1974 Swiss Open, beginning with a 77.

In being 21 strokes worse, Stefan, whose only real tournament experience is on Florida and Germany junior tours, told reporters: "It was discouraging. Tomorrow's going to be a challenge so I'm going to go away and work on some things.

"My chipping and putting was not bad but I've got to improve my driving. I hit only one fairway. This is a most punishing course if you don't drive well.

"I lost a couple of balls and the ones I found, some of them were unplayable, but I have not been confident with my swing for a couple of months.

"But I got an invitation to play and I thought it would be better than walking outside the ropes."