Mr Ruddenklau (83) will be among more than 100 people attending the anniversary of the oldest surviving young farmers club in New Zealand.
He is believed to be the oldest surviving office-bearer attending, while Doug Gillies is the oldest surviving member.
Mr Ruddenklau was appointed secretary in 1941 during World War 2 when the club could not continue normal activities but, rather than go into recess, it remained partially active.
He gathered enough subscriptions to pay the affiliation fee and deal with correspondence.
He was appointed chairman in 1945 when the club resumed full activities.
To raise money for an honours board to recognise members who had served overseas, it was decided to hold a YFC field day - the first Five Forks gymkhana.
It was held at Fuchsia Creek in August that year, with dog trials in the morning, pony and horse events in the afternoon and a dance in the Five Forks Hall at night.
The field day raised 2, while the dance and cake raffle both raised 8 each.
The gymkhanas continued as a popular fundraising event for 21 years, except 1947, growing a "bit like Topsy" and with tremendous support from the district, Mr Ruddenklau said.
In the early years, every farm had hacks and lots of rural children had ponies.
Local pony clubs' later became involved with the gymkhana and, as motorbikes and other vehicles became more popular, the number of horses on farms declined.
John Garvan was the judge for many years and one of the most popular events was the walk, trot and gallop, Mr Ruddenklau recalled.
He said the number of former North Otago YFC members involved with organisations at a provincial level was quite noticeable and he was quite sure those that went through the movement had learned valuable skills.
