The 39 year old Alker reached the turn in a four under par 32 after a hattrick of gains from the fifth, and he was joined on the mark by former Irish Open winner Finch and Saint Omer Open champion Wiegele, who were both through eight holes.
Wiegele, 32, eagled the first before adding back-to-back birdies at the sixth and seventh, while Finch mixed five birdies with a bogey at the second.
England's John Bickerton was one behind after eight holes at Luxehills International Country Club, while Michael Campbell was amongst those on two under as his revival continued.
The former US Open champion from New Zealand had made only four cuts in two years a month ago as he battled a string of injuries.
But he has made three of the last four on The European Tour and two birdies on his outward nine set him on the right track again.