An Alan Forrest hat-trick gave Ayr all three points and extended the sorry Sons’ winless streak to eight games.
United boss Ian McCall said: “That’s Alan got seven goals this season and he is playing as an out and out centre forward and he is a wide player, but needs must. It was great for him. He has a great attitude.”
Ayr made a terrific start when they went in front after just three minutes. Josh Todd’s slack pass in midfield was intercepted by Paul Cairney who threaded a pass through to veteran Gary Harkins. His 15-yard angled drive was well saved by goalkeeper Alan Martin, but Forrest was well positioned at the back post to knock home the rebound.
United threatened again after 23 minutes when the impressive Harkins cut in from the right and curled an 18-yard left-foot shot which forced Martin into a full-length save to push the ball wide.
The visitors finally got the second in 50 minutes after an error by ex-Ayr goalkeeper Martin, who allowed Harkins to square the ball for Forrest to drill it into the empty net from 12 yards.
Forrest completed his hat-trick from the penalty spot in 61 minutes when Daniel Harvie sent captain Nicky Devlin sprawling in the box.
The Sons’ best effort came in 69 minutes when Sam Stanton’s fierce 18-yard shot was turned over by goalkeeper Greg Fleming, to complete a hat-trick of shut-outs.
Dumbarton boss Stevie Aitken said: “Right from the off it was woeful and not good enough and the way we lost the goals summed it up.”