The visitors were depleted by several positive coronavirus cases and the game's decisive moment came after 54 minutes when Manny Duku's cross was deflected into his own net by Ayr defender Sean McGinty.
Partick Thistle lost their unbeaten start at Gayfield as Michael McKenna’s double helped Arbroath come from behind to pick up their first league win of the season with a 3-1 victory.
Kick-off was delayed because the visitors had been caught up in traffic on the way to the ground.
The Jags, though, soon settled and went ahead in the 33rd minute through an own goal from Colin Hamilton.
Arbroath were level on the stroke of half-time when McKenna scored from a free-kick, and the Lichties took the lead in the 54th minute when Joel Nouble’s cross was headed in by McKenna. Nicky Low added another four minutes later after a mistake from Jags keeper Stone.
Kyle Jacobs scored at both ends in Morton's 3-2 home defeat to Queen of the South.
Ally Roy's close-range finish put the visitors in front but Jacobs quickly equalised against his former club just after the half-hour mark following a Reece Lyon corner.
Jacobs went from hero to villain early in the second half with his own goal and Morton had a mountain to climb after 71 minutes when Ruben Soares-Junior struck to give Queens a two-goal cushion.
An own goal by Solomon Brynn saw that lead whittled away to a single goal, but Allan Johnston's team held on for their first league win of the season.