Winning the toss and choosing to bat first Sri Lanka A ran up their second successive total in excess of 300 when they rattled off 337-5 off the Irish bowling.
Ireland’s run chase was derailed by fast bowler Isuru Udana and spinner Kamindu Mendis as they slumped to 53-6 and after making a recovery of sorts reaching 162-7 collapsed against Siriwardana to lose their last three wickets without any addition to the total.
Siriwardana brought a swift end to the Irish innings by capturing three wickets in his fifth over without conceding a run to finish with figures of 4 for 26 of 4.5 overs. Udana and Mendis two wickets apiece.
Milinda Siriwardana who destroyed the Irish batting with four wickets for 26 runs appeals for a wicket.
The highlight of the Ireland innings was a 67-run seventh wicket stand between Mark Adair (43) and Shane Getkate (56) after which they folded up tamely.
Earlier an opening stand of 86 off 76 balls between Avishka Fernando (55) and Tharanga provided a solid base for Sri Lanka to launch their innings.
Tharanga batted with authority to score 103 off 112 balls inclusive of 13 fours and a six.
A further partnership of 126 for the fifth wicket between Angelo Perera (72 not out off 62 balls, 7 fours) and Mendis (76 off 50 balls, 9 fours, 1 six) provided the final impetus to the innings.
The two teams travel to Colombo for the three remaining ODIs. The third and fourth will take place at the SSC on January 24 and 26 and fifth and final at the R Premadasa Stadium on January 29.
Scores: Sri Lanka A 337-5 in 50 overs (Avishka Fernando 55, Upul Tharanga 103, Angelo Perera 72 n.o., Kamindu Mendis 76, James Cameron-Dowe 1/32)
Ireland A 162 in 35.5 overs (Mark Adair 43, Shane Getkate 56, Isuru Udana 2/6, Kamindu Mendis 2/33, Milinda Siriwardana 4/26)