Lara was on an unbeaten 60, while Ganga was 45 not out at the close of Day 2 at Guaracara Park. Trinidad reached 126 for two, still 220 behind Guyana.
Pacer Esuan Crandon struck two crucial early blows for Guyana as they restricted Trinidad to 32 for two at tea. He bowled Tishan Maraj for two, and had Lendl Simmons caught at the wicket for six. Lara struck five fours on 104 balls in 134 minutes.
Earlier, the spin and pace tandem of Sanjeev Gooljar and Reyad Emrit helped Trinidad dismiss Guyana shortly after lunch.
Leg-spinner Gooljar picked up two of the four wickets to fall in the morning session, while Emrit got three for 72.
In St Lucia: A rain-soaked outfield prevented play for the second straight day between the Windward Islands and the Leeward Islands at the Mindoo Phillip Park.
The umpires suspended the match after showers Friday night and early Saturday left the outfield soggy. Friday's play was also called off due to rain.
Both teams need a result in this fixture to improve their standings in the six-team tournament, currently led by Barbados with 24 points. (AP)