Warwickshire County Cricket Club failed to build on the good work in the third day of their County Championship game against Somerset.
Warwicks started the third day at Edgbaston on 283-3 with Ateeq Javid 103 not out and Laurie Evans 130 not out.
But as soon as Evans was trapped lbw by Trego after adding eight more to his score, with the score on 307, wickets started to be given away cheaply.
Tim Ambrose was trapped lbw for 12 and Rikki Clarke was run out one run later, before Javid was finally out caught behind by Craig Kieswetter for 133 to give George Dockrell his third wicket.
Darren Maddy made an unbeaten forty but Dockrell struck to take the wickets of Barker for five, Tom Milnes for two and Jeetan Patal for 20 as Warwicks lost six wickets for a hundred runs and finished 407 all out.
Somerset, some 67 runs behind, came in and put on 81 on the board before Trescothwick was out for 27 to a catch from Clarke off the bowling of Patal.
Nick Compton ended the day on an unbeaten 83 and an over before stumps, Chris Jones was run out for sixteen to see Somerset close on 133-2, a lead of 66.