CHRISTCHURCH: Trent Boult needed just 15 balls to change the complexion of the second test against Sri Lanka on Thursday when the New Zealand seamer took six wickets in a devastating spell to ensure his side took complete control at Hagley Oval in Christchurch. Boult finished with career-best figures of six for 30 to help bowl out the visitors for 104, giving New Zealand a valuable 74-run first innings lead in the series decider. Jeet Raval (74) and Tom Latham (74 not out) then put on an 121-run opening partnership, while captain Kane Williamson scored 48 as the hosts took firm control of the game. Ross Taylor was unbeaten on 25 alongside Latham at the close of play on the second day with New Zealand on 231 for two and holding an overall lead of 305 runs. Sri Lanka had resumed on 88-4 with first test centurion Angelo Mathews on 27 and Roshen Silva on 15, and appeared to be comfortable as they looked to take a big chunk out of New Zealand’s modest first innings of 178. After starting play with figures of 0-20 from 10 overs, Boult then produced one of the most destructive spells in test cricket as he took six wickets for four runs in the space of 15 balls, including three victims in four deliveries.