text: Wasps goalkeeper Neil Parry had already denied Dobbie three times before the striker curled in a drive off a post.
  Parry saved again from Dobbie after the break, but the 33-year-old would not be denied his fifth goal in three Challenge Cup outings and 12th goal of the season for the Championship side.
  His close-range header killed off the lively League One visitors' hopes.
  And it ended a run of eight games without a victory for the Dumfries side - a sequence that had ended with Gavin Skelton standing down as manager earlier this week.
  The side under caretaker Jim Thomson, who had been football development manager, for the first time became the second into the last four.
  Dundee United had earlier beaten Dunfermline Athletic 1-0 at East End Park.
  League One leaders Livingston host Welsh champions The New Saints, while Ayr United visit Championship rivals St Mirren, in two Sunday quarter-finals.
  A Grant Anderson header had grazed the Alloa crossbar before Dobbie made the breakthrough at Palmerston Park.
  The Wasps had their moments, with Jamie Longworth being denied by goalkeeper Lee Robinson and Greig Spence going close with an overhead kick with Jim Goodwin's part-time side only one goal behind and looking the more likely to score.
  However, after Parry prevented Derek Lyle extending the lead, Dobbie provided the finish from Dean Brotherston's cross 14 minutes from time.
  Queen of the South caretaker manager Jim Thomson: "It was a shock to myself. On the Monday, Gavin just decides to resign. I think it was a combination of things.
  "It has been a terrible run and hopefully that brings a bit of confidence to the squad.
  "It has been a hard week for everybody, but the way the boys trained during the week, the tempo they took into the game.
  "I thought in the first half we were excellent. Some of their play was brilliant.
  "It is a break from the league for the boys and it's a national cup semi-final so you always want to progress."
  Alloa Athletic manager Jim Goodwin: "We came here to be positive and to take the game to Queen of the South. I thought we done that for large spells of the game.
  "They're very lucky to have Stephen Dobie, who's a top player.
  "He's the type of player who could easily be playing in the Premiership.
  "I'm proud of the players. We didn't just come down here and look to hang on. Overall, there's a lot to be positive about."
target: Stephen Dobbie's double took Queen of the South into the Challenge Cup semi-finals at Alloa Athletic's expense.