Marcus Rashford played up front alongside Jamie Vardy, and the Manchester United youngster opened the scoring with a belting long-range effort on 13 minutes that left Keylor Navas flapping at thin air.
Rashford endured a hard end to the season at United, scoring just four times in 2018 at club level, and suffering some stinging criticism from Jose Mourinho.
But two of those to come off the bench combined for England's second goal 14 minutes from time as Dele Alli's cross was headed home by Welbeck. I've not got a player in the squad who I would think twice about putting into the opening game of the World Cup.
"The players have a good mentality and we have great competition for places in all positions".
Right-back Trent Alexander-Arnold will make his England debut at some stage in the game and Southgate said he would be prepared to throw any of his squad into a World Cup starting XI.
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The update will work on any Apple device that is now capable of running iOS 11, which includes iPhone 5s and iPad Air and later. The new FaceTime will allow you to invite up to 32 people into the same video chat session, instead of just one-on-one calls.
Gareth Southgate has admitted Jordan Henderson and Eric Dier could be fighting over one place in England's World Cup side. England outpossessed Nigeria 59-41, with each team having 12 shots, four on target. "We need that competition but I'm delighted with our preparation and I feel positive about our platform leading into the tournament", he said.
Navas was representing Costa Rica at Elland Road as they faced England in a World Cup warm-up match.
One change to his side that Southgate confirmed on Wednesday is that Stoke City goalkeeper Jack Butland will start ahead of Everton's Jordan Pickford, who has been handed the No. 1 shirt.
"Anything's possible so we have to go there with the highest expectations".
It was Costa Rica's only threat in a dominant first-half display by England.