Ireland fell by 48 runs to England in Guyana on Friday and although they started well, reducing England to 113-4 at one stage, they were comfortably beaten in the end.

The South Africa Super Eights game is also in Guyana.

Johnston was particularly critical of his team's untidy fielding, which he normally considered their greatest strength.

South Africa were awarded $175,000 on Sunday for topping the one-day international rankings on the April 1 cut-off date. Ireland know they must up their performance to be competitive.

"We'll sit down and have a chat about the do's and don'ts before we go into the next game against South Africa," Johnston told reporters after the England match.

"That will probably be a tougher game with their form and with the way that they are playing their cricket at the moment.

"If we play like we did against England there's probably more of a disaster on the cards so we've got to go out there and lift it another 25 percent."

World Cup debutants Ireland, who shocked the cricket world with a victory against 1992 champions Pakistan in the group stage, have said they are aiming to avoid eighth and last position in the Super Eights.

The bottom-placed team collect $50,000 in prize money, while seventh will receive double that.