large winged flies damaging plants

by Harold Bowler
(Kempton Park Gauteng S.A.)

I have some sort of fly which is stinging my granadilla and maybe also my gems. It has wings that look to be too big for it's body which looks (without my glasses) as if it may be a shade of yellow. It may also be that they were what were stinging my peaches, sting marks leaking juice and causing them to be full of worms around the pips. Maybe even my pears, also leaking juice and full of worms.

Can anybody please help with a cure to kill off these pests as I also have cucumber starting to bear and I dread that they should go there too.
Thank you, Harold. [email protected] +2782 869 0250