Things that have been attacking my veg.

[lolie]

Whitefly leave a sticky residue and I am wondering if this helps to create the black mould.

Indeed it does.

Whitefly also excrete honeydew which can lead to infestations of sooty mould, a fungal disease that looks like black charcoal on the leaf. The saliva of the silverleaf whitefly contains a toxin that may cause further damage to the plant.

Controlling whitefly | Sustainable Gardening Australia

A lot of the damage whitefly do is indirect. They spread an awful lot of diseases in the garden.