Due to the method I use in my seed rasing I do tend to water them alot. The germinated pots are removed from the propagation after only 3 weeks and placed on the benching, in a shady spot and lightly watered daily.
I have only had the Scarid fly problem for the last few months, no problem at all last year, and the Carnivorous plants are helping to get it under contol. I have tried spraying but it doesn't seem to work, I think the life cycle of the fly is to short too for the chemical to have any real effect to work.
I have been pricking out the seedlings that are big enought to handle into fresh loam based compost, I do not use peat based composts for anything, being very careful to inspect each root for fly maggot. I am pricking out into polystrene trays then moving them to another part of the glasshouse.
Has regards Mealy.. you will never get rid of it once you've got it, all you can do is hope to control it. I use liquid Pravdo watered into the bottom of the tray so that the roots can take it up. I never water over head has some plants can burn on top no matter now careful you are.
I inspect the plants all the time by picking them up and looking. If I see any Mealy I use a tooth pick and then give them a spray with aerosol Pravdo and place the plant under the bench for a few days.