white maggots Dead Courgettes and sick beans

[KellsSimon]

Hi all,
Had some courgette plants in the ground doing ok, but after a while two stopped growing, then started to look off, yellowish leaves etc, then went limp, and eventually i got sick of looking at them and dug them up for a look underneath to see if anything had been munching the roots.
I found that the roots had all been eaten back into the peatpots they had germinated and been planted out in.
Right at the top of the plant where the stem joins the roots it was all dead and dried up and just above this, inside the crown of the courgette plant these little maggoty worms were busy munching away.
They have eaten their way up the roots and burrowed inside the plant!
Real nasty!
At first i though they might be vine weevle larve, but i think they are too small. as they are only 5mm long max and the head is pointed rather than flat and black/brown.
The compost they were planted in was new, as was the raised bed they went into, having previousley been slabbed over...though the soil was the soil that had always been their
I also dug up some dwarf french beans that had also slowed down, and found the grubs there. As these beans were still possessed of some roots, i washed off the soil and bugs (squishing as many as possible) and replanted.
They have two choices.
Does any one know what this bug is?
how do i kill it,
If there was a theoretical path nearby that needed cleaning would Armillartox have any negative effects on food crops or is it safe to use on crops,
sorry 'edible path...'
I would really appreciate any help on this, as having things being killed all over the place and eaten alive is too depressing, and i was the one who was going to eat them!
cheers

[sewer rat]

They coud be the larvae of the scariad fly - the desription fits and the damage to your plants also sounds as if it could be them.
Put Scariad Fly larva into google and see what ya think. Let us know if this is what they are, if not, come back to me and I'll have another think

[Two_Sheds]

It could be Sciarid Fly larvae, if you've been over-watering? You should not water seedlings from the top either, but put the pots into a tray of water instead.
"The fungus gnat, or scariad fly, is in itself not a problem. You will see the tiny black flies walking across the top of the compost, mainly of pot plants, fluttering their tiny wings. Although they are unsightly and can be a nuisance when numbers build up it is the larvae, the tiny almost transparent maggots that do the damage.
They feed on dead and decaying matter in the soil, along with tiny roots. This can be a problem with cuttings or seeds, but rarely causes any problems to established plants. Make sure that the compost is not overwatered"

[KellsSimon]

Sciarid fly larva looks like it is the culprit.
Horticultural Development Company is the defra site with pictures of them.
The annoying thig is that the plants only got it (or displayed symptoms) after being in the ground for 2 / 3 weeks, though that is within the time scale of egg to larve if they had been infected when out in the open.
The plants were still young, but had put out roots into the surrounding soil and started to grow, so how long does it take to become 'established' is it just about having enough roots to afford to loose some to the larvae?
other thing is the soluion, what do you think about the Armillartox idea?
if you have any better ideas i'd really like to know as the idea of a chemical 'final solution'.... doesn't really appeal