[karooba007]

I have an indoor black fly infestation. They have layed eggs in the pots containing the squashes. the larvae are drilling into the stems of the squash plants and as a result the plants die.
so far I have lost 4 squashes. Apart from not watering too much and removing the compost from around the stem of the squashes is there anything else I can do?
Been looking after these plants for two months so I really don't want to loose them.

[paintedlady]

when you say black fly, do you mean the aphid variety, or the little fruit flies that flit about the compost?  Aphids can be easily dealt with - spray the plants with dilute soapy water (the spray itself might knock them off, and the detergent kills them)  If the infestation is bad, you might have to do a second treatment.  I've never had problems with fruit flies before, and I can't think what else it could be - hopefully someone else might know & can advise.

[karooba007]

the tiny ones that are around the compost.

[paintedlady]

I've never had a problem with them before - they are more of a nuisance than a pest.

[karooba007]

yeah, neither did I until my plants started to look sick. I checked the base of the plants and found that the larvae had drilled into the base of the stem and were moving up the stem.
you live and learn.

[jb]

Bad news, it sounds like a severe sciarid fly infestation. These look just like fruit flies or fugnus gnats but are a real problem indoors as the larvae (small thin white) eat seedling roots. The really bad news is that if they are attacking the aerial parts it sugests that they are running out of roots to eat which would lead to your plants looking sick.
They were the bane of my life when I worked in a lab where they could destroy whole growth rooms of seedlings. They could be controlled by a chemical drench of the soil (sorry can't remember what) but whether this is appropriate for food crops I couldn't say. If you  google sciarid sites also suggest that some biological controls are effective but I'd also resow some back up seeds in case its too late for your current squashes.
Sorry for being the bearer of bad news 

[karooba007]

Yes it’s the fly u described. They ate my sweet pepers seeds as well. Maybe they are the reason my tomato seeds failed. So they are eating the roots as well, damn. I think I better get these plants planted outside quick and maybe their number will come down due to some other insect eating them. I have a lot of squash plants.
These flies arrived with some compost I bought.

[jb]

These flies arrived with some compost I bought.

Yes, that's where we got ours from.

Could be cured by sterilising the compost, although this also affects the balance of micro-organisms in the mix.  Try a good blast in the microwave but do it when everyone else is out and open all the windows as it will absolutly stink.
It might also be worth starting any seedlings off in vermiculite or vermiculite/perlite as that is guaranteed nasty free and while I've never tried it a fleece cover (held onto the sides of the pot by a rubber band should stop any residual flies getting in to lay more eggs. The key is to get the plant to a reasonable size as older plants seem to cope with attacks quite easily.
Good luck

[paintedlady]

These flies arrived with some compost I bought.

  that's awful - no wonder you've been having problems.  Would it be appropriate to ask whose compost it was so that others can avoid it, or is this a common fly that can infect compost generally?  With the amount of sowing I do at home, I couldn't possibly microwave all the compost I need 

[jb]

These flies arrived with some compost I bought.

  that's awful - no wonder you've been having problems.  Would it be appropriate to ask whose compost it was so that others can avoid it, or is this a common fly that can infect compost generally?  With the amount of sowing I do at home, I couldn't possibly microwave all the compost I need 

Probably highly inappropriate to single out one compost manufacturer as these flies occur naturally and they could easily sneak in and establish themselves and believe me, once established in a closed system (like indoors) they are a nightmare  to eradicate. Sadly I think this a case of bad luck as if any compost manufaturer routinely had infestations of sciarid they would soon go out of business as any seedlings in the compost would be destroyed  so that in effect the compost would be useless. Plus remember many composts are variable batch-to-batch so just because one batch is affected doesn't mean another one is (or another manufaturor may not carry them).

[karooba007]

I bought the infested bag of compost a year ago. I don't remember the name.  I used it for some indoor sowings for indoor plants. Didn’t think the small flies were a big deal, just a nuisance. Only now do I realise that the larvae are destroying my squash plants. I found out that they are also eating the base of the beetroot stems I have sowed ad well. They are also eating some of the seeds. I have been chasing flies and squashing them all weekend. Some plants are ok as they haven’t laid eggs in all the cells in the trays. Going to look for some chemical to kill the larvae.