sciarid flies killing my seedlings?!

[bigpepperplant]

I've got loads of little black flies hopping around the surface of the compost on my germinating lettuce, pak choi and chilli seedlings. I think they must have come in on a tarragon I'm overwintering on the kitchen windowsill. I wasn't too bothered about them, but yesterday all my pak choi seedlings suddenly keeled over and died as did the lettuce. I can't understand why - I don't think it's damping off because they're not rotting at the base, and wondered if it might be a cold draught from the window. However, since then I've found a few white maggots in the compost and assume these are sciarid fly maggot.

I've put the dead seedlings outside to try to get the flies out of the house, but have 3 trays of chillis just about to germinate (I hope) and there are still black flies (they look like fruit flies, but having researched a bit on the internet, I reckon they're sciarid flies) hopping around all over them. I just found a maggot in one of them this morning. Does anyone have any advice as to how I can deal with these horrors? Or should I just give up, put everything outside to kill the pests and start again with new compost in a couple of weeks?

[glallotments]

Must admit I Think trying to keep seedlings going at the moment is a hard task which is why we don't sow til much later but we are much further north.

[PLUMPUDDING]

The yellow sticky traps placed near to your seedlings should catch quite a few, and perhaps your compost is a bit on the wet side, which does seem to attract them. Good luck.

[bigpepperplant]

An update - I ended up ditching all the seeds since they were being eaten by these little maggots. I think they'd been brought in old compost that had been opened since last year - a bit of a lesson in not using old compost for seed sowing.

[John]

Hello BPP
I've found that a whiff of kitchen fly-killer aerosol will often do the trick in getting rid of this sort of pest. You might need to repeat over a few days. Its best used in the late evening as the spray rapidly loses its effectiveness in bright light.

John

[sarahscottdavies]

Hiya.
I start most my seedlings in the house on windowsills late winter/early spring and this year we are plagued with the wretched things, and they killed off my dwarf french beans that were happily over wintering in the kitchen that were just starting to flower.
Sticky fly paper does seem to help control their numbers a little. I once read that if you sterilise your potting compost before use by putting a bit at a time on high power in the microwave for a few minutes, this will kill outright anything lurking in the soil that shouldn't be there....however, I was wondering, would this some how destroy the nutrients in the soil, (as they reckon microwaving fruit and veg helps to destroy a lot of vitamins and minerals)?

[Johnboy]

Strange as it may seem a lighted candle over night put in a safe place close to your plants is a very good method of controlling Sciarid Flies.
If you see any shots of a forced Rhubarb Crop they always have candles alight and I suspect it is to control these little buggers!
JB.

[John Walker]

Candles are used as an integral part of growing a forced rhubarb crop:

The candles do more than guide the pickers’ path. Once inside the dark sheds, where the rhubarb is kept at a temperature of 13C, the naked flames perform a clever trick. Each stalk of rhubarb, after two weeks in the pitch black environment, is desperate to glimpse even the faintest spot of light. On the promise of candlelight, the stalks force their way up out of their earthy nest.

Full article: http://www.lovefood.com/guide/producers ... andlelight

The rhubarb growers I've visited have never mentioned problems with sciarid flies (the forced crop being grown dark and cool is probably a big factor).

For an earth-friendly and non-chemical means of controlling sciarid fly you can introduce the predatory mite Hypoaspis miles, a natural biological control which eats the sciarid fly grubs. Google 'sciarid fly control' for numerous mail order suppliers.

[Johnboy]

John Walker.
I think you will find that candles serve a dual purpose and it may not be Sciarid flies but other flying pest that will be attracted by light and destroyed when they fly through the flame.
Mushroom growers use candles against Sciarid flies and other flying pests.
If it were just light they were after they would use electricity instead of expensive candles. Just think about it a little before you reply.
And I would like a reply.
JB.

[alan refail]

For an earth-friendly and non-chemical means of controlling sciarid fly you can introduce the predatory mite Hypoaspis miles, a natural biological control which eats the sciarid fly grubs. Google 'sciarid fly control' for numerous mail order suppliers.

At £37 plus £5.95 p and p it's damned pricey as well as "earth-friendly".

http://www.aquaculture-hydroponics.co.u ... goryID=282

[alan refail]

Hiya.
I start most my seedlings in the house on windowsills late winter/early spring and this year we are plagued with the wretched things, and they killed off my dwarf french beans that were happily over wintering in the kitchen that were just starting to flower.

Hi Sarah

I am intrigued by the idea of overwintered French beans flowering in the kitchen on the 1 March. When did you sow them? Was your intention to keep them inside until cropping? How do they grow in the low light levels of winter?

[Johnboy]

Hi BPP,
I would ask you to simply try the candle method and see if it helps.If it does help you perhaps you might come back and tell us all. Or come to think of it should it not work come back and tell us also..
They are a real nuisance. But £37.00 plus £5.95 seems an awful lot to pay
far too much in my opinion. Probably by the time you were to receive the biological control the damage would already have been done.
JB.

[John Walker]

@Johnboy

I give all my comments plenty of thought before I post them.

Candles are used in rhubarb forcing sheds precisely because they give off just the amount and quality of light to coax the sticks gently into growth without turning them green, and just enough illumination for the harvesters to work by. They do not use any other lights - including electric - because it spoils the colour. The candles are not used for controlling sciarid fly. In fact I saw no bugs when I visited (and interviewed in considerable depth) a commercial grower in Yorkshire's 'rhubarb triangle'. The rhubarb crowns are also washed clean of soil so there is very little organic matter present which would even attract sciarids (or much else).

It's different in commercial mushroom production where the mushrooms are grown (in constant darkness) on a substrate that's rich in decaying organic matter, which naturally attracts pests such as sciarid.

It's probably worth giving the candle technique a try, but it's hard to see how it's going to be effective during daylight hours (or how it will control the larvae), whereas a biological control agent like Hypoaspis is busy controlling the pest 24/7 (eating sciarid eggs and larvae).

@alan refail

I agree the price can appear steep but sometimes you just have to put your money where your earth-friendly values and convictions are.

Anyway, you don't need to pay over forty quid for Hypoaspis. Ladybird Plant Care offer it in packs of 10,000 for £16.95 inc p&p to treat 50 square metres. It pays to shop around.

http://ladybirdplantcare.co.uk/hypoaspis.html

I overlooked to mention before that there is also a nematode (Steinernema feltiae) available that controls sciarid fly larvae. You simply mix it with water and then apply it to pots, containers or soil beds of affected plants - and any others which might be vulnerable. The microscopic nematodes kill any larvae in the compost so it's a very effective means of keeping them in check. Like Hypoaspis, the nematodes are safe to use and environmentally benign.

Nemasys supply a pack of mixed nematodes (packaged as their 'Grow Your Own', which also controls pests such as carrot and cabbage root fly and caterpillars) which treats 60 square metres. Orders are usually despatched within a few days of ordering (as are the predatory mite Hypoaspis) so its worth ordering the moment you spot any adult flies. Harrod Horticultural offer single packs of Nemasys'Grow Your Own' for £6.95 inc p&p with availability starting this month.

http://www.nemasysinfo.com/gyo.shtmll
http://www.harrodhorticultural.com/Harr ... tionAnchor

[Johnboy]

John Walker,
I thank you for your reply. Although Rhubarb for forcing may be free of
soil, maggots of various pests, live in the roots and not the soil.
However I accept that you explanation may well be correct.
What gardeners are after are simple cost effective solutions and although I appreciate that a candle during daylight hours is simply a candle but flies are attracted by light and if a candle is left alight in the darkness it will have some form of control. To suggest that a biological treatment, which is really meant for commercial outlets, at a price no simple gardener would pay to get rid of Sciarid fly on a window sill is informative but rather impractical.
Sadly it looks like BPP having to resow and start again. Perhaps the offending plant can be placed in a dark place with a lighted candle a very good measure of control may be achieved.
JB.

[sarahscottdavies]

I planted my dwarf french beans in deep pots on warm windowsill, think it was early december although i don't really remember exactly but it was definitely winter, dark and freezing! They were doing brilliantly, and didn't seem to be at all bothered by dark short days, so long as they were warm..planted 3 to each pot and had 5 pots. It was just an experiment really to see which of more tender crops could be grown indoors through winter, (as well as more hardy crops in my greenhouse). One even had miny beans forming until the flies got the better of them, (and my husbands patience!!!) Also tried courgettes, the pathenocarpic variey (as too were the dwarf beans). They have done brill and are flowering already (they are in buckets on another windowsill and yes i have very large windowsills!!). Hopefully they can go out in greenhouse in april and fingers crossed for very early courgettes until my main sowings get underway. (The flies are on these too but courgette plants must be tough as old boots and don't seem to be bothered by them and we've reduced their numbers by lots of sticky fly paper hanging over them.) I'm very much enjoying the experiment.