Fungus Gnats Infestation in Retail Compost Bags: A St Albans, Hertfordshire Problem?

Hello fellow gardeners,

I'm writing to bring attention to an issue I've encountered and to seek potential solutions. A few months ago, I purchased an all-purpose soil from Tesco for repotting my houseplants. Soon after, I noticed an infestation of fungus gnats in my home, traced back to the soil.

I managed to rid my home of the gnats by putting the affected plants outdoors. Recently, when I planned to purchase new compost, I observed fungus gnats surrounding the compost bags at several stores. These included two B&Qs, Morrisons supermarket, and Homebase, all within the St Albans, Hertfordshire area. It appeared as though every available compost bag was plagued with these pests, which deterred me from making a purchase.

Online research yielded no relevant results. I'm left wondering if this is a local problem or a larger, unreported issue. Could it be a shared supplier issue among these large retailers?

I'm interested in hearing if anyone else has encountered this problem. If you have, did you bring it to the attention of the store? Additionally, I'm seeking advice on where to buy gnat-free compost in or around St Albans.

I look forward to any advice or insight you may have, thanks in advance.

Best regards,

Ira

 

Another member on here steered me toward Mosquito Bits. It works.

 

Doubt it's restricted to St Albans; is it really a problem though. Fungus gnats and their maggots tend not to bother plants or healthy seedlings. They feed on fungus growing in the compost, numbers may have increased with the switch to peat free composts.
They are not a problem if the compost is kept on the drier side, I'd buy a bag of whatever was best value and then keep it outside in a shed, garage, car porch or similar.
If really concerned then see here Sciarid Fly Nematodes | Green Gardener

 

The increase in numbers is definitely down to the replacement of peat with wood waste in multi-purpose compost, so a nationwide (or even worldwide) problem. As a cheap, quick fix for sowings or houseplants, stick a few matches head side down in the pots. Replace after a couple of weeks if necessary. I tried the nematodes with conspicuous lack of success

 

Welcome Ira B.

Sciarid flies have been a problem in compost for at least a decade now Ira and it doesn't make any difference what you buy or where you buy it. Having battled with these annoying flies indoors for years I decided to give up on house plants. It had got to the point they were finding a way into my smoke alarms and setting them off - and also stopped two functioning completely.

Having said that, I do start a certain amount of seeds off indoors and grow them on until they can go outside. I cook the compost in the microwave for two minutes, allowing it to cool before using it and that seems to kill both the flies and their maggots. It's a long process but seems to work.

@noisette47 I found matches don't work.

 

Definitely water from the base so the top remains dry. Zap the compost in the microwave before using it as well.

 

Think you will find them in any bags of compost and though there are many different retail brands they probably only come from a couple of manufacturers.

Have tried several method to control them before, but for house plants and in the greenhouse have found that the Mosquito Bits that @CanadianLori mentions has worked best of all.

Not cheap, and only found them on Amazon, but a pack will dose hundeds of houseplants.
https://www.amazon.co.uk/Summit-res...&sprefix=mosquito+bits,outdoor,62&sr=1-4&th=1