Friday, April 03, 2009

Fair advice for getting rid of fungus gnats

Most of you seem to have seen through my April Fools joke about gene manipulated killer slugs and extra tiny sheep (I've always thought someone should breed minisheep for minicollies). It wasn't a joke taken from nowhere though - there was a company at the Nordic Gardens fair that did bring live animals to their booths.

Biobasiq Sverige AB (link in swedish and danish...) is a swedish company selling biological control and beneficial insects to professional and hobby gardeners. We amateurs are not spoiled with these things, I can tell you, and I was even more charmed by the bumble bee nest they had brought to their booth. I didn't know you can hold bumble bees similar to the way you keep bees. You won't get honey but the bumble bees are sturdy pollinators that braves colder weather than bees and they are not as 'stinger happy' as them. But I have to admit I my prime interest was the fungus gnat killer nematodes they sell in small units (previously I've only found them in megapacks for proffessional food growers). Fungus gnats are the most common pest indoors, and almost impossible to get rid of.

In short the nematodes are parasites infecting the fungus gnat worms in the soil, which means they die before they can evolve into a gnat (or eat more tender roots). They are delivered in a plastic box with a granulate and are meant to be mixed into water and watered out into the soil. What you need to know is that this is something to be used fresh, so you can't stock up on them. The best thing is to use the stuff as soon as it arrives to your home.

A more traditional way to fight fungus gnats is to use fly paper. I bought ten pieces at the Willab Garden booth (link in swedish only). Willab Garden sells greenhouses and had brought a shop with bits and bobs for keeping the content of them fresh to the fair. It's worth noting that green house gardening is what comes closest to indoor vegetable gardening, which makes it worth checking out green house tips and -shops for advice and useful tools - in many cases this is more rewarding than checking out traditional indoor gardening resources.

As you can see on the picture I've cut the fly papers into smaller pieces. After surveying my plants I realised it would be more effective letting every container have a paper on its own to catch an optimal amount of gnats. (They've eaten my lovely scallions - it's WAR! Again.) It has worked out well, and I get a hint about where the problem is most serious. But the glue was STICKY! The scissors clogged up, and with my fingers sticking to everything I felt like Peter Parker when he discovers he have spider forces. Fortunately I could remove it with vegetable oil (a household trick I learned from my grandfather who used to work in a sawmill; resin is best removed with butter, so whenever I fail to clean off glue with soap I try some kind of common household fat).

[Fridays is usually the day I let you peek into my green book - but it's disappeared. I'm panicking a bit, but I hope I'll find it again.]


Kenneth Moore said...

Oh man, I hope the gnats go away... From what I've read, they aren't too much of an issue for the plants--they only eat the plants if there are other problems that aren't being dealt with (overwatering or whatnot).

Since I stopped buying bags of horrible horrible potting soil and pesticided with Neem, I haven't had any gnats ::crosses fingers::.

But I just ran across some sources of such nematodes in the US, which might be good for your non-European readers!

Planet Natural's Nematodes

$31 or so, "free" shipping (included in price, likely, on the basis of comparison shopping for another product sold by this company), but you're right, it's a LOT of product for an indoor gardener--I would only need 1/20 of it, maybe less.

HIrt's Garden Nematodes

Home Despot Nematodes

Cheaper (about $20 per unit) at these places, but unknown quantities (1 lb? 7 million nematodes?) and shipping prices.

Rosengeranium said...

Great! Thanks!

vegged said...

Those nematodes are amazing. They'll decimate fungus gnats. I've used them when fly strips don't solve the problem.

But I started treating my plants with Scorpion Juice and haven't had any problem with gnats since.

MrBrownThumb said...

hope the pest problem gets resolved. But you can use the opportunity to sneak in a couple of carnivorous plants to tackle the houseplant pests.

Rosengeranium said...

Vegged: "Scorpion Juice" now that's a name that triggers the imagination. I did some online research since the product is not available in Sweden. I like the idea behind (strengthen the plants' immune system) and I'll take a look to see if I can get a general idea about the contents.

Mr Brown Thumb: I've thought of it many times - I think you actually gave me the idea. The only thing that stops me is that I'm short of space.