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Fungus gnat infestation: What helps against the plant pests

6.3.2020

Translation: machine translated

Although the small midges only live for five days, as larvae they cause enough damage to your houseplants. There are some remedies that are supposed to help against them. But which ones are really effective?

We have a few new plants in the office. Unfortunately, fungus gnats were supplied free of charge. From one day to the next, dozens of gnats danced across the potting compost. Every now and then one gets lost near the head. This is annoying, but not harmful. What is harmful, however, are the larvae in the soil - at least for the houseplants. This is because the creatures feed on the roots and therefore need to be removed.

Thirsty route

These pests with dark-coloured wings (hence the name) often hide unnoticed in the potting soil. If this is watered regularly and kept moist, the midges multiply at lightning speed. So our first impulse is to stop watering. The soil is now dry, which is certainly not detrimental to the endeavour. But even after days, the midges are still not gone.

In the depths of the internet, I read that the sulphur from matches is supposed to kill the larvae. To do this, the matches are not lit and are stuck head first into the ground. But even this procedure has not visibly reduced the population. Heating the soil in the oven or microwave kills the pests. But so do all other living creatures and I would have to repot the plant for this method. I don't want to do that (yet), so I have to find another solution. I have therefore ordered Solbac from the shop. The biological preparation reaches the larvae's intestinal tract via the water and is said to lead to death within 24 hours if the toxin is sufficiently absorbed.

Andermatt Biogarten Solbac tabs (Fungus gnats)

Pesticide

CHF14.80 CHF98.66/1l

Andermatt Biogarten Solbac tabs

Fungus gnats

Biological weapons

I added one Solbac tablet per litre of water and then watered as normal. Then it's a case of waiting and letting the product do its work, as a visible change only occurs after about ten days. As soon as this period has elapsed, you will of course receive a brief update on the status. If the fungus gnat population is still as high as before, I will have to repeat the procedure. Otherwise, the mosquito plague is considered to have been defeated for the time being. To keep it that way, you can practise prophylaxis.

After the tablet has disintegrated, stir well and water the plant with it.

Don't overwater your plants. Especially in winter, many plants slow down their growth and therefore need less water. A layer of sand or gravel over the soil helps prevent fungus gnat attacks from the outside. This is because the insects only lay their larvae on the soil. A colleague also recommends vegan soil. Since he has been using the variant without animal compost, he has not had any more larvae. This is not proven, but perhaps worth a try. Coconut fibre soil is pest and weed-free. It also retains water well and the roots are well aerated. You will need to provide extra nutrients for this, as these are in short supply in coco soil.

Dennerle Crystal quartz gravel (Pyrites, other buildings)

Aquarium decoration

CHF27.–

Dennerle Crystal quartz gravel

Pyrites, other buildings

Potting soil

Quantity discount

CHF10.20 per piece for 2 units CHF1.02/1l

Siena Garden Coco-Earth

10 l

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Carolin Teufelberger

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carolin.teufelberger@digitecgalaxus.ch

My life in a nutshell? On a quest to broaden my horizon. I love discovering and learning new skills and I see a chance to experience something new in everything – be it travelling, reading, cooking, movies or DIY.

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