It’s easy to assume that venus fly traps pretty much everything that flutters their way – in many cases, people set up these carnivorous beauties to help protect other nearby houseplants. But do venus fly traps eat fungus gnats?
The answer is yes – venus fly traps do eat fungus gnats, but at the same time, gnats can eat away at a venus fly trap’s roots!
Keep reading, and I’ll take you through this slightly complex relationship, and how you can keep your own venus fly trap in tip-top condition away from nuisance gnats.
What is a venus fly trap?
The clue is in the name! venus fly traps do us a huge favour by trapping and devouring undesirable pests. They make attractive plants, too – with fascinating mobility – they have jaw-like leaves that clasp together! This movement creates the trap from which the plant is named.
How do venus fly traps ‘work’?
Venus fly trap mechanisms are pretty sensitive, too. Sensory cells along their hair-like bristles signal when prey is in the vicinity of the trap. As insects touch these nerve cells, they stimulate a sensory action, resulting in leaves closing in on the captured prey.
The plant’s sharp, fine needles are at the edges of each pair of leaves. These leaves behave as jaws, and the sharp bristles are brought together like teeth. It’s really fascinating to watch – and if a fungus gnat dares get too close, it’s likely to get snapped up pretty quick…
Can anything else trigger venus fly traps?
Yes – in fact, many plant parents try and set venus fly traps off on their own! Fancy ‘testing out’ your fly trap without getting your fingers nibbled?
Simply take a cotton bud or even the thin stalk of a plant, and very gently touch the inner part of the leaves. Remember – any fungus gnats that venus fly traps want to eat will move slowly and weigh barely anything.
Make sure to touch the leaf very gently and take your time. If your experiment works, a pair of leaves will clasp together. Watch carefully and be prepared to withdraw your probe gently. This will help you avoid damaging your plant.
Now we know how venus fly traps work, let’s take a look at our nemesis of the day, the fungus gnat.
What are fungus gnats?
fungus gnats are, simply put, common winged pests. They can infest soil, decompose organic matter, and even potting mix. They require moisture to thrive.
Within the home, leaking appliances and pipes can sometimes provide a comfortable home for them. Humid kitchens, bathrooms and shower rooms provide great living conditions for these pests. They’re frequently mistaken for other tiny winged pests such as fruit flies, too.
It’s easy to understand how overwatering your plants do fungus gnats a great favour – you are inviting them to enjoy the moisture levels they love! You are also inadvertently causing roots to become soggy as plant containers become saturated – just another reason why a firm watering schedule is so important.
Are fungus gnats harmful?
Fungus gnats aren’t harmful to humans, but they will happily munch away at plant leaves and roots if left to thrive. That does include your venus fly trap, too – meaning while you may set up a fly trap to eat gnats, the gnats could be eating away at your plant!
Why are venus fly traps ideal for handling fungus gnats?
Fungus gnats breed very quickly, meaning you could soon have an infestation on your hands before you know it. However, a venus fly trap can help to swallow up some of the more persistent pests in your home – though you shouldn’t rely on them completely to remove the pests on-sight.
Venus fly traps are great at catching insects but aren’t always effective at keeping smaller pests in place. Therefore, while fly trap leaves can snap shut and keep bigger bugs enclosed, smaller beasties like gnats may find their way out fairly easily.
It’s also worth noting that venus fly traps don’t always grow that many leaf traps in the first place. The maximum you’ll grow on any given plant is around ten, which if you have a major infestation, isn’t always going to be great for keeping populations low.
You’ll also need to be careful when you grow your venus fly traps. If you’re expecting your traps to take care of fungus gnats during the winter, for example, you can forget about it. Venus fly traps will typically sit dormant during colder months, which is also when they will start dropping leaves – and normally won’t eat pests, either.
While these points are worth bearing in mind, having a few venus fly traps in a row can help to rescue insect numbers – such as fungus gnats – if you have a commonly recurring or particularly stubborn infestation.
How long does it take a venus fly trap to devour a fungus gnat?
Well, in this respect, size matters! venus fly traps can capture and devour up to a small handful of fungus gnats per month.
Of course, some venus fly traps have more operational traps than others, which also vary in size. On an individual basis, a captive gnat may disappear within three days. Once the leaves are openly apart, the plant is ready for its next victim!
Do take this with a pinch of salt. It can take up to two weeks for venus fly traps to finish digesting their prey, and during this time, their traps will stay shut. That means any more gnats breeding around your home will have free reign to go undisturbed.
Why does trap size matter when catching fungus gnats?
Smaller traps can be more actively engaged in trapping fungus gnats than their larger neighbouring traps.
If you study the size of the fungus gnats visiting your plant, it’s likely they’ll range in length. From between a large half-inch in length to a much smaller 1/32 of an inch, fungus gnats have long, slender bodies.
This weight distribution means their agile legs share the load and assist their balance. It also means that, proportionally, a fly trap’s sensory cells may only receive a signal from one or two limbs at a time as a creature explores a cavernous trap.
The larger leaves may not register the exploring gnat if it is on the small side. Using a magnifying glass, you may even see small fungus gnats escaping out of larger venus fly traps! For this reason, smaller traps with finer sensors may be more successful as predators.
How do fungus gnats harm venus fly traps?
Fungus gnats can, as with most plants, breed and eat away at root matter, causing your venus traps to slowly wither and die. Therefore, even if you have venus fly traps set up to catch gnats, there’s every chance the pests will already be damaging the plants themselves.
A simple way to reduce the number of fungus gnats is to carefully check your venus fly trap for any rotting leaves or roots. If you get into the habit of doing this routinely, not only will you better ensure the overall health of your plant but also monitor it regularly for unwanted guests!
A mild solution of apple cider vinegar applied to the surface of your growth medium can reduce the number of fungus gnats preying on your venus fly traps. To attract these pests away from other surfaces, consider setting up yellow flypaper or sticky traps – which are cheap and easy enough to come by online.
What other plants help kill fungus gnats?
Venus fly traps aren’t the only natural specimens that can help reduce fungus gnat populations. Here are some other houseplants you may wish to grow alongside.
Sundews are bright-coloured carnivorous plants that tend to be fairly easy to grow. What’s more, there are multiple varieties of this plant that fare well as indoor specimens. Unlike venus fly traps, too, there are some variations of the sundew that won’t need to go dormant in the winter months.
However, sundews – while great at helping to reduce bug populations – can be quite small compared to venus fly traps. They’ll also need a regular supply of pests to stay healthy.
Dewy pines (Drosophyllum lusitanicum)
You won’t see dewy pines too often unless you live in Spain or Portugal – but get lucky enough to take one home, and you’ll have one of the best-undisputed fungus gnat killers of the natural world in your arsenal.
This is a super-sticky plant that simply traps pests if they dare to land on its leaves. Fungus gnats won’t go anywhere fast if they stop on a dewy pine for a rest. They can be a little tricky to look after, but given they thrive in desert conditions, they’re not too picky about water.
Tropical pitcher plants (Nepenthes)
The nepenthes is a fairly crafty plant in that it will attract fungus gnats with the promise of a sweet treat, only to snare it inside its pitcher. Here, the plant will start digesting any bugs that fall in.
The nepenthes is one of the best natural bug catchers as it’ll hold waves of flies at any one time. However, you’ll need to look after them carefully so that it grows pitchers large enough to handle your bug problem!
While they may sound pleasant, butterworts are highly carnivorous plants that insects really won’t want to get on the wrong side of! They have sticky leaves, meaning that once a fungus gnat lands on this plant, it’s going nowhere.
That said, it’s pretty rare you’ll find a butterwort to grow at home, though it’s not unheard of. They won’t go into dormancy and act as natural flypaper across the year. If you’re willing to hunt around for this specimen, it’s a fantastic support against a variety of flying critters.
Trumpet pitchers (Sarracenia)
Sarracenias are similar to nepenthes in that they have pitchers that are great for capturing fungus gnats over time. They tend to work best as outdoor pest catchers, however, as they grow fairly large and won’t fare too well with indirect sunlight.
If you’re up to the challenge of growing a sarracenia indoors, they’re ideal for ensnaring multiple fungus gnats at once, particularly as their pitchers can grow to an indefinite size. However, it’s probably best leaving this plant outside.
Should I get a venus fly trap to deal with fungus gnats?
As it stands, there are options that are a little more reliable than venus fly traps alone for dealing with fungus gnats. While they’re great for dealing with smaller swarms of these pests, they do stay dormant for long periods and aren’t always going to keep minibeasts sealed in for long.
Therefore, I’d personally recommend you try and set up a few traps for gnats if they’re proving a regular nuisance. For example, alongside venus fly traps, consider setting up some of the alternative carnivorous plants listed above. Do also invest in fly paper and luminous traps, too, great for attracting pests and keeping them stuck.
For all venus fly traps have a great collective reputation for being natural pest controllers, they’re worth setting up at home just to keep your home looking bright and exotic!
Venus fly traps are great talking points, even if they may not always do the best job at keeping your fungus gnat populations down. Consider setting up highly fragrant herbs such as rosemary and lavender alongside your venus fly traps to really keep the gnats at bay. Take a look at our guide to getting rid of houseplant flies for further details