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How To Get Rid Of Gnats On Houseplants

by Madison Crabtree July 19, 2019

How To Get Rid Of Gnats On Houseplants

Have you noticed a lot of tiny flying pests in your house, especially in areas around your plants? Do they appear more frequently after you water those plants? Does it seem like every time you kill one, there are five more the next day? If you answered 'yes', bad news - you probably have a problem with fungus gnats or fruit flies.

 

Symptoms

Let’s take a look at how you can spot these pests. Check the foliage (or flowers), planter rim and soil for insects daily. Once you discover adults, eggs and larvae are usually already present in the soil. But what kind of bugs do you have?

 

gnats and fruit flies

Fungus gnats are between 1/16” and 1/8” long and have thin bodies, kind of like mosquitoes with grey or clear wings, black heads and slender legs. You can also identify them by their long, segmented antennae. Fruit flies are smaller and more compact, with stubbier legs, and are often slightly more orange. Luckily, treatments are the same for both. 

Where do they come from? Most commonly, they come in the soil of a newly purchased plant, in a bag of potting mix, or from an open window or plant that was brought in from outside.

 

Diagnosis

Fruit flies and fungus gnats feed on rotting organic debris in potting soil, so they’re a common problem for plant lovers. You might also find them in the kitchen, feeding on overripe fruits. While the hovering presence of adults are just plain annoying, the larvae can cause some serious damage to root systems, so you definitely don’t want to ignore them. The good news is that both pests only live for a few days, so all you have to do is interrupt their life cycle, and time will do the rest. Read on for prevention methods and treatments for getting rid of fungus gnats and fruit flies! 

 

Prevention

1. ADJUST YOUR WATERING HABITS

Pests like fruit flies and gnats are comfortable in damp dirt; eggs and larvae can’t survive without constant moist surroundings. Chances are, your plant can handle less water than you’re giving it, so try testing the soil with your finger and only watering when it’s completely dry at least 2 inches down. If you’re not great with gauging moisture by yourself, you can pick up a moisture sensor gauge that can stick right in your planter. Remember, overwatering is the #1 cause of houseplant deaths!

2. CONSIDER YOUR DRAINAGE & HUMIDITY

If your planter uses a tray underneath, empty that saucer immediately after watering to discourage the accumulation of moisture. If you’re using the Wally Eco, the perforated holes in the front of the basket helps the soil to aerate and evaporate excess moisture, but just be careful not to water too much. Move your plant out of the bathroom if it’s too humid, or run the humidifier a little less.

Soil comparison

(Image credit: Chris Postalwait)

3. USE THE RIGHT SOIL

The best soils contain slow-decaying organic materials like coconut chunks or fiber and charcoal. On the inorganic side, Perlite is a good ingredient as well. Use a well-draining soil that is slow to decay; the older the potting medium, the more attractive it is to pests. Since open potting soil bags can be a breeding ground for gnats, you can also try storing unused potting soil in a sealed container - bugs can’t survive without oxygen. Along with this, never reuse soil when you repot a plant; it’s better to have fresh soil every time.

4. PRUNE, PRUNE, PRUNE

Daily, trim dying or dead foliage off your plant, particularly in areas close to the soil line, and remove shed plant material from the soil’s surface as soon as you notice it. The less decaying organic material there is, the less food for flies and gnats there will be!

 

Treatments  

 

Pebbles in planters

 

1. SMOTHER THE SOIL

Because gnats and fruit flies lay their eggs in the top layer of soil, you can prevent their larvae from being able to climb out by spreading a layer of aquarium gravel or coarse sand over the top of the soil. Make sure to pack it in well. The larvae will die trapped beneath, and you should be pest-free within a day or so.

Bonus: it looks great, too - and not just with succulents and cacti!

2. MAKE YOUR OWN STICKY TRAP

Make a DIY sticky trap with a 3 x 5 index card, a highlighter, a wooden stick (paint stirrer or dowel rod) and petroleum jelly. First, color both sides of the card with the highlighter to make it attractive to the flies and gnats. Then, attach it to the stick or rod with glue or staples. Finally, coat both sides of the card with a thick layer of petroleum jelly, and stick that baby in your planter and wait for them to take the bait. Repeat as necessary until they’ve all been lured to their deaths.

3. MAKE YOUR OWN DROWNING TRAP

It’s easy to make a DIY trap with what you have in your fridge. Using apple cider vinegar mixed with fruit juice or beer, pour your liquid solution to about 1/4” from the bottom in a plastic cup. (Other kinds of vinegar or alcohol will work too.) Then add a drop of liquid dish soap and stir. If you want to speed up the process, you can also add a chunk of ripe fruit like banana or melon, making sure it protrudes above the liquid - it will attract pests faster than liquid alone. Using plastic wrap, cover the top of the cup and secure it with a rubber band, then poke some holes in it with a toothpick. Your trap is complete!

DIY fruit fly trap

(Image credit: Joe Lingeman)

All you have to do now is set it on a shelf or somewhere near your plant. They’re attracted to fermentation (to lay their eggs) and won’t be able to resist crawling in those holes and investigating the liquid. Once they touch down, even though they would normally be able to walk on top, the soap in the solution breaks the surface tension and prevents their escape, causing them to drown. When you’re done with the trap, just tape over the holes and dump it in the trash. Good riddance!

4. USE SPUD POWER

Got potatoes just lying around? Cut them up into small, 1/2” pieces and set several of them on the soil of your planter. Larvae will climb out of the soil to feed on them within a day or two. If you don’t see them on the chunks, check for holes and bite marks. Simply collect the pieces, seal them in a plastic bag and discard.

5. SANITIZE AND REPOT

Not willing to wait for them to take the bait, or the problem is simply too widespread? Gently remove your plant from its planter and remove as much soil as you can without disturbing its roots. Use a plastic bag to seal up the infected soil and DO NOT compost it. Then, thoroughly disinfect your planter using soap and hot water and repot your plant into fresh soil. Combine this method with any of the others to ensure that they don’t come buzzing back! In severe cases, you may have to do a full cleanse, including washing the roots.  

 

Carnivorous plant

 

6. PLANT CARNIVOROUS PLANTS

Looking for something more exotic as pest control? Pick up a carnivorous plant and let them feed!

7. USE A SPRAY BOTTLE 

If those pests just won't quit, you can use a solution of water and soap in a spray bottle to spray into the top layer of soil (or pour it directly on top). You can also do this with an organic insecticidal soap or Neem oil mixture; these natural pesticides should be effective after a few treatments. 

8. INDOOR PESTICIDES

When all else fails, a stronger approach may be necessary. You can visit a local garden store to pick up houseplant pesticides (make sure they're labeled for indoor use) that can be sprayed onto your plant. You may want to take it outside to treat it, and bring it back inside after it has dried completely. Your plant may show signs of pesticide damage, but generally these won't kill the plant. Check with your garden store or nursery if you're concerned! 

 

We hope these tips and tricks help you eradicate these flying nuisances once and for all! 

Pro Tip: If these methods aren’t working for you, it’s possible that you have gnats or flies breeding elsewhere. Try pouring boiling water down drains and toilets near where you see the pests, and make sure they are clear of debris that may catch moisture.

 

Employee Picks

 

Sticky tape  Bonide Systemic Houseplant Mosquito bits Diffuser
Houseplant Sticky Stakes Bonide Systemic Houseplant Insect Control Mosquito Bits Essential Oil Diffuser (use with lemongrass or peppermint)

 





Madison Crabtree
Madison Crabtree

Author



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