Question
Hi Will,

I have a question that is not directly related to house plants but it is about the gnats that are always buzzing around my indoor plants and lately, my head. I understand that they come from the soil and the infestation seems to be getting out of control. I'm not overwatering my plants by the way so the soil is not constantly wet. I'm wondering if there is a way to get rid of the gnats without harming my plants. Thank you for your help.

Answer
Hi Juliet,

Unfortunately, the fungus gnat problem you have IS directly related to your houseplants. The gnat larvae live in decaying organic matter - damp soil and rotting roots - where they feed and then as adults develop wings and fly out of the soil to lay eggs in other nearby plants.

Most of the larvae live in the top inch or two of soil so they are close to the surface. So the first step in control is to remove all loose soil not in direct contact with the roots. This loose soil serves no useful purpose and by discarding it, you will eliminate many of the larvae.

It is important to allow the soil to dry out as deep into the soil as possible - right to the wilt point. This drying down will deprive the larvae of the moisture they require to survive. Most houseplants can survive more dryness than people think.

After removing the excess soil from the surface, you can sprinkle a light layer of builders or river sand on the surface. The sharp edges of the sand grains will carve up the larvae as they try to move to the surface.

If you do all of the above, it should not be necessary to use any pesticides. The winged adults will die back on their own accord after about a week, their normal lifespan. The number of larvae will gradually diminish and so will the flying gnat population.

Where did the gnats come from? They may have been in the soil when you purchased the plant, but more often they are introduced when plants are repotted with packaged potting mixes that are not sufficiently sterile. Miracle-Gro potting mixes generate a lot of complaints about fungus gnats.

I have written an article on indoor plant pests, including fungus gnats, that I will email for free to you (or anyone else) who sends a request to me at [email protected].

Please let me know if any of this is unclear or if you have any additional questions.

If this information has been helpful, please click the Rate Volunteer bar below and enter a rating and nomination for me. I am a volunteer on this site so Ratings are the only compensation I receive for answering plant questions.

Need more information? Visit my website at:
A link to PlantCareExperts.com

or email me at [email protected] or call me at 917-887-8601 (EST)
 
Regards,
Will Creed, Interior Landscaper
Horticultural Help, NYC

Visit my website at: A link to PlantCareExperts.com