While talking with a friend about indoor plants, we got on the topic of bugs. “Those tiny black flies that buzz around my face while I’m working on the computer? They’re driving me crazy!”
You might’ve experienced them, too. They buzz around your face when you’re eating dinner or, like my friend, when you’re working on the computer. It’s irritating, like dogs that bark late at night or finding an empty toilet paper roll at an inopportune time.
These itty-bitty flies are called fungus gnats. They’re the size of sesame seeds and they eat eat like pigs. (I’ll explain shortly).
‘Fungus gnat’ is not a pretty name, but it fits, because they live and graze, quite contentedly, in the soil of indoor plants.
[Hi, there. This article you’re reading was originally published in the Kodiak Daily Mirror, the hometown newspaper for Kodiak, Alaska. You can access the archive page for my past columns, written each week since 1986].
The flying insects, the critters you’re most likely to meet, are the adult and final stage of a 3-week life cycle. Are you ready for a little biology?
Let’s start at the larval–little worm–stage, which takes place in the soil where they chomp on root hairs and decaying organic material. Don’t lose sleep over fungus gnats, though. They are more of a nuisance than trouble. But if left alone to breed to their hearts’ content, they can kill a plant.
If you suspect that fungus gnats have set up camp in your plants, here are three solutions:
1. Be a pest
Two can play this game. The object is to make life uncomfortable for the little guys by allowing the soil to dry out between waterings. Fungus gnats thrive on damp, decaying matter, so a parched desert-type environment is not where they want to raise a family.
2. Make a spray
Soap and Water Sprays
For soap sprays, you have 2 options: Buy commercial sprays, such as Safer products, or you can mix your own. (TIP: Where the recipe calls for liquid soap, as a general rule, hand and body soaps tend to be safer for plants).
If you’re new to these kinds of sprays, experiment by spraying some plants and not others. Be a careful observer of your plants’ response and please let me know how these recipes work for you.
Aphid Soap Spray
Ideal for all soft-bodied insects…
Easy recipe: Add 1 tablespoon of liquid soap (Dr. Bronner’s), which also works as an emulsifier to 4 cups of lukewarm water
Fill sprayer, gently invert a few times (try not to foam it up by shaking) and spray on affected plant leaves and stems, especially UNDER leaves and other hiding places where aphids hang out (hide).
TIP: To keep aphids from hanging out in the first place, increase air circulation around plants.
Store spray at room temperature. Note: The active ingredient in insecticidal soap comes from the fatty acids in animal fat or vegetable oil, so it’s important to use the real thing. As reported in the San Francisco Gate, the granddaughter of the company’s founder, Lisa Bronner:
Add 1/2 teaspoon of cinnamon or cayenne pepper to your aphid soap spray to deter future infestations. — Lisa Bronner
Willow Water Spray
For centuries, willow bark has been used to relieve pain and fever. Then in the early 1800s, the effective ingredient, salicin, was isolated from the bark. The hormones in willow also cause rapid rooting of plants. Later the Bayer Co. in Germany trademarked a stable form of acetylsalicylic acid, calling it aspirin.
Another discovery: In 2005 I came across a reference in The Avant Gardener newsletter whereby gardeners were reporting all sorts of plants growing remarkably better when given regular doses of aspirin water. Plants make salicylic acid to trigger natural defenses against bacteria, fungi, and viruses.
Aspirin, it turns out, is an activator of System Acquired Resistance (SAR). When stressed by drought, transplant shock, attacks by microbes, and so on, plants often don’t produce enough SAR to prevent injury. Long story short: Several species of willow thrive along Kodiak’s streams and other damp environments. Here’s how to make your own willow water:
How to make willow water
- Collect 2-3 cups of young willow twigs, pencil-thin or smaller. Remove leaves and chop, mash, or pulse in a food processor.
- Pour 2 quarts of boiling water over them and allow the tea to steep overnight.
- Strain off willow tea and fill sprayer with full-strength tea or dilute it 1:1 with water.
- Store in the fridge. Spray plants in the early morning or pour directly onto soil around seedlings or stressed plants.
Essential Oil Spray
To a quart of water, add 1/2 tablespoon of peppermint oil, cedarwood oil and/or neem oil (also known as tea tree oil or melaleuca), and 1/3 teaspoon liquid soap (Dr. Bronner’s), which also works as an emulsifier.
Fill a spray bottle with a spray recipe of your choice and spritz the soil and the inside edge of the container or pot. Spraying the plant itself is not as critical because unlike aphids that tap into the soft tissues of leaves and stems, fungus gnats take flight (often when disturbed) and tiptoe in and around the soil.
We all know that beer and Sluggo work wonders for dispatching adult slugs. But not baby slugs, those sneaky pests that can riddle a plant with gunshot-size holes overnight. (I’m still experimenting with this application. I will keep you posted).
To 1 quart of water add:
- 20 drops cedarwood, pine, or hyssop essential oil
- 1/2 tsp. Epsom salts (first dissolved in warm water to emulsify the essential oil)
Seaweed has been used by gardeners and farmers for thousands of years. Applying it as a spray is a quick way to feed plants–and seedlings–to boost their health and help them deal with environmental stresses.
There are dozens of recipes for kelp spray. The easiest and quickest is to toss a handful of “clean” kelp (minus rocks and sand) into a blender half-filled with water. Process, strain (through a filter such as a coffee filter), and dilute to a light tea color, before loading up a spray bottle.
All-Purpose Pest Spray
Add 2 teaspoons of Neem oil and 2 teaspoons of liquid soap such as Dr. Bronner’s Peppermint soap to 1 quart of lukewarm water. Gently invert a few times and remember, try not to foam it up by shaking.
3. Sticky traps
Sticky traps are my favorite anti-gnat solution. They’re just a card, usually yellow, that’s coated with a sticky goo. You can buy sticky traps or make your own. It’s easy. Here’s how:
Color is the bait, and pests prefer yellow. The source of the yellow color is not important. So long as it’s bright yellow, it can be made of:
- Paper card stock
- Flexible cutting boards
- Plastic or paper file folders or plates
- Painted wood
The base material: For indoors or in greenhouses and other protected garden areas, paper or card stock may be OK for one-time use traps. For outdoors though, make your traps sturdier. Maybe coating a rubber ducky would work? Thing is, with a little bright yellow paint, pretty much anything will do, from plastic milk jugs to aluminum cans inverted on a stick.
The sticky goo: If you can’t find commercial sticky coating such as Tanglefoot, again, you have options. Simply apply a layer of petroleum jelly or a thin coating of motor oil to the base surface. The oil isn’t as sticky, but it’s sticky enough to capture pests. Just remember, sticky traps also capture beneficial insects, so check on them frequently).
After positioning your traps, in a few hours, you can start counting the casualties. Though I highly recommend removing the sticky trap from sight if you have guests coming over for dinner.
As for things that irritate you, I remember reading a story about a young man who was sitting in a circle with other students, listening to their guru-teacher discuss how to be “in this world, but not of this world.” As the night drew on, so did the mosquitoes. Soon all the students were waving their arms, swatting at the intruders.
“Why are you fidgeting so?” their teacher said sternly. “Is the whole world going to change for you? Change yourself. Be rid of the mosquito consciousness.”
Whoa, Nellie. Now there’s an interesting way to get rid of pests.
Thank you for visiting! Cheers to you,
P.S. Slowly but surely I’m posting over 1,200 of my weekly gardening articles, which you can access here. And if you want to amp up your composting game, be sure to check out my report: “220 Things You Can Compost.” To contact me by email: marion (at) marionowenalaska.com.