I think the sand probably works because the surface dries fast. Fungus gnats are only a problem if the top of the soil stays damp enough for them. You'd probably do just as well by watering less often. Fungus gnats are a pretty sure sign you're keeping the plant too damp.

I'm sure water will penetrate the sand without any trouble, but added sand might reduce the amount of oxygen penetrating the soil, and the reduced O2 could theoretically raise the risk of root rot in a plant that's already a bit wet.

If it were my plant, I'd replace the top few inches of soil, wait for the top few inches to completely dry between waterings, and maybe place some fly paper around the base of the plant for a while to catch any remaining gnats.

As noted, the gnats are a symptom of a more serious (to your plants' health) underlying problem that centers either on soil choice or over-watering. Many would be quick to dismiss the issue as a symptom of over-watering only, but it's more complicated than that. Soils that can't be watered to beyond saturation (so you are flushing the soil when you water) w/o having to worry about gnats and your soil staying soggy so long it affects root function/health, are soils you'll constantly be battling for control of the vitality of whatever you plant in them. Neither a premium price or attractive packaging with plenty of promises are reliable indicators that what's inside can deliver the goods.

Al

It's possible the grower may have over watered the plant, but I didn't. I repotted it immediately after purchase and five days later I saw the gnats. They were probably already present when I bought it. It seems it's impossible to buy "clean" plants anymore.

The idea that the sand may hold in moisture is a reasonable idea. I think wait a few more days for eggs/larvae to die and remove the top soil layer as suggested here, replacing it with fresh potting mix. I'll see about the sticky traps. Someone also suggested a Bt powder that kills larvae. Thanks for your input.

We've had enormous problems with Fungus Fly - in our experience it's rarely a problem caused by the plant's owner/carer but almost always in newly sourced plants/new compost.

We've taken to using predator bugs (successful) and also an apparently very good fungal disease supplied in the compost called MET52. The only problem we've had with the latter is it is static, i.e. if we get fungus fly in the rootball, the MET52 in the soil doesn't infect it.

Using mosquito dunks in the water given to plants can get rid of them. This discussion covers it well.

Since eliminating peat, I haven't seen them around my plants.

I bought my majestic palm from Costco it looks like there are two palms in this pot, I was wondering how to separate them and re pot them into to pots, also I see tiny gnats flying around the base, what do I do to get rid of them?

Carolyn- in all fairness, the fungus gnats were probably in the soil when you bought it, or it came in potting soil in a bag if you repotted the plant. I've also seen them flying around the plants at some of the big box stores.

I don't have a good solution other than letting plants dry out a lot between watering and spray the soil with insecticidal soap twice a week for several weeks in a row. You could also try sticking a bunch of garlic cloves into the soil too as an additional deterrence. Gnats hate that.

Diatamaceous earth helps kill larvae, and potato slices cut side down will serve as traps for you to collect and dispose of large numbers. I agree with everyone on drying out the trays, and plan on experimenting with mosquito dunks myself but such things are not always possible. I have had great success with the DE and potatoes in a research project with some 200 flats at my university's greenhouse where chemicals and dryouts were not an option. A palm shouldnt be left wet enough to sustain colonies of them long, likely with proper care in your home it will resolve itself.

I have several plants that are a little trickier in care, and mustn't be allowed to dry out. The wettest ones occasionally crop up with a few gnats especially in the summer, but I now have lovely little Cape sundew is now completing that circle of life.

Great information above. Fungus gnats are an insidious pest and love wet soil, especially with decomposing organic matter ... it's where they lay their eggs. While you're focused on eradicating the actual flying insects, they are busy laying their eggs in the soil, and there's a generation of larvae that have already hatched and are creeping around in the soil. So it's flying insect, larvae, eggs. That's the Insidious part ... While you're getting rid of one generation, the next generation is hatching.

I had a similar problem. Fungus gnats were coming into my living room right through the window screens. My neighborhood a grapevine below my window and there's nothing I could do to make him get rid of it. The problem got so bad that they were biting me on my face.

Here's what worked for me. I purchased sticky traps and, as unsightly as they may be, they work. I learned to bottom water my plants. Never water plants from the top ... It keeps the upper surface of the soil too wet. Next, I peeled and sliced (about half inch thick) a raw potato and placed the slices on top of the soil. The larvae actually burrow into the wetness of the raw potato. You can't see them but they're there. You have to discard the potato slices after 2 days and replace them. Now for the eggs and to prevent the problems from ever recurring, you have to purchase and apply a systemic. I use Bonide, which is a powdered systemic that is sprinkled on top of the soil and watered in. A systemic works its way through the roots into the structure of the plant and makes the plant resistant to most pests. I use this product on all my non edibles.

This process worked for me within one week and eliminated all fungus gnats from my home within 2 weeks. I still used Bonide on all my potted plants.

Mixing diatomaceous earth in the top inch of soil has worked for me to eliminate them.

A product with BTi as the active ingredient, added to the water given to plants when thristy will eliminate the larvae. There's no need to use anything stronger than this naturally-occurring bacteria.

Sold as Mosquito Dunks and Mosquito bits, safe around pets, people.

Repotting is always a great option.

Gnats can fly, so they can come inside any time a door is opened, and are not a pest of plants, just the soil in which they live. Getting rid of peat has also eliminated fungus gnats for me.

Carolyn, Hi & welcome to GardenWeb! If you are able to start a new discussion about repotting your palm, you'll almost certainly get more relevant responses. Adding a pic always helps too.

Thank you for the advise on the gnats, I separated the two palms and repotted them with new soil and I haven't seen any gnats lately.

Now the issue is browning and dry out fronds with new shoots sproting, I did move them to indirect light and misting daily, I hope that works.

Good Morning!!

Thank you all for sharing above albeit four-six years ago I’m late for the party! I bought two majesty palms from ikea a few months ago. Turns out that my plants both have spider mites and I see an infestation of some sort on top of the soil of one. I have been 1. spraying each with alcohol and then 2. wiping each leaf front and back with a spray mix of dish detergent and water. I’ve done this about every three days for a few weeks. Now this morning I noticed a bandit yellowing branch. Upon looking closer I see what looks like webs in the soil and gnats flying near the base. I’ve put lots of care into these babies. What should I do? Sand, repot? How do I bottom water? Systemic? Help!

Cut your losses and return them to the store & get a refund. Let them know that they are selling pest infested plants.

If the post was current, I'd say: #1 suggestion would be to stop using any household cleaner (dishsoap) as a way to clean leaves or in an insecticidal capacity. See something I wrote about it below. BTW, disregard any argument that goes something like "I've been doing it for years and have noticed no adverse effects ......". The fact is, it destroys cuticular wax, and if it gets to the roots, root lipid membranes. So, it prevents or limits roots from taking up water/nutrients, and destroys the mechanism by which plants limit water loss from their foliage and protect against insects and entry of pathogens. If you need a product to clean leaves or to use as an insecticide, insecticidal soaps are made from long chain fatty acids, formulated to be safe for most plants, though there are a few plants sensitive even to insecticidal soaps.

A mix of 70% isopropyl/rubbing alcohol and water at 1:1 or 2:1 (2 water: 1 alcohol) if all you need for mites. Spritz the plant thoroughly at 4 day intervals, making sure you coat the entire surface of the plant, including inferior leaf surfaces and and leaf axils where they tend ti hide in the dark.

A change in watering habits or a change in your grow medium are usually all you need to be rid of gnats. Unless your pot is 5" deep or less, avoid the advice to water when the top inch or two of the soil is dry. It's a recipe for over-watering and the very idea is enough to make a gnat's eyes spin in anticipation of the orgiastic frenzy induced by media the surface of which provides a never ending supply of wet/rotting organic matter.

This should be helpful, as would be changing to a highly aerated medium, the surface of which dries quickly, and using a "tell" to "tell" you when it's time to water.

Detergents

Dishsoap/ detergent’s effect on plants varies with the mode of exposure. Dawn, Palmolive, Joy, ...... dishsoap, as an example, are each and all a mishmash of chemicals, at least eleven of which are phytotoxic. If the top of the plant is sprayed thoroughly with even mild detergent solutions such that all surfaces including leaves are covered, the detergent can easily dissolve the protective coating of cuticular wax on the leaves of the plant, causing abnormally high rates of water loss and possible necrosis of all or part of the leaf. Cuticular waxes prevent leaves from drying out, and help stop pathogens from attacking the leaf. Strong solutions will even dissolve cell membranes, causing death of the cells.

If a detergent solution is used as a soil drench or makes its way into the soil as a consequence of over-spray or run-off, the effect on roots is immediate. Because one of the main function of roots is to absorb water and nutrients dissolved in water, they lack the waxy protective coating that leaves employ. Detergent solution in contact with root cells can quickly dissolve the lipid membrane surrounding cells, killing the cells and inhibiting water/ nutrient uptake. Hair cells growing as appendages off larger roots do the lion’s share of assimilating water and nutrients, and these very delicate cells would be the first casualty of any detergent in the root zone.

There are widely available insecticidal soaps, designed to be used topically and made mixing potassium with only long chain fatty acids, carefully selected and specifically formulated to be safe for mammals & birds, death on most insects they contact, and most important, safe for plants. If you need something "soapy", it would be much better if you selected a product intended for use on plants than one intended for other purposes.

Using a 'tell'

Over-watering saps vitality and is one of the most common plant assassins, so learning to avoid it is worth the small effort. Plants make and store their own energy source – photosynthate - (sugar/glucose). Functioning roots need energy to drive their metabolic processes, and in order to get it, they use oxygen to burn (oxidize) their food. From this, we can see that terrestrial plants need plenty of air (oxygen) in the soil to drive root function. Many off-the-shelf soils hold too much water and not enough air to support the kind of root health most growers would like to see; and, a healthy root system is a prerequisite to a healthy plant.

Watering in small sips leads to avoid over-watering leads to a residual build-up of dissolved solids (salts) in the soil from tapwater and fertilizer solutions, which limits a plant's ability to absorb water – so watering in sips simply moves us to the other horn of a dilemma. It creates another problem that requires resolution. Better, would be to simply adopt a soil that drains well enough to allow watering to beyond the saturation point, so we're flushing the soil of accumulating dissolved solids whenever we water; this, w/o the plant being forced to pay a tax in the form of reduced vitality, due to prolong periods of soil saturation. Sometimes, though, that's not a course we can immediately steer, which makes controlling how often we water a very important factor.

In many cases, we can judge whether or not a planting needs watering by hefting the pot. This is especially true if the pot is made from light material, like plastic, but doesn't work (as) well when the pot is made from heavier material, like clay, or when the size/weight of the pot precludes grabbing it with one hand to judge its weight and gauge the need for water.

Fingers stuck an inch or two into the soil work ok for shallow pots, but not for deep pots. Deep pots might have 3 or more inches of soil that feels totally dry, while the lower several inches of the soil is 100% saturated. Obviously, the lack of oxygen in the root zone situation can wreak havoc with root health and cause the loss of a very notable measure of your plant's potential. Inexpensive watering meters don't even measure moisture levels, they measure electrical conductivity. Clean the tip and insert it into a cup of distilled water and witness the fact it reads 'DRY'.

One of the most reliable methods of checking a planting's need for water is using a 'tell'. You can use a bamboo skewer in a pinch, but a wooden dowel rod of about 5/16” (75-85mm) would work better. They usually come 48” (120cm) long and can usually be cut in half and serve as a pair. Sharpen all 4 ends in a pencil sharpener and slightly blunt the tip so it's about the diameter of the head on a straight pin. Push the wooden tell deep into the soil. Don't worry, it won't harm the root system. If the plant is quite root-bound, you might need to try several places until you find one where you can push it all the way to the pot's bottom. Leave it a few seconds, then withdraw it and inspect the tip for moisture. For most plantings, withhold water until the tell comes out dry or nearly so. If you see signs of wilting, adjust the interval between waterings so drought stress isn't a recurring issue.

What I use for grow media:

Al