1) Less organic matter in your soil mix

2) a heavier (thicker) layer of top dressing

These two things would preclude you from having to use a systemic, or for that matter, any type of insecticide. Poisons are too often used when the thing to do is change the culture.

I would agree ... first order of business would be to reduce the organic matter in your media. Tropicals and some other houseplants may benefit from a highly organic media, but most cacti/succs don't.

What you can try using to kill the gnat larvae off is a product containing Bacillus thuringiensis subspecies israelensis. (B.t.i.), a bacteria that will kill off the larvae when they ingest some of it. It is frequently available in what are called "mosquito dunks" (at least over here). Just break off a quarter of a "donut" and soak it overnight in the water to inoculate it before using that water to water your plants. The chunk can be reused until it disintegrates.

Also agreeing with above comments, if you see some flying around just spray them right away with 50% rubbing alcohol just to slow the reproduction cycle at each step because nothing is full proof. Also good ventilation helps blowing them away. You actually would have to have a pretty major infestation for it to affect mature plants. It's a very different deal if you grow seedlings. A few larvae can chew on them and leave you with empty shells overnight!!!

Check out the like below. I’ve used something like this before to catch the adults as they are flying around. No adults, no mating. No mating, no eggs. No eggs, no larvae.

https://www.amazon.com/gp/aw/d/B07HJ6PZD5/ref=sspa_mw_detail_0?ie=UTF8&psc=1

Tyler

Thanks guys. I'm in the process of changing my mix from totally inorganic to a mix that's mostly perlite with some c&s potting mix and some stones mixed in for weight. I do have just a few plants that are in their original old soil. I'm slower at repotting them now because I keep having to repot the ones that are dying from the bugs. Atm it's the only way I can keep them alive. I don't have seedlings but just as tiny plantlets from some Kalanchoe plants. They are the main ones that are dying, but other tiny plants are dying too if I don't keep repotting them. Some tiny Sedums with really tiny fat leaves and a couple of purple blobs. Most of all those plants have died :-(

Also some bigger plants have been deteriorating slowly so I've repotted some of them and they perk up again, for a while.

I guess I'm going to have to have a huge repotting session.

I'll check out the BTi first and when I've got enough pots (and enery) it'll be on.

With the good pots are they able to be cleaned of the bugs including the eggs?

Again thanks

Was not aware of the BTI thing, going to give that a try.

Thankz Gees. All my plants are on my 2nd story balcony except any that I've just repotted. But I can put them out in a small shady area, or make some shade if needed.

I've only seen one adult in the last week or so - after I started the dishwashing liquid drops and canola oil drops in a bucket of water, then using that mix to water all my plants. Maybe that worked better than I thought. Should I try that again?

But first I'll let them all dry out. We are having temps of high 30°Cs & low 40°Cs almost constantly so I need to be careful.

I don't mind using insecticide if needed, but the systemic stuff is so potent that it kills any creatures that take any in (depending on size probably), including anything that feeds on any part of the poisoned plant. So that would include bees, birds etc. But the info I found said dont let it go into the general garden or the drains (kills fish) and had more warnings.

The most common source of fungus gnats is bagged soil. The solution is to bake it, microwave it, or simply open the bags and spread it out in the sun on hot, dry summer days. Good luck!

In my experience the most common source of fungus gnat grubs, which cause the damage, is fungus gnats. Having said that, avoid the use of peat, which attracts them, and grow outdoors. They are poor fliers and get blown away in the wind.

Didn't read all posts so forgive me if repeating what was said already:

Adult females have short life span, but will lay hundreds of eggs, in the soil, in few days. After that, they will die. Adult males have even shorter life span. Not much works on adults, best is to catch them using sticky tapes. They can be annoying, flying into your nose, eyes...but do not eat plants.

Best is to eliminate larvae: they live in soil, feed on organic matter. They love moist, humid environment. Making sure those conditions are not available will eventually eliminate them by starving. (That is why growing succulents should be having extremely small gnat population, if any). Using BTI/mosquito dunks in water is great help. Adults will not kill your plants, they just fly around. Larvae will feed on organic matter in soil, sometimes also roots, but there would have to be quite large infestation to kill plants. There is no need for any systemic. If you watered plants with canola oil in the water, it probably smothered some larvae, not adults. I do not have any gnats (having few hundred pots including some tropicals, indoors for the winter. These get watered more often and have more soil with some bark in the mix. Almost all these have top dressing of turkey grit = bigger than chicken grit used in mix for succulents). I do not even own any sprays/systemics, if I need to get rid of occasional mealy, I use rubbing alcohol.

Rina, thank you so much for coming in on this thread. I appreciate and value your feedback.

I'm in the process of drying out all my plants. They were wetter than I thought.

I have bought a non sytemic poison that was recommended at Bunnings. They also told me that the main products I was worried about are not available in Australia anymore. But it's still pretty potent.

I would prefer to try the mozzie dunks first though so planning to look for some today. Will be 42°C so hope it doesn't take too long :-/

Again thankyou :-)

A sprinkling of diatomaceous earth (DE) on the surface of the compost is supposed to be effective for this, also effective against mealy bugs, available in 2 kg bags on Amazon here in UK and fairly cheap. Also comes in tubs (food grade) in health shops but that’s more expensive. DE has mainly been used previously by keepers of chickens to control mites and other parasites, but people now beginning to wake up to horticultural uses. I just bought some and intend to try out this coming season. The only issue with DE is it’s a very fine powder and not advisable to breath the dust into the lungs so wear a mask if using a lot of the stuff.

Thanks Andrew, I think I've got that but in small chunk form. If it is I could break it up to sprinkle on top.

I don't think so. My understanding is that the granular stuff (turface etc) has been heat treated in order to modify the structure and it won't be effective against bugs.

Yeah your right it's partly fired. Well mine is. Mine is called something like Attapulgate, but when I was researching it before I bought some, I found that it had many weird names. And diatomaceous earth sounded very familiar. it also wasn't on the bag when I checked.

Systemic is overkill for fungus gnats when BTi (mosquito dunks) work very well. Systemic is also quite expensive and bad for the environment when better substitutes are available for this.

I'm in agreement with that one. Except for a couple of big ones, all the pots are bone dry, so I'm hoping my son will take me to Bunnings tomorrow and get the mozzie dunks and while I'm there get some soap.

Helen

What kind of 'soap' are you thinking of?

I was hoping to find the one you use that kills or reduces bugs without harming the plants and the environment.

Insecticidal soap is just a type of soap with longer molecular chains to reduce the potential for damage. It can still damage your plants! It works by drying out the skin, presumably larvae in this case because soap spray may not do much to the fliers.

I do not use ('sops') soaps (sorry for misspelling...). But to make any home-made concoction, use vegetable based soap, not detergent as often suggested on net. Or use what ewwmayo suggested - insecticidal soaps (I had used this years ago, on scale on ficus Benjamina, but do not any more). They are sold in spray bottles & are ready-to-use. Much better than detergents, but still could cause some damage. Remember to keep out of direct sun if spraying with anything (that includes rubbing alcohol).

You can also buy it in concentrate form, which is a little cheaper. Yes, there is no guarantee it won't damage (and it has happened to me before).

Insecticidal soap is harmless to plants and kills flying gnats on contact.

Ewwmayo, I haven't seen any fliers since I started this thread and only one in the days before. So I'm assuming that the life cycle is stopped. Just wanted to make sure that any larvae couldn't survive, in case there were some eggs left that might still hatch.

Also I wasn't sure what the soap was called or made of that some here advise to use instead of dishwashing liquid. I wasn't going to use it, just have it on hand in case of an uncontrollable outbreak. And even then get some more advice on how or whether to use it.

Rina, ouch! That really hurt :-( Not so much that you missed what I meant, but the way you responded. Like "sops" and "home made concoction".

If the soap you would prefer to suggest is vegetable based then that's what I want in my "just in case shelf".

I realise that I'm frustrating to many people including in this forum and I appreciate all the help I've been getting.

Anyway, I know I can get the mosquitoe dunks in Bunnings, but do you think they would be likely to have the veg based soap in their garden section? Or maybe a supermarket?

Helen

That is misspelling! I usually proof-read what I write since my English is not that great, but missed 'sops'. I am sorry you misunderstood. And there is nothing wrong with 'home-made concoctions' - that is exactly what they are. I have seen that expression used a lot (and made some concoctions few years back too).

I do not know what are the names/makes of vegetable-based soaps sold in Australia, but there are many. Common is Castile soap (read about it HERE ). Or any others. Here are couple from my bathroom:

Thanks for clearing up that misunderstanding and helping with what sort of soap. I think I must be feeling a bit sensitive because of things happening in my family :-/

Rina thats a great link to the oil/soap and what it does. Thankyou :-)

Helen

np. Jut want to make sure you know that I wouldn't say anything to anyone but what I find acceptable to be said to me (hope this sentence makes sense :)

Hope everything turns out well with your family. And plants too.

Thanks rina, that was nice of you to tell me :-)

I'm hoping all will be sorted next month. We are having a big bash birthday celebrations. This year my daughters (twins) turn 40, my sister turns 50 and I turn 60 lol.

As for my plants, I've just found that the Aeoniums have got a different pest.

At the moment I can't deal with it, so I'm going to bed.

Yeah for all my friends on this forum!!!!

I didn't use any anti bug stuff, just let all the plants dry dry dry.

I reckon 99% of the plants survived. Some were even getting new growth before I started watering them again.

And I think the damaged leaves were from sunburn after using the watering mix I'd made up. So whoever suggested that was correct .

Thanks to all who helped and encouraged.