So what actually kills aphids?

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There is something wrong with this entire scenario. Are you telling me that soaps and Neem did not kill them at all? That they are impervious to the chemicals? If so then I would have to say that by spraying generations of the aphids in an enclosed environment that they have built up an immunity to the chemicals and if this really be the case any research facility will pay you good money for access to your plants and your aphids in order to study and develop insect resistant pesticides. Pyrethrin is one of the most lethal organic pesticides in existence, even stronger than most synthetic insecticides and if that doesn't kill aphids there is something definitely off about this entire thing.
I don't know what to tell you except to start over. New containers, new soil, new seeds, new everything. And also this. Aphids are attracted to stressed plants and for some reason your plants became stressed which is why they showed up in the first place.
Soap & neem did nothing from the first application, so it has nothing to do with building an immunity, unless they developed one before moving in here.
 
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I'm using 4x because I started at 1x and it did nothing. You think I just jumped in and said f** these instructions, I'm making it stronger...? I tried it first as directed, absolutely 0 result.
I didn't really think that, but there are those who would think 'I have tried other things, I'll try making it strong'. No way am I saying you are one, but you must admit there are plenty of people about who do have strange ideas, so just making sure.
 

NigelJ

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I'm surprised any of your plants are still alive with all that drenching.
I would go back and follow the instructions on the concentrate pack regarding strength and frequency of application. There are frequently other chemicals in the mix other than the active, for example wetting agents and solublisers. At too high a concentration the droplets may just run off before having an effect, or you may get uneven application.
The instructions are there for a reason and using higher strengths you are just wasting money.
Mechanical removal, finger and thumb works, wear gloves if squeamish.
 
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Mechanical removal, finger and thumb works, wear gloves if squeamish.
Or even a nice soft shaving brush that won't hurt the plant :)

There was a comment earlier about their jaws being locked onto the plant, so they stay there even when dead. Could it be that most are dying, but don't look dead and are then replaced by rapid reinfestation?
Could something else be supporting a small population locally?
 
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If aphids can live happily in an indoor environment could ladybirds/ladybugs? Would introducing predators work in your situation?
Or perhaps better still - nematodes! I've only ever used slug and vine weevil nematodes but they work a treat. You can indeed get aphid nematodes. The are essentially a predator - the tiny nematodes lay eggs in the aphid, it hatches and eats the aphid from inside, then finds another aphid to lay it's eggs in. So it's a bit like a plague running through the aphid population that won't stop until there are no aphids left.

 
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There was a comment earlier about their jaws being locked onto the plant, so they stay there even when dead. Could it be that most are dying, but don't look dead and are then replaced by rapid reinfestation?

Sometimes there are whitesh bodies after a soap spray but they are dead so they are very stubborn. Flipping them with afinger reveals they don't move. lol.
 

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If aphids can live happily in an indoor environment could ladybirds/ladybugs? Would introducing predators work in your situation?
Or perhaps better still - nematodes! I've only ever used slug and vine weevil nematodes but they work a treat. You can indeed get aphid nematodes. The are essentially a predator - the tiny nematodes lay eggs in the aphid, it hatches and eats the aphid from inside, then finds another aphid to lay it's eggs in. So it's a bit like a plague running through the aphid population that won't stop until there are no aphids left.

Aphidus are a small parasitic wasp not a nematode (despite being sold by nematodesdirect). A good idea though, they won't get rid of all of the aphids, but will significantly reduce the numbers.
OP will probably need to find US supplier though.
 
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I'm surprised any of your plants are still alive with all that drenching.
I would go back and follow the instructions on the concentrate pack regarding strength and frequency of application. There are frequently other chemicals in the mix other than the active, for example wetting agents and solublisers. At too high a concentration the droplets may just run off before having an effect, or you may get uneven application.
The instructions are there for a reason and using higher strengths you are just wasting money.
Mechanical removal, finger and thumb works, wear gloves if squeamish.
I followed the directions, it did nothing. Wow, these forums are completely useless. Not one person has answered the question: what kills aphids?
 
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My old shaving brush and a bar of the cheapest, softest soap seems to do it very well. It knocks them about and drowns them at the same time. I repeat shortly after to get those I missed, don't want survivors who may build some sort of tolerance.
Susan pointed out that it is stressed plants that get attacked, they spot a weakness and go for it, could it be that growing indoors creates unnatural conditions that make the plants more vulnerable?
It kills them, the bristles are stiff enough to damage the aphids but not the plant. Use actual soap, not 'dish soap', it then gums up their breathing holes, that kills the ones that survive the bristles.
 
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I followed the directions, it did nothing. Wow, these forums are completely useless. Not one person has answered the question: what kills aphids?
This will definitely kill them.
 
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I followed the directions, it did nothing. Wow, these forums are completely useless. Not one person has answered the question: what kills aphids?
Actually, a lot of people have answered. The fact that what works for everyone else doesn't work for you is hardly our fault!
 
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I use 1 to 1.5 tablespoons of Dawn Ultra per gallon of water and it has always worked for me. If you try the Great Value brand or castile soap then it will have different chemicals or more water so you would have to change the dose or that brand may not even work. I'm not sure about a different type of soap but I think Oliver is saying to use a brush and brush a bar of soap and then brush the insect.

I have also used sevin dust liquid and malathion before and it killed them but I do my best to not have to use those things. Sevin dust (the actual dust) may work better because the dust will lay there and continue to kill if you can get it applied to the underside of the leaves.

I'm pretty sure none of the insecticides work on their eggs so if you spray and kill the live insects, the eggs hatch later and it appears that nothing has happened. You should spray, then later spray again to kill the eggs that hatched. Timing is key. Here is something that says aphid eggs take 7-8 days to hatch and they can be born pregnant, which I didn't know, so again timing of the spray is very important if you have a problem like you have.
 

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