Diatomaceous earth for root aphids

Do you need to put diatomaceous earth in the soil when you transplant to stop them? I’m assuming putting it on the top of soil won’t get them since they are down in the roots? Seems like I got a bag full of them and one of my plants that is in a 5 gallon seems to be nutrient deficient right after transplant so I’m assuming the aphids got to it.

Pyrethrin root drench is what I see being a solution

Nematodes, amigo. Nematodes.

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