Is it possible to use DE on C&G plants?
Like covering the surface of the soil with DE?
Sprinkle DE on the plant to kill insects?
Will it harm the plants?
I haven’t used DE on my plants before, however I did choose NOT to use DE when I got a small ant infestation in my home last summer. Instead, I chose to use lines of cinnamon where most would have put lines of DE. I also used cotton pads soaked in essential oils from orange, lemon, tea tree, and peppermint. These all helped to repel the ants. I imagine, if you’re ready to put DE on your plants, your pest problem must be very frustrating. I would consider doing a little more research into more gentle pest repellents before using DE on your plants. Some plants themselves are natural pest repellents such as peppermint and lavender. Which is 1 reason I have both in my garden currently and I will most likely continue to use both. 
Food grade DE is non toxic and even “edible”, why would it not be recommended?
In fact, I’m considering it to be the first choice before other “chemical” means, even thou the chemicals are all of natural origins (essential oils etc…).
I’ve got encountered mint infested with aphids (which are defended by ants, their ally), so I doubt mint or pepper mint repel ants… and it’s difficult to tell which oil works or doesn’t work (unless you already have the oil to test it without having to buy it)
DE works by physical means. There’s no chemistry involve and it’s much simpler. And there’s no worries of chemicals messing up the pH or mineral balance in the soil.
I have considered neem oil but it appears that in my country its either not easily available or too expensive. (local vendor markup 100~200% compared to prices in the US, for example).
Essential oil also can expired so… not so convenient for long term storage (keep on standby in case of potential pest problems).
Fair enough. It sounds like you’re going to use it so post pictures and updates when you do because I’m curious about results. 
I’m just curious to hear from those who are experienced or from C&G plant experts of their opinion on DE.
I have very limited exposure to plants and gardening… What I wrote is what I read about DE only. The impact on plants is really unknown. Hence would appreciate if C&G can comment or maybe try some experiment with it with their vast resources and expertise available.
I did try before dusting DE on a pot of mint and pandan. There isn’t any noticeable harm to the plant, expect that the leaves are covered in white dust. The dust is not applied evenly as I do not have the appropriate tools for it. I am guessing the pest control is not effective because it didn’t really get to the ants or the aphids.
Next time I will mix the DE into the soil or cover the soil surface with it when potting or transferring a new plant.
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Hey! What exactly do you mean under DE?
Diatomaceous Earth.