Damage looks too large and isolated to be white flies, more likely beetles, some sort of worm (moth, butterfly or similar larvae), leafhoppers, leafcutter ants, etc (or some combination, need not be only one villain in a garden). I don't know which pests are native to your area.
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One thing about BT, as far as I know it doesn't kill them quickly on contact so even an insect it ends up killing, could land, eat for a while, then fly or crawl away. It could be that you are decreasing the number of pests in the local vicinity but not fast enough to be ideal.Â
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In that kind of situation, consider spraying the perimeter of the grow area - grass, weeds, whatever encircling them, or switch to something with higher immediate toxicity like chemical insecticides then only apply those to the pepper plants.