Whitefly on Aspidestra plant
We do have a couple of products that will help you with the white fly aphids on your Aspidistra (Cast Iron plant).
I would try Sticky Pest Traps first, as they are cheaper to buy and should do the trick. They are designed for hanging in a greenhouse to attract all common greenhouse pests including whitefly but will work in the house too. What you could do is to shake the plant and either hold or stand a sticky trap beside it so when they fly off the little critters head for the yellow traps. They are supplied in Packs of 10 so will keep you going for a while.
In addition you could spray your plants with Organic Savona Fatty Acid Concentrate - this is sold in a 1 litre concentrate bottle and you may think it expensive to use on one houseplant but it is a useful product to have for many greenhouse and garden pests. It’s safe to use with care around children and pets and won’t leave any harmful residue on the plants so it’s good for the environment too.
Either way I hope you get the problem sorted soon.