Are these plants in the ground outside, in containers outside, inside? Managing aphids works best if you can combine a few methods. If the plants are outside, then there are aphid predators like ladybug larvae that will take a bite out of them, but that won't work if they can't get through the mesh. I don't think mesh works on aphids. Regular, repeated spraying of Neem oil and/or insecticidal soap will knock the numbers down quite a bit. Just make sure that you spray both the top and underside of the leaves as well as the stem and that you don't spray in the heat of the day or you might burn the leaves, and if you use both treatments spray with one, wait a couple of days, then spray with the other, wait a couple of days, then repeat. You have to do the cycle of treatments more than once in order to interrupt the aphid life cycle. And if you see beneficial insects, spraying will potentially hurt them, so check first. Try to avoid spraying open blossoms if you can. Whatever you choose, take the time to read the labels twice. Aphids can also be drawn to high nitrogen (hence why they really go for new growth first) so you may want to cut back on the fertilizers.

Hi thanks for the reply sorry if my post was a bit short. No there in a greenhouse in a tray I made a lift up frame with netting on see the photo. I tried to grow a chili plant last year in the house but it died from a bad case of aphids so we bought our 1st greenhouse and started to grow a few different types of chilli but the loco plant is ahead in growth and starting to get flower buds and a lot of aphids are on it this is why I'm worried that the same thing will happen again thanks

I just want to have a nice crop of chilles these thing are a right pain in a$se

I feel your pain. Last year I had such a bad infestation on my pepper and eggplant seedlings I didn't think they'd live long enough to get them outside and planted. It took me a month of spraying 2-3 times a week to get the numbers down somewhat. Once I got them outside they didn't seem to suffer as badly, but the plants I chose to grow in containers still needed spraying 2x a month. You have to realize that the growing plants inside is like aphid utopia - no temperature extremes, no wind, no competition, no predation, constant food source. They only have to worry about making more aphids. The best you can do manage their numbers and focus on growing robust, healthy plants since a healthy plant will not be as affected by aphids as weak one.

Ladybugs or green lacewings will take care of your aphids

The best technique is manually knocking them off with water and then treating with neem. If you do this a couple of times they will be greatly diminished if not gone.

Hold the plant sideways and spray all over with a strong spray of the hose. I hold the plant sideways so the aphids don't drop onto the lower leaves. Make sure to get under the leaves too.

Then do a neem treatment overnight. Don't apply neem in the day or the plants can burn as it is an oil.

This definitely works.

How often would you use the neem and would you continue to use it for as long a the plant is alive

The aphids I experience are typically only a big problem indoors. They can get bad outdoors too but they only seem to last for a relatively short period of time when they do get bad out side. I think it is generally in the spring. I have never had them be an issue all season long.

I would keep up the neem every week or so until they are almost gone then maybe stretch it out a bit. Neem also has also healthy benefits for this plants so it's a good tool all around and makes the leaves nice and glossy and green.

Esox is right, aphids usually disappear once they go outside, but they can kill seedlings and stunt new growth so stamp them out while you can!