The main pests encountered are aphids and whitefly. The problem with these is that they suck the sap and this distorts the leaves. They also secrete a sticky substance called honeydew, which fall onto lower leaves and then "sooty mould" forms. This stunts the leaves and subsequently weakens the plant and fruit.
Sadly, these pests are really difficult to control as they are becoming immune to most pyrethoid bug killer sprays. Organic control by using predators is a bit of kidology as total control is never achieved. Apparently, the objective of these is to be environmentally friendly, live in harmony etc. Meanwhile your chillies still get stunted.
Nevertheless, it should be tried by the Organically minded growers who will accept some losses.
I have found that the best control method is to hang some sticky yellow "Greenhouse fly catchers" cards between the plants. The bugs then tend to go for them and get stuck before they can get to the plants. I have also had some success with a spray called "Rapid" on Red Aphids. This spray allegedly, doesn't harm bees